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        Zoonotic Diseases


        Anna Rovid Spickler

        , DVM, PhD, Center for Food Security and Public Health, College of Veterinary Medicine, Iowa State University

        Last full review/revision May 2015 | Content last modified May 2015
        Topic Resources

        Global Zoonoses a lists zoonotic bacterial, viral, fungal, and parasitic diseases, grouped by category. Many proven zoonoses, including some diseases that are rare in people, organisms that are maintained primarily in people, some primate diseases, and diseases caused by fish and reptile toxins have been omitted. The table is intended to give a general clinical picture of each disease; current medical texts or review articles should be consulted for a more complete description. Clinical signs are listed; asymptomatic infections can also be assumed to occur in most cases. An indication of the mortality rate among healthy individuals has been provided for many infections. However, there is almost always a chance of death whenever lesions can become generalized, vital organs may be affected, secondary infections occur, and/or the patient is immunosuppressed. The mortality rate is often influenced by the availability of medical care, and it is generally lower when advanced medical support is available. The risk of death from some bacterial diseases with high mortality rates can be nearly eliminated with prompt antibiotic treatment.

        If a disease is known to have unusual manifestations or to be particularly common and/or severe in immunocompromised people, this has been noted. In addition to these diseases, many pathogens can cause more severe disease and/or unusual signs in immunocompromised patients. Information on the geographic range of an organism should be taken as a rough guide. The precise ranges of many pathogens have not been completely determined. Organisms may also expand their range or be eradicated from areas where they were once abundant. In this table, “worldwide” indicates those organisms that are widespread and found on all major continents, although they may absent from some areas (eg, polar regions or some islands). In some cases, organisms indicated as being present on a continent may nevertheless have a limited distribution.


        Global Zoonoses a


        Causative Organism

        Animals Involved

        Known Distribution

        Probable Means of Spread to People

        Clinical Manifestations in People

        Bacterial Diseases

        Actinomycosis (see Actinomycosis)

        Actinomyces bovis and other species in animals may affect people, but most human infections are caused by commensals of people, especially Actinomyces israelii


        Worldwide; very rare in people

        Probably contact; actinomycosis usually disseminates from endogenous human flora

        Granulomas, abscesses, skin lesions; chronic bronchopneumonia; abdominal mass that may mimic a tumor; endocarditis; sepsis

        Anthrax (see Anthrax)

        Bacillus anthracis

        Mainly in cattle, sheep, goats, horses, wild herbivorous animals; virtually all mammals and some birds are susceptible to high dose

        Worldwide but distribution is focal; common in Africa, Asia, South America, Middle East, parts of Europe

        Occupational contact exposure (abraded skin, mechanical transmission by biting flies, other routes); ingestion/foodborne, rarely airborne

        Early signs vary with route of inoculation; papule to ulcerative skin lesions; mild to severe gastroenteritis ± hematemesis, bloody diarrhea, ascites (abdominal GI form); sore throat, dysphagia, fever, neck swelling, mouth lesions (oropharyngeal GI form); pneumonia; all may progress to sepsis, meningitis; untreated cases fatal in 5%–20% (cutaneous) to 100% (inhalation)

        Arcobacter infections

        Arcobacter butzleri, A cryaerophilus, A skirrowii, possibly others

        Poultry, cattle, pigs, sheep, horses, shellfish; some studies detected these organisms in dogs and/or cats


        Ingestion of contaminated water, undercooked meat (especially poultry) has been suggested

        Gastroenteritis; bacteremia, mainly in patients with chronic illnesses; endocarditis, peritonitis; emerging and incompletely understood

        Bordetella bronchiseptica

        Dogs, rabbits, cats, pigs, guinea pigs, other mammals

        Worldwide; uncommon in people

        Exposure to saliva or sputum, aerosols

        Sinusitis, bronchitis, pertussis-like illness; pneumonia and disseminated disease (eg, endocarditis, peritonitis, meningitis), usually in immunocompromised; wound infection

        Borreliosis (see Lyme Borreliosis)

        —Lyme disease

        Borrelia burgdorferi sensu lato complex (B burgdorferi sensu stricto, B garinii, B afzelii, B spielmanii, B japonica)

        Wild rodents, insectivores, hedgehogs, hares, other mammals; birds are reservoirs for agent; deer are hosts for tick vector only (blood meals)

        Agents exist worldwide where Ixodes ticks are found; human cases have been reported in North America, Europe, Australia, parts of Asia, Amazon region of South America

        Ixodes spp bites

        Nonspecific febrile illness early; target skin lesions in many; may progress to arthritis, neurologic, cardiac, and/ or skin signs (acrodermatitis chronica atrophicans); syndromes may vary with infecting agent

        —Tickborne relapsing fever

        B recurrentis, B crocidurae, B turicatae, B hermsii, B persica, B hispanica, others; some species such as B duttoni are human pathogens and not zoonotic

        Wild rodents, insectivores, possibly birds

        Africa, Asia, Europe, Americas; species varies with region

        Tick bites (mainly Ornithodoros spp)

        High fever, malaise, headache, myalgia, chills; neurologic signs or abortion possible; recurring episodes, often milder, after a symptom-free period; death in 2%–5%

        —Southern tick-associated rash illness

        Etiology uncertain; various Borrelia spp suggested

        USA; most cases in southeast

        Tick bite (Amblyomma americanum)

        Resembles Lyme disease

        Brucella abortus

        Cattle, bison, water buffalo, African buffalo, elk, deer, sheep, goats, camels, South American camelids; other mammalian spillover hosts

        Once worldwide, now eradicated from domestic animals in some countries or regions; reservoirs in wildlife in some disease-free areas

        Ingestion (especially unpasteurized dairy products or undercooked meat), contact with mucous membranes and broken skin; strain 19 vaccine

        Extremely variable, subacute and undulant to sepsis; often nonspecific febrile illness with drenching sweats early; arthritis, spondylitis, epididymo-orchitis, endocarditis, neurologic, other syndromes if chronic; case fatality 5% in untreated

        B melitensis

        Goats, sheep, camels; other mammalian spillover hosts

        Asia, Africa, Middle East, Mexico, Central and South America, some parts of Europe

        Ingestion (including unpasteurized dairy products or undercooked meat), contact with mucous membranes and broken skin; Rev 1 vaccine

        As above; this species highly pathogenic for people

        B suis biovars 1–4; biovar 5 has not been reported in people

        Swine and wild pigs (biovars 1, 2, 3), European hares (biovar 2), reindeer and caribou (biovar 4); B suis also in some other mammals

        Biovars 1 and 3 worldwide in swine-raising regions except eradicated or nearly eradicated from domestic pigs in some countries; biovar 2 in wild boar in Europe; biovar 4 in Arctic

        Ingestion, direct contact with mucous membranes and broken skin

        As above

        B canis

        Dogs; evidence of infection in wild canids including coyotes, foxes

        Worldwide; rare in people

        Probably via ingestion or contact with mucous membranes, broken skin; close contact, especially with animals that recently aborted or gave birth

        Probably as above

        B pinnipedialis and B ceti

        Marine mammals

        Atlantic, Arctic, and Pacific oceans; Mediterranean sea

        Laboratory exposure; sources of other infections unknown (possibly contact with animals or exposure to seawater); rare or underdiagnosed in people

        Few cases known: mild to severe febrile illness, similar to that caused by other Brucella spp; neurobrucellosis with headache and chronic neurologic signs; spinal osteomyelitis

        Campylobacter enteritis (see Enteric Campylobacteriosis)

        C jejuni, C coli, occasionally other species; some strains of C jejuni seem to have broader host ranges than others

        Poultry, cattle, swine, dogs, cats, rodents, other mammals, wild birds


        Foodborne (especially poultry and other meats, unpasteurized dairy products); waterborne; contact with infected animals (fecal/oral)

        Gastroenteritis from mild cases to fulminating or relapsing colitis; occasional sequelae such as reactive arthritis; occasionally, other syndromes, including sepsis

        Campylobacter fetus infection

        C fetus subsp fetus (most cases), C fetus subsp testudinum (proposed name); possibly C fetus subsp venerealis

        C fetus subsp fetus and C subsp venerealis in cattle, sheep, goats; C fetus subsp testudinum in reptiles


        Probably direct contact or ingestion; often unknown

        Opportunist; sepsis, meningitis, endocarditis, abscesses, other systemic infections in elderly, immunocompromised, or infants; abortions, preterm births in pregnant women, neonatal sepsis; gastroenteritis not prominent in most cases

        Capnocytophaga infection

        C canimorsus, C cynodegmi

        Dogs, cats

        Probably worldwide

        Bites or scratches

        Fever, localized infections to bacteremia or sepsis, endocarditis, meningitis; often in immunocompromised or elderly

        Cat scratch disease

        Bartonella henselae; B clarridgeiae and other Bartonella species also implicated rarely in cat scratch disease or other conditions (eg, endocarditis)

        Cats and other felids; other Bartonella spp in canids, rodents, rabbits, other animals


        Often associated with scratches, bites, especially from cats; potential for other exposures to broken skin via saliva; exposure of conjunctiva

        Lymphadenopathy (may be absent in elderly), fever, malaise, skin lesions at inoculation site in immunocompetent, usually self-limiting with complications (eg, endocarditis, neuroretinitis, neurologic disease) uncommon; inoculation into eye results in conjunctivitis ± ocular granuloma and local lymphadenopathy; risk of bacteremia, disseminated disease, bacillary angiomatosis in immunosuppressed

        Chlamydiosis (see also Psittacosis below)

        Chlamydia ( Chlamydophila) abortus, C felis

        C abortus in sheep, goats, cattle, other mammals; C felis in cats

        C felis worldwide; C abortus in most sheep-raising areas but not Australia or New Zealand

        Contact with animals; C abortus probably contact with pregnant or aborting ruminants

        C abortus: abortions, septicemia; C felis suspected agent of keratoconjunctivitis, also implicated in other conditions (controversial)

        Clostridial diseases (see Clostridial Diseases)

        Clostridium difficile; some ribotypes found in animals have been implicated as potential zoonoses

        Ribotypes from some calves, pigs, dogs are identical to some ribotypes found in people


        Possible zoonosis; from contact or ingestion in contaminated meat; also from environment and contact with infected people

        Gastroenteritis, varying in severity from diarrhea to fulminant colitis, usually in conjunction with antibiotic use

        Clostridium perfringens, type A (most common), C, or D; environmental or endogenous source, with some potential for zoonotic transmission

        Domestic and wild animals, people


        Foodborne (usually type A); nonfood-associated intestinal infection; wound contaminant, usually environmental; may be endogenous in debilitated from GI or urogenital tract

        Foodborne gastroenteritis, usually brief, self-limited except in debilitated; nonfood-related intestinal infection with prolonged diarrhea, sometimes bloody, mainly in elderly after antibiotics; life-threatening necrotic enteritis, often in debilitated; gas gangrene, sepsis; necrotic enteritis, gas gangrene, sepsis are fatal if not treated

        Corynebacterium ulcerans and C pseudotuberculosis infections

        C ulcerans, C pseudotuberculosis

        C ulcerans in cattle, pigs, small ruminants, dogs, cats, ferrets, other domestic and wild animals; C pseudotuberculosis in sheep, goats, cattle, horses, camelids, other mammals

        Probably worldwide; uncommon in people but may be increasing

        Direct contact, consumption of unpasteurized milk products

        Acute upper respiratory illness with sinusitis, sore throat, tonsillitis, or more severe pharyngitis resembling diphtheria (pseudomembranous pharyngitis); cardiorespiratory complications possible; peritonitis; isolated skin infection; some cases serious or fatal

        Dermatophilosis (see Dermatophilosis)

        Dermatophilus congolensis

        Cattle, horses, deer, sheep, goats, other mammals

        Worldwide, especially in warmer regions

        Usually direct contact with lesions; mechanical transmission on arthropod vectors, fomites possible

        Pustular desquamative dermatitis, other skin lesions

        Enterohemorrhagic Escherichia coli infectionsb

        E coli O157:H7; also implicated are types O157:H, and members of serogroups O26, O103, O104, O111, O145, and others

        Especially cattle, sheep; also goats, bison, deer, pigs, other species of mammals, birds


        Ingestion of undercooked meat (especially ground beef), vegetables or water contaminated with feces; direct contact with feces or contaminated soil

        Diarrhea or hemorrhagic colitis; up to 15% of patients with hemorrhagic colitis progress to hemolytic uremic syndrome (HUS); case fatality rate for HUS is 3%–5%, higher in some populations (eg, 5%–10% in children, up to 50% in elderly)

        Erysipelothrix rhusiopathiae

        Swine, sheep, cattle, rodents, marine mammals; many other domestic and wild mammals and marsupials, birds (including poultry), reptiles, fish, mollusks, crustaceans


        Contact with animal products; via skin, usually after scratch or puncture wound; contaminated soil (survives for weeks to months)

        Localized cellulitis, usually self-limiting, often on hands; generalized skin lesions (uncommon); arthritis, often in finger joints near skin lesion; endocarditis (with high mortality, 38%); generalization with sepsis, other syndromes uncommon and often in immunocompromised

        Glanders (see Glanders)

        Burkholderia mallei

        Equids are reservoirs; felids, many other domesticated and wild mammals also susceptible

        Middle East, Asia, Africa and South America

        Contact with infected animals, tissues through broken skin, mucous membrane; ingestion; inhalation

        Mucous membrane or skin lesions; pneumonia and pulmonary abscess; sepsis; chronic abscesses, nodules, ulcers in many organs, weight loss, lymphadenopathy; case fatality rate varies with form, but >95% in untreated septicemia

        Helicobacter infection

        H pullorum, H suis, other species suspected as zoonoses

        Poultry (H pullorum), rodents (H pullorum and other species), pigs (H suis), dogs (H canis), many other mammals

        Uncertain; possibly ingestion of undercooked meat or direct contact

        Gastroenteritis or diarrhea, liver disease; bacteremia in immunosuppressed patients

        Mycobacterium leprae

        Armadillos; nonhuman primates (rare)

        Armadillos in parts of southern USA, Mexico, South America; nonhuman primates in Africa, possibly other locations; only human reservoirs in other areas

        Transmission of animal leprosy to people likely

        Various skin lesions, sensory nerve lesions and deficits, nasal mucosal lesions; mild, self-limiting to progressive destruction

        Leptospirosis (see Leptospirosis)

        Leptospira spp

        Domestic and wild animals; reservoir hosts include rodents, dogs, cattle, pigs, farmed red deer, others


        Occupational and recreational exposure, or exposure to rodent-contaminated material in urban locations; especially skin, mucous membrane contact with contaminated urine, infected fetuses, or reproductive fluids; water- and foodborne

        Asymptomatic to severe, sometimes biphasic; nonspecific febrile illness followed by aseptic meningitis or icteric form (especially liver, kidney, CNS involvement, hemorrhages possible); pulmonary hemorrhage and edema, other syndromes; uveitis can be sequela; case fatality rate varies with syndrome (uncommon in aseptic meningitis, 5%–15% in icteric form, 30%–60% in severe pulmonary form)

        Listeriosis (see Listeriosis)

        Listeria monocytogenes (types most often associated with disease are ½a, ½b, 4b), Listeria ivanovii (rare)

        Numerous mammals, birds, fish, crustaceans


        Foodborne, especially unpasteurized dairy products, raw meat and fish, vegetables, processed foods contaminated after processing; ingestion of contaminated water, soil; direct contact with infected animals; nosocomial in hospitals, institutions

        Acute, self-limited febrile gastroenteritis or mild, flu-like illness; ocular disease, conjunctivitis; abortion, premature or septicemic newborn if infected during pregnancy; meningitis, meningoencephalitis, septicemia in elderly, immunosuppressed, and infants; papular or pustular rash ± fever, chills in healthy adults after handling infected fetuses

        Melioidosis (Pseudoglanders, see Melioidosis)

        Burkholderia pseudomallei (other species of soil-associated Burkholderia, such as B oklahomensis sp nov in North America, rarely linked to human infections)

        Sheep, goats, swine; occasional cases in many other terrestrial and aquatic mammals; also reptiles, some birds including parrots, tropical fish

        Asia, Africa, Australia, South America, Middle East, Caribbean

        Wound infection, inhalation, and ingestion; organisms live in soil and surface water; most cases are acquired from environment, but direct transmission from animals is possible

        Mimics many other diseases; acute localized infections, including skin lesions, cellulitis, abscesses, corneal ulcers; pulmonary disease, septicemia, internal organ abscesses; often occurs in immunocompromised; case fatality rate varies with form, >90% in untreated septicemia

        Methicillin-resistant Staphylococcus aureus (MRSA) infections

        S aureus that carry mecA gene; some strains maintained in animals (eg, livestock-associated CC398), other strains mainly in people but animals can become carriers

        Pigs (major reservoirs for livestock-associated strain CC398, also carry ST9); cats, dogs mainly acquire strains from people; MRSA also reported in other mammals, including horses, cattle; birds, including poultry, psittacines; turtles

        Worldwide; can be reverse zoonosis or zoonosis; major strains in animals can vary with region

        Usually by direct contact (typically with asymptomatic carrier animals); other routes also described; can be nosocomial in hospitals

        Opportunist; localized skin and soft-tissue infections, invasive disease including septicemia, toxic shock syndrome; mortality varies with syndrome and success in finding antibiotic

        Mycobacterium avium complex

        Many species of mammals, some birds


        Environmental, mainly from water, and/or soil; infection common to people and animals

        Soft-tissue and bone infections; cervical lymphadenitis; pulmonary disease, often in immunocompromised or those with preexisting lung conditions; disseminated in immunocompromised, especially AIDS patients with uncontrolled disease

        M avium paratuberculosis

        Cattle, sheep, goats, camelids, deer, other ruminants; rabbits and other nonruminants; corvids


        Ingestion; accidental injection of vaccine

        Postulated involvement in Crohn’s disease after ingestion (controversial); severe local reaction if vaccine accidentally injected

        Mycobacteria other than tuberculosis (includes M simiae, M kansasii, M xenopi, M scrofulaceum, M szulgai, M chelonae, M marinum, M ulcerans, others)

        Cattle, other ruminants; swine, cats, dogs, koalas, other mammals, amphibians, reptiles (uncommon), fish; predominant Mycobacterium spp vary with host

        Worldwide; distribution varies with the organism

        Environmental, from water and/or soil

        Same syndromes as M avium complex; some organisms tend to be associated with certain syndromes (eg, M marinum, M ulcerans, with ulcerative or nodular dermatitis)

        Mycoplasma infections

        Mycoplasma spp

        Livestock, nonhuman primates, marine mammals, cats, dogs, rodents, other mammals

        Worldwide; zoonotic infections rare

        Direct contact; bites; wound contamination, including accidental inoculation

        Asymptomatic carriage; cellulitis; other syndromes, including respiratory disease, septic arthritis, septicemia have been reported, especially in immunocompromised

        Pasteurellosis (see Pasteurellosis of Sheep and Goats and see Pasteurellosis)

        Pasteurella multocida and other species

        Many species of domestic and wild animals, including dogs, cats, livestock, rabbits, birds


        Wounds, scratches, bites, close contact with mucus membranes

        Wound infections, cellulitis most common; other syndromes possible, including osteomyelitis, septic arthritis, sepsis, meningitis, respiratory disease; systemic conditions more common in immunocompromised

        Plague (see Plague)

        Yersinia pestis

        Rodents (eg, squirrels, prairie dogs, rats) and lagomorphs (pikas in Asia) are main reservoir; many mammals can be incidental hosts; cats and wild felids especially susceptible

        Foci in North and South America, Asia, Middle East, and Africa

        Flea bites, aerosols, handling infected animals or tissues (contact with broken skin or mucous membranes), bites or scratches, eating uncooked infected tissues

        Febrile flu-like syndrome with swollen, very painful draining lymph node(s) (buboes); pneumonia; sepsis can occur in either bubonic or pneumonic form; case fatality rate in untreated 40%–70% (bubonic) to 100% (pneumonic); <?5% mortality if bubonic form treated early

        Psittacosis and ornithosis (see Avian Chlamydiosis)

        Chlamydia (Chlamydophila) psittaci

        Psittacine birds (especially parakeets, cockatiels), pigeons, turkeys, ducks, geese, and other domestic or wild birds; mammalian strains of C psittaci also exist (zoonotic potential still undetermined)


        Inhalation of respiratory secretions or dried guano

        Influenza-like febrile illness with nonproductive cough that may progress to pneumonia; complications, including endocarditis, myocarditis, meningoencephalitis, hepatitis, glomerulonephritis, and other organ dysfunction; sepsis; some cases fatal if untreated, <1% with treatment

        Rat bite fever

        Streptobacillus moniliformis

        Rodents; might also be transmitted by carnivores (eg, dogs, cats, ferrets), which are probably infected or transiently colonized from rodents

        Probably worldwide

        Bites and scratches; handling or kissing a rodent, exposure to rodent urine; can be waterborne or foodborne

        Fever, severe myalgia and joint pain, headache, rash, sometimes GI signs; complications, including polyarthritis (usually but not always sterile), hepatitis, endocarditis, focal abscesses, sepsis possible if untreated; overall case fatality rate 10%–13% if untreated

        Spirillum minus

        Rodents; might also be transmitted by carnivores, which are probably infected or transiently colonized from rodents

        Organism is common only in Asia

        Mainly bites and scratches

        As above, but indurated, often ulcerated lesion at inoculation site; can relapse; some (minority) may have distinctive rash (large violaceous or reddish macules); polyarthritis is rare; overall case fatality rate 7%–10% if untreated

        Salmonellosis (see Salmonellosis)

        Salmonella enterica and S bongori (>?2,500 serovars)

        Widespread in mammals, birds, reptiles, amphibians, including domestic species; also in crustaceans; higher-risk pets for human exposure may include reptiles, amphibians, young poultry, some exotic mammals


        Foodborne infection or fecal-oral; some cases of occupational and recreational exposure

        Gastroenteritis to sepsis; focal infections possible; especially severe in the elderly, young children, or immunocompromised

        Streptococcal infections

        Streptococcus spp, including S suis, S equi zooepidemicus, S canis, S iniae, possibly others

        S suis in swine; S equi zooepidemicus in horses; S canis in dogs, cats; S iniae in fish; each species can also be found in other animals


        Ingestion, especially of unpasteurized dairy products, pork; direct contact often through broken skin; the human pathogen S pyogenes can also colonize bovine udder and be transmitted in milk

        Skin and soft-tissue infections; pharyngitis; other conditions, including pneumonia, meningitis, arthritis, endocarditis, streptococcal toxic shock syndrome, sepsis

        Tuberculosis (see also mycobacteriosis, above, see Tuberculosis and other Mycobacterial Infections, and see Tuberculosis)

        Mycobacterium bovis

        Cattle, bison, African buffalo, cervids, brushtail opossums, badgers, kudu can be reservoirs; swine and many other mammals can be spillover hosts

        Once worldwide, now eradicated or rare in some countries

        Ingestion (unpasteurized dairy products, undercooked meat including bushmeat), inhalation, contamination of breaks in the skin

        Skin lesions, cervical lymphadenitis (scrofula), pulmonary disease; genitourinary disease; can affect bones and joints, meninges; gastroenteritis

        Mycobacterium caprae

        Mainly goats, also infects other ruminants; can occur in other mammals, including pigs, horses, cervids, camels, carnivores

        Reported mainly in Europe

        Thought to be ingestion or direct contact with livestock, similarly to M bovis

        Extrapulmonary conditions, including skin lesions, meningitis, lymphadenitis, pericarditis, urinary, dissemination; also pulmonary disease

        Mycobacterium microti

        Rodents thought to be reservoir; can occur in domestic animals, including cats, dogs, ferrets, livestock

        Appears to be rare human zoonosis

        Most reported cases have been pulmonary; can also cause extrapulmonary disease

        Tularemia (see Tularemia)

        Francisella tularensis subsp tularensis more virulent, F tularensis subsp holarctica (F tularensis type B) less virulent, F tularensis subsp mediasiatica, F tularensis subsp novicida

        Rabbits, rodents, cats, sheep, other mammals, birds, reptiles, fish; often in wild animals

        F tularensis subsp tularensis almost exclusively in North America; F tularensis subsp holarctica in North America, Europe, Asia; F tularensis subsp mediasiatica in Central Asia; F tularensis subsp novicida reported in North America, Australia, Spain

        Contact with mucous membranes, broken skin; insect bites (tabanids, mosquitoes, hard ticks); fomites; ingestion in food or water; inhalation

        Nonspecific febrile illness, lymphadenitis; ulcerative skin lesions, exudative pharyngitis and stomatitis, conjunctivitis, gastroenteritis, respiratory signs or pneumonia, sepsis; case fatality rate 5% (localized disease, untreated) to >50% (untreated typhoidal form or severe respiratory disease)


        Vibrio parahaemolyticus

        Marine and estuarine shellfish, fish; also environmental in aquatic environments


        Ingestion; wound infections

        Gastroenteritis; dysentery (especially in some geographic regions); wound infections (mild to severe, including necrotizing fasciitis); sepsis; severe wound infections and sepsis usually in immunocompromised or those with liver disease (case fatality rate for sepsis 29%)

        V vulnificus

        Marine shellfish, crustaceans (eg, shrimp), fish; also environmental in aquatic environments

        Worldwide; human cases have been reported in North America, Europe, Asia

        Ingestion (often raw oysters); wound infection from water or handling hosts

        Wound infections from mild, self-limited lesions, bullae to cellulitis, myositis; necrotizing fasciitis; gastroenteritis; sepsis, usually in immunocompromised or those with liver disease, other debilitating illnesses; case fatality rate for sepsis >50%, and up to 25% for wound infections

        Vibriosis (continued)

        V cholerae O1/O139 (epidemic strains)

        Oysters, crabs, shrimp, mussels; most cases acquired from people

        Rare/absent to epidemic in different regions; one focus along USA Gulf Coast in shellfish


        Mild to severe, voluminous diarrhea, vomiting, dehydration; severe cases fatal if untreated, but low mortality if treated

        V cholerae non-O1/O139 (nonepidemic strains)

        Oysters, other seafood; also environmental in aquatic environments


        Ingestion; wound infection

        Gastroenteritis, usually mild and self-limited; wound infections; septicemia, usually in immunosuppressed or those with liver disease (case fatality rate for sepsis 47%–60% or higher)


        Yersinia pseudotuberculosis

        Many species of mammals, including swine, dogs, cats, rodents, wild mammals, birds

        Agent probably worldwide; prevalence may vary between regions

        Ingestion of contaminated water, food (including meat [especially pork], vegetables); fecal-oral (animal contact); dog bite (rare)

        Gastroenteritis (enterocolitis); pseudoappendicitis (with mesenteric lymphadenitis, terminal ileitis, fever, abdominal pain); severe GI bleeding possible in some cases of colitis; pharyngitis; sequelae may include erythema nodosum, reactive arthritis; sepsis, especially in elderly or immunocompromised

        Y enterocolitica; not all serotypes are pathogenic

        Many domestic and wild mammals, including rodents; some birds, reptiles, amphibians; zoonotic serotypes most common in pigs (major zoonotic source), pathogenic types also occur in dogs, cats

        Worldwide; prevalence of human disease may vary between regions (commonly reported in Europe)


        Gastroenteritis with watery diarrhea especially in young children, bloody feces uncommon; pseudoappendicitis; sequelae may include erythema nodosum, reactive arthritis; sepsis, other syndromes

        Rickettsial Diseases

        Human ewingii ehrlichiosis (formerly granulocytic ehrlichiosis)

        Ehrlichia ewingii

        Dogs, deer proposed

        Southeastern and south central USA; has been detected in South America

        Ticks, including Amblyomma americanum

        Few cases described; fever, headache, malaise, myalgia, nausea, vomiting; many patients were immunosuppressed

        Ehrlichia chaffeensis

        Deer are probably major reservoir in North America, dogs and other canids, lemurs, other mammals can also be infected

        North America; also reported in South America, Asia, and Africa

        Ticks, including Amblyomma americanum

        Asymptomatic to nonspecific febrile illness; rash in many pediatric cases, some adults; may progress to prolonged fever, renal failure, respiratory distress, hemorrhages, cardiomyopathy, neurologic signs, multiorgan failure; more severe in immunosuppressed, elderly; estimated case fatality rate 2%–3%

        Human granulocytic anaplasmosis (formerly human granulocytic ehrlichiosis)

        Anaplasma phagocytophilum (formerly Ehrlichia phagocytophilum and E equi)

        Wild rodents, deer may be reservoirs in North America; livestock, wild ungulates, wild rodents may be reservoirs in Europe; many other animals (eg, equids, ruminants, dogs, cats, birds) can also be infected


        Tick bites (Ixodes spp)

        Resembles human monocytic ehrlichiosis; often asymptomatic to mild in immunocompetent; rash uncommon; estimated case fatality rate <1%

        Infection by other Ehrlichia species

        E canis, E muris–like organism implicated rarely in human illness

        Dogs and other canids thought to be reservoirs for E canis, might also occur in felids; rodents may be reservoirs for E muris

        E canis worldwide; E muris Eastern Europe to Asia; E muris–like organism in North America

        Ticks (E canis transmitted by Rhipicephalus sanguineus, E muris by Haemaphysalis flava and Ixodes persulcatus complex)

        Rare cases of febrile illness, in both healthy and immunosuppressed

        Q fever (Query fever, see Coxiellosis)

        Coxiella burnetii

        Sheep, cattle, goats, cats, dogs, rodents, other mammals, birds, ticks


        Mainly airborne; exposure to placenta, birth tissues, animal excreta; occasionally ingestion (including unpasteurized milk); tickborne infections probably rare or nonexistent in people

        Febrile influenza-like illness; atypical pneumonia, hepatitis, endocarditis in some; possible pregnancy complications; overall case fatality rate 1%–2% if untreated

        Sennetsu fever

        Neorickettsia sennetsu

        Uncertain, possibly fish

        Japan, Malaysia, Laos, possibly other Asian countries

        Thought to be ingestion of raw fish

        Relatively mild, nonspecific, febrile illness, resembles infectious mononucleosis

        Spotted fever group of Rickettsia

        —African tick bite fever

        R africae


        Sub-Saharan Africa, eastern Caribbean

        Bite of infected tick (mainly Amblyomma hebraeum, A variegatum, also A lepidum, possibly Rhipicephalus decoloratus,Rhipicephalus appendiculatus)

        Nonspecific febrile illness; painful regional lymphadenopathy in many; eschars often multiple; nuchal myalgia; sometimes sparse maculopapular and/or vesicular rash; deaths do not seem to occur

        —Mediterranean spotted fever; Boutonneuse fever; Tick bite fever;

        R conorii subsp conorii

        Dogs, rabbits implicated as reservoirs; other animals can be infected

        Europe, especially Mediterranean; cases reported in sub-Saharan Africa

        Bite of infected ticks (mainly Rhipicephalus sanguineus, also others), crushing tick

        Nonspecific febrile illness; eschar (typically single) may or may not be present; rash, often maculopapular, in most; life-threatening disseminated disease or neurologic signs possible but uncommon; case fatality rate 1%–3% if untreated

        —Israeli spotted fever, Astrakhan spotted fever, Indian tick typhus

        R conorii subsp israelensis (Israeli spotted fever), R conorii subsp caspia (Astrakhan spotted fever), R conorii subsp indica (Indian tick typhus)

        Reservoir hosts uncertain

        Israeli spotted fever in Middle East, reported in Europe; Astrakhan spotted fever in Russia, Kazakhstan; Indian tick typhus in Asia (Indian subcontinent)

        Bite of infected ticks (mainly Rhipicephalus spp), crushing tick

        Astrakhan spotted fever and Indian tick typhus resemble Mediterranean spotted fever, but Israeli spotted fever may be more severe

        —Fleaborne spotted fever; Cat flea typhus

        R felis (synonym ELB agent)

        Unknown; dogs have been suggested as possible amplifying hosts

        North and South America, Europe, Asia, Africa, probably worldwide

        Flea bites; mainly associated with Ctenocephalides felis (cat flea), also infects C canis and other fleas

        Few clinical cases have been described but resembles other spotted fevers; febrile illness; rash in most; eschar may be uncommon; most cases seem to be mild but CNS involvement, pneumonia possible

        —Queensland tick typhus

        R australis

        Bandicoots, rodents


        Bite of infected Ixodes tick, especially I holocyclus, I tasmani

        Febrile illness, eschar may be present, rash (either maculopapular or vesicular) in most; mild in most, but serious disseminated disease, complications, death possible

        —Rickettsial pox

        R akari

        Mice; also rats, Korean voles

        Organism may be cosmopolitan; human cases seem to be uncommon

        Bite of infected rodent mites, Liponyssoides sanguineus

        Eschar (single) in most; febrile illness; maculopapular rash progresses to vesicular, pustular, resembles chickenpox; self-limiting

        —Rickettsia parkeri rickettsiosis

        R parkeri

        North America, detected in parts of South America

        Bite of infected ticks, Amblyomma maculatum; also found in other Amblyomma spp

        Resembles Rocky Mountain spotted fever (RMSF) but seems to be milder in most cases; differs from RMSF in that eschars occur in most cases (may be multiple), petechial rash does not seem to be characteristic

        —Rocky Mountain spotted fever (see Rocky Mountain Spotted Fever in Dogs)

        R rickettsii

        Rodents, rabbits, opossums, and other small mammals might amplify; dogs can be infected

        Western hemisphere

        Bite of infected ticks, especially Dermacentor variabilis, D andersoni (D variabilis in USA); Amblyomma cajennense, A aureolatum in South America; Rhipicephalus sanguineus in Arizona, Mexico, and South America; also from crushing tick

        Moderate to severe febrile illness; macular to generalized petechial rash; edema in some; usually no eschar; neurologic, pulmonary, hemorrhagic, and kidney signs in some; sepsis; gangrene; case fatality rate 15%–30% or higher (up to 85%) if untreated, ~3% or less with treatment in North America but higher in parts of Brazil

        —Tickborne lymphadenopathy; Dermacentor necrosis-erythema-lymphadenopathy

        R slovaca, R raoultii

        Uncertain; wild boar may be involved

        Europe to Central Asia

        Bites of infected ticks; R slovaca especially in Dermacentor marginatus, D reticulatus; R raoultii in Rhipicephalus pumilio, D nuttalli, other Dermacentor spp

        Eschar, local lymphadenopathy; localized alopecia at bite site; mild illness, fever and rash uncommon; no deaths reported

        —Other tickborne species in spotted fever group

        R sibirica, R japonica, R helvetica, R honei, R heilongjiangensis, R aeschlimannii, R massiliae, R monacensi, R amblyommii, others

        Various vertebrates

        Worldwide; distribution varies by species

        Bites of ixodid ticks; specific vector varies by species

        Inoculation site eschar (most); febrile illness with headache, myalgia, sometimes other signs; rash; local lymphadenopathy (some species); major signs, risk of complications, severity vary with species of Rickettsia

        Typhus group of Rickettsia

        —Murine typhus; Fleaborne typhus

        R typhi (formerly R mooseri)

        Rats are major reservoir; cats, opossums, possibly dogs, other species in peridomestic cycle

        Worldwide, especially warmer regions

        Infected rodent fleas, usually via flea feces; cat fleas seem to be involved in some cycles

        Fever, severe headache, central rash (not always observed); other signs, including arthralgia, cough, nausea/vomiting in some; mortality rate 4% without treatment

        —Scrub typhus; Chigger-borne rickettsiosis

        Orientia tsutsugamushi and related species

        Rodents, insectivores

        Asia, Australia, islands of southwestern Pacific Ocean; cases are usually concentrated regionally in “typhus islands”

        Bite of infected larval trombiculid mites (chiggers)

        Eschar in some; rash, headache, fever, painful lymphadenopathy, body aches, interstitial pneumonitis, GI signs; pneumonia, neurologic signs or cardiac complications in some; mild to severe; convalescence prolonged; case fatality rate up to 30%–50% if untreated


        R prowazekii

        Flying squirrels

        Eastern USA

        Squirrel lice or fleas suspected

        Nonspecific febrile illness, rash; GI signs in some; sepsis possible; appears to be somewhat milder than non-zoonotic typhus, which has a mortality rate of 20%–60% if untreated

        Fungal Diseases

        Aspergillosis; Allergic bronchopulmonary aspergillosis (see Aspergillosis)

        Aspergillus spp

        Birds and mammals


        Environmental exposure (decaying vegetation or grains); infection common to people and animals, insignificant as zoonosis

        Allergic respiratory signs, especially in people with certain respiratory conditions or immunodeficiencies; allergic sinusitis; pneumonia sometimes with dissemination in immunocompromised (can be fatal); chronic pulmonary disease ± aspergilloma (fungus ball); localized infections of other organs, tissues

        Blastomycosis (see Blastomycosis)

        Blastomyces dermatitidis

        Dogs, cats, horses, marine mammals, other mammals

        Distribution in environment uncertain; clinical cases focal; locally acquired cases reported in parts of North America, Africa, Middle East, India

        Environmental exposure, organism is most common in moist soil; infection common in people and animals; also reported rarely by animal exposure

        Acute to chronic pulmonary disease; skin or bone lesions; meningitis, other syndromes, disseminated disease possible; course mild to severe, some cases fatal

        Coccidioidomycosis (see Coccidioidomycosis)

        Coccidioides immitis, C posadasii

        Cattle, sheep, horses, llamas, dogs, many other mammals

        Especially southwestern USA, Mexico, Central and South America; in arid or semiarid foci; some cases might be acquired outside usual foci

        Principally environmental exposure (inhalation of arthrospores), including fungal cultures; infection common in people and animals, one unusual case reported after necropsy of horse with disseminated disease

        Self-limited, febrile, flu-like illness, sometimes with cough, chest pain in healthy host; serious, possibly life-threatening pulmonary disease or disseminated infection with cutaneous/subcutaneous lesions, persistent meningitis or osteomyelitis, especially in immunocompromised

        Cryptococcosis (see Cryptococcosis)

        Cryptococcus neoformans var grubii, C neoformans var neoformans, C gattii

        Birds including pigeons, psittacines (mainly grows in guano; temporary colonization of intestinal tract also possible); clinical cases in cats, other mammals


        Principally environmental exposure, especially pigeon nests for C neoformans, trees for C gattii; via inhalation or through the skin; infection common in people and animals, insignificant as zoonosis

        Respiratory signs, mild to severe, often self-limiting in healthy host but more likely to be severe in immunocompromised; dissemination with CNS disease, ocular signs, other syndromes, most often in immunocompromised; skin lesions, either localized from inoculation (uncommon) or from disseminated disease

        Histoplasmosis (see Histoplasmosis)

        Histoplasma capsulatum var capsulatum

        Dogs, cats, bats, cattle, sheep, horses, many other domestic and wild mammals, birds

        Worldwide; clinical cases often cluster in regional foci

        Principally environmental exposure, avian or bat feces encourage growth of organism; infection common in people and animals; insignificant as zoonosis

        Flu-like, febrile illness, usually self-limiting in healthy hosts; skin lesions; chronic pulmonary disease, usually with preexisting lung disease; dissemination in very young, elderly, immunocompromised

        H capsulatum var duboisii

        As above


        As above

        Usually skin and subcutaneous lesions, osteolytic bone lesions but can disseminate

        Malassezia infection

        Malassezia spp

        Dogs, cats, other animals


        Exposure to symptomatic animals; normal levels on skin not thought to be a significant risk

        Dermatitis; zoonotic strains might be implicated in fungemia in preterm neonates, other immunocompromised

        Ringworm (Dermatophytosis, see Dermatophytosis)

        Microsporum and Trichophyton spp

        Dogs, cats, hedgehogs, cattle, sheep, goats, horses, rodents, other mammals, birds, very rarely reptiles


        Direct skin/hair contact with infected animals, fomites

        Skin and hair lesions, usually pruritic; rare skin dissemination in immunocompromised

        Sporotrichosis (see Sporotrichosis)

        Sporothrix schenckii

        Cats, other mammals, birds

        Worldwide; epizootics in cats in South America

        Primarily environmental in vegetation, wood, soil; inoculation from environment in penetrating wounds (splinters, bites, pecks), skin contact with lesions, especially in cats; bites, scratches, other close contact implicated during feline epidemics; inhalation rare

        Papules, pustules, nodules, ulcerative skin lesions, may follow course of draining lymphatics; mucosa can be affected; extracutaneous involvement, especially bones, joints; disseminated disease (including meningitis) can be seen in immunocompromised; acute or chronic pulmonary disease resembling tuberculosis after inhalation, especially with underlying lung disease (rare)

        Parasitic Diseases—Protozoans

        Babesiosis (see Babesiosis)

        Babesia microti complex, B duncani (formerly WA-1), and other species

        Rodents, insectivores, lagomorphs, some other mammals; reservoirs uncertain for some species

        Babesia spp worldwide in wild animals, many agents not identified to species; human illness due to B microti complex reported in North America (most), Europe, Asia, Australia

        Bite of infected Ixodes ticks for B microti

        Many immunocompetent patients may have mild to moderate flu-like, febrile illness; mild to severe hemolytic anemia, especially severe in immunocompromised and elderly; respiratory, hepatic, renal, and other organ dysfunction; recurrent or chronic infection may develop; dual infection with B burgdorferi may worsen both diseases; death possible in severe cases

        B divergens

        Cattle; B divergens or closely related organism in farmed reindeer, wild cervids

        Europe, possibly North Africa; similar organisms might be present in North America; reported in Asia (China)

        Tick bites (Ixodes ricinus)

        Usually in splenectomized; acute, severe hemolysis; persistent high fever, headache, myalgia, abdominal pain, sometimes GI signs; shock and renal failure; cases progress rapidly; usually fatal if untreated; milder flu-like cases have been reported in immunocompetent patients

        B bovis; uncertain zoonosis; some historical cases were probably B divergens

        Cattle, water buffalo, African buffalo, possibly other species

        Africa, Asia, Central and South America, Mexico, Australia, parts of Europe

        Tick bites (Rhipicephalus microplus and R annulatus)


        Balantidium coli and related species

        Swine, rats, nonhuman primates, other animals


        Ingestion, especially of water contaminated with feces

        Asymptomatic to mucoid, bloody feces; intestinal hemorrhage and perforation possible; rare extraintestinal cases

        Chagas’ disease (American trypanosomiasis, see Chagas’ Disease)

        Trypanosoma cruzi

        Opossums, lagomorphs, rodents, armadillos, dogs, cats, other wild and domestic mammals

        Western hemisphere—southern USA, Mexico, Central and South America

        Fecal material of reduviid bug in family Triatomidae contaminates bite wounds, abrasions, or mucous membranes; ingestion in contaminated food

        Acute disease—erratic fever, adenopathy, headache, myalgia, hepatosplenomegaly, swelling at inoculation site and eyelid; myocarditis or encephalitis in some; worse in immunocompromised

        Chronic form (in 10%–30% of patients)—cardiomyopathy, megaesophagus, megacolon, other forms; reported annual mortality rate in chronic form 0.2%–19% (higher rates from studies that include only cardiac patients)

        Cryptosporidiosis (see Cryptosporidiosis)

        Cryptosporidium parvum, C canis, C felis, C meleagridis, C cuniculus, C viatorum, C muris, and other species (C hominis and likely some genotypes of C parvum are adapted mainly to people)

        Cattle and other ruminants, dogs, cats, rabbits, other domestic and wild mammals, birds, reptiles, fish


        Fecal-oral; ingestion of contaminated food and water; inhalation

        Self-limiting gastroenteritis in healthy; can be cholera-like and persistent in immunocompromised, with weight loss, wasting; cholecystitis; respiratory signs, pancreatitis, other syndromes mainly in immunosuppressed

        Giardiasis (see Giardiasis (Giardia))

        Giardia intestinalis, also known as G duodenalis (formerly G lamblia); only some genotypes seem to have zoonotic potential

        Many domestic and wild mammals, including dogs, cats, ruminants, aquatic mammals such as beavers


        Ingestion of water and less often food; direct fecal-oral (hands or fomites)

        Gastroenteritis, may be persistent


        —Visceral (Kalaazar; see Leishmaniosis)

        Leishmania infantum

        Wild canids and dogs are primary reservoirs, also in other mammals

        Asia, South America, Caribbean, Africa, the Middle East, Europe (Mediterranean spreading north), North America

        Bite of sand flies Phlebotomus and Lutzomyia spp

        Undulating fever, hepatosplenomegaly; some have cough, diarrhea, lymphadenopathy, weight loss, petechiae or hemorrhages on mucous membranes, nodular lesions or darkening of skin; pancytopenia; mild cases with only a few signs may resolve on their own, but most other cases fatal if untreated

        —Cutaneous and mucocutaneous

        L tropica complex (except L tropica, which is maintained in people), L braziliensis complex, L mexicana complex, others

        Dogs (L peruviana), rodents, various wild mammals act as reservoir hosts; other mammals can be infected

        Mediterranean, Asia, Africa, Middle East, Mexico to South America, Caribbean; localized focus in USA (Texas and Oklahoma)

        As above

        Papules to ulcers or nodules on skin ± mucous membranes; single or multiple lesions; localized or disseminated; may persist or recur; atypical forms in immunosuppressed; cutaneous form rarely fatal, mucocutaneous form can be disfiguring and may be fatal if pharynx affected

        Malaria of nonhuman primates

        Nonhuman primate–associated Plasmodium spp, P knowlesi, rarely P cynomolgi, others also potential zoonoses

        Old and New World monkeys, apes

        P knowlesi in Asia; other species exist in Central and South America, Asia, Africa

        Bite of anopheline mosquitoes

        Febrile episodes with chills; headache, myalgia, malaise, cough, nausea, vomiting, and other symptoms in some; cases range from mild, self-limiting to fatal (3% case fatality rate for P knowlesi)


        Microsporidia of Enterocytozoon bieneusi, Encephalitozoon cuniculi, E intestinalis, E hellem, others; both zoonotic and anthropnotic transmission reported for some agents

        Widespread in vertebrates, including primates, rabbits, rodents, dogs, cats, cattle, pigs, goats, birds, fish; also in invertebrates


        Fecal-oral; direct contact; ingestion of contaminated food or water; aerosols; possibly vector-transmitted

        Keratitis; acute diarrhea (traveler’s diarrhea); chronic diarrhea in immunocompromised; may disseminate to systemic disease with variable symptoms in immunocompromised

        Rhinosporidiosis (see Rhinosporidiosis)

        Rhinosporidium seeberi; some strains may be host specific

        Natural hosts thought to be fish and amphibians; also found in various mammals, including horses, cattle, mules, dogs, and cats; birds

        Worldwide, especially in tropics; endemic in South America, Asia, and Africa

        Environmental exposure, probably water

        Nasal and other mucous membrane masses and polyps (mainly nose, nasopharynx, eye); may cause obstruction; rare disseminated disease with osteolytic lesions or affecting viscera; rare skin and subcutaneous lesions

        Sarcocystosis (Sarcosporidiosis, see Sarcocystosis)

        Sarcocystis suihominis, also called S meischeriana

        People, nonhuman primates are definitive hosts; swine are intermediate host


        Ingestion of raw pork

        Gastroenteritis, usually mild, or asymptomatic

        S hominis, also called S fusiformis

        People, nonhuman primates are definitive hosts; cattle are intermediate host


        Ingestion of raw beef

        Gastroenteritis, usually mild or asymptomatic

        Sarcocystis spp; S nesbitti may be one cause

        People are intermediate host; species of Sarcocystis and definitive host(s) are often unknown; definitive host for S nesbitti thought to be snakes

        Worldwide; symptomatic cases mainly in Asia, probably because of distribution of definitive host

        Assumed to be ingestion of oocysts shed in feces of definitive host(s) or sporocysts

        Main syndrome is myositis, acute and self-limited to chronic, moderately severe; also cough, arthralgia, transient pruritic rashes, headache, malaise, lymphadenopathy in some

        Toxoplasmosis (see Toxoplasmosis)

        Toxoplasma gondii

        Felidae, including domestic cats, are definitive hosts; essentially all other mammals (including livestock) and birds thought to be susceptible as intermediate hosts


        Ingestion of oocysts shed in feces of infected cats (including contaminated soil, food, water) or ingestion of tissue cysts in undercooked meat or unpasteurized milk

        Lymphadenopathy or mild, febrile, flu-like syndrome or uveitis in immunocompetent, nonpregnant host; often severe in immunocompromised, with neurologic disease, chorioretinitis, myocarditis, pneumonitis, or disseminated disease; infection of fetus may result in CNS damage or generalized infection; abortions and stillbirths

        Trypanosomiasis (African sleeping sickness, see Trypanosomiasis)

        Trypanosoma brucei; T brucei rhodesiense is zoonotic; T brucei gambiense is primarily a human pathogen, although some animals (eg, pigs) can be infected and might serve as minor reservoirs

        T brucei rhodesiense reservoirs may include cattle, sheep, antelope, hyenas, lions, other wildlife, people; also isolated from other mammals

        Africa; common below the Sahara desert

        Bite of infected tsetse fly (Glossina spp)

        Painful chancre at bite site in some patients; intermittent fever, headache, adenopathy, rash, arthralgia; neurologic signs such as somnolence, seizures; cardiac complications possible; gambiense disease may last years; rhodesiense disease acute, may last weeks to months; both usually fatal without treatment

        Parasitic Diseases—Trematodes (Flukes)


        Clonorchis sinensis (Chinese liver fluke)

        Dogs, cats, swine, rats, other mammals are definitive hosts; fish (and snails) are intermediate hosts


        Ingestion of undercooked infected freshwater fish or shrimp containing encysted larvae

        Cholecystitis symptoms, indigestion, diarrhea, mild fever; chronic infections associated with cirrhosis, pancreatitis, or cholangiocarcinoma


        Dicrocoelium dendriticum, possibly D hospes (lancet flukes)

        Ruminants, especially sheep, goats, cattle, occasionally other domestic and wild mammals are definitive hosts; land snails (first) and ants (second) are intermediate hosts

        D dendriticum on all major continents (may be focal); D hospes in Africa south of Sahara desert

        Ingestion of infected ants

        Abdominal discomfort, flatulent indigestion; occasionally GI signs (diarrhea, constipation, vomiting, pain); weight loss, fatigue; biliary obstruction, cholangitis, hepatomegaly, or acute urticaria possible


        Echinostoma revolutum, E ilocanum, E hortense, and other Echinostoma spp; Echinochasmus japonicus and other members of Echinostomatidae can also be zoonotic

        Cats, dogs, rodents, pigs, other mammals; birds, including poultry, are definitive hosts; fish, shellfish, tadpoles, snails are intermediate hosts

        Most human cases in Asia, Western Pacific; this group of parasites is widely distributed, including Europe, Americas, Middle East

        Ingestion of undercooked fish, shellfish, snails, or amphibians (frogs)

        Abdominal discomfort; diarrhea, especially in heavy infestation; malnutrition, anemia, edema may occur, especially in children; intestinal perforation has been reported


        Fasciola hepatica

        Cattle, sheep, water buffalo, horses, rabbits, other herbivores are definitive hosts; snails are intermediate hosts

        Worldwide or nearly worldwide; previously thought to be mainly in temperate areas but may be more widely distributed

        Ingestion of contaminated greens, eg, watercress, or water that contains metacercariae

        Gastroenteritis, hepatomegaly, fever, urticaria possible acutely; biliary colic and obstructive jaundice in chronic cases; aberrant migration with extrahepatic signs (eg, pulmonary infiltrates, neurologic signs, lymphadenopathy, skin lesions or subcutaneous swelling) in some

        F gigantica

        Cattle, buffalo, goats, sheep, zebras, other mammals are definitive hosts; snails are intermediate hosts

        Thought to occur mainly in tropical areas: Africa, Asia, Middle East, and western Pacific

        As above

        Signs resemble fascioliasis caused by F hepatica


        Fasciolopsis buski

        Swine, people are definitive hosts; snails are intermediate hosts

        Asian pig-raising regions

        Ingestion of aquatic vegetables or contaminated drinking water containing metacercariae

        Often asymptomatic; gastroenteritis; intestinal bleeding, obstruction, or perforation possible; facial, abdominal, extremity edema may occur


        Gastrodiscoides hominis; uncertain whether people and swine carry the same strains

        Swine, people, nonhuman primates, rodents, other mammals are definitive hosts; snails are intermediate hosts

        Asia (including the Philippines), also reported in Africa, Volga delta in Russia

        Possibly ingestion of water or aquatic plants

        Mild diarrhea if high parasite burden


        Heterophyes spp, Haplorchis spp, other heterophids

        Cats, dogs, foxes, wolves, cattle, other mammals, fish-eating birds are definitive hosts (host varies with species of parasite); fish (and snails) are intermediate hosts

        Middle East (especially Nile delta), Turkey, Asia

        Ingestion of undercooked fish containing encysted larvae

        Diarrhea with mucus, colicky pain; heart or CNS involvement possible; severity of signs may vary with species


        Metagonimus yokogawai, M miyatai, M takahashii, and other Metagonimus spp

        Cats, dogs, rats, other fish-eating mammals, possibly birds are definitive hosts; fish (and snails) are intermediate hosts

        Human illness mainly in Asia, also reported in Siberia; parasites have been found in Europe

        Ingestion of undercooked freshwater fish containing encysted larvae

        Diarrhea with mucus, anorexia, mild epigastric pain or abdominal cramps; malabsorption, weight loss if high parasite burden


        Metorchis conjunctus, Canadian liver fluke

        Dogs, foxes and other canids, cats, raccoons, muskrats, mink, other fish-eating mammals are definitive hosts; fish (and snails) are intermediate hosts

        North America; human infection rare

        Ingestion of undercooked freshwater fish containing encysted larvae

        Fever, abdominal pain (mainly epigastric), anorexia during acute stage; effects of chronic infection uncertain


        Troglotrema salmincola (also called Nanophyetus salmincola)

        Raccoons, foxes, dogs, cats, skunks, and other fish-eating mammals and birds are definitive hosts; salmonid and some non-salmonid fish (and snails) are intermediate hosts

        North America along Pacific coast, Russia

        Ingestion of undercooked fish or roe

        Mild gastroenteritis


        Opisthorchis felineus (cat liver fluke)

        Cats, dogs, foxes, swine, seals, other fish-eating mammals are definitive hosts; fish (and snails) are intermediate hosts

        Europe, Kazakhstan, Russia, Ukraine

        Ingestion of undercooked freshwater fish containing encysted larvae

        Acute febrile illness with arthralgia, lymphadenopathy, skin rash; suppurative cholangitis and liver abscess in subacute, chronic stages; possible increased risk of cholangiocarcinoma

        O viverrini (small liver fluke); zoonotic transmission can occur, but people are important hosts

        People, dogs, cats, rats, pigs, fish-eating mammals are definitive hosts; fish and snails are intermediate hosts

        Southeast Asia

        Ingestion of undercooked freshwater fish containing encysted larvae

        Upper abdominal pain, diarrhea, fever, jaundice possible acutely; chronic infections with cirrhosis, pancreatitis, high incidence of cholangiocarcinoma

        Amphimerus pseudofelineus

        Various mammals, birds, reptiles are definitive hosts; fish suspected as intermediate hosts

        North and South America

        Undetermined but probably ingestion of undercooked fish

        Paragonimiasis (Lung fluke disease)

        Paragonimus westermani, P heterotremus, P africanus, P mexicanus, and other species

        Dogs, cats, swine, wild carnivores, opossums, and other mammals are definitive hosts; snails and freshwater crustaceans are intermediate hosts; wild boars, sheep, goats, rabbits, birds, other animals are paratenic hosts

        Flukes are worldwide (distribution varies with species); most human infections in Asia, Africa, tropical America

        Ingestion of undercooked, infected freshwater crustaceans (crabs, crayfish); metacercariae on contaminated hands, fomites after preparing crustaceans, or undercooked meat from paratenic hosts such as wild boars

        Chills, fever possible during migration to lungs; pulmonary disease resembling tuberculosis with cough, blood-tinged sputum; abdominal form with dull pain, tenderness, possibly diarrhea; less often, neurologic signs, migratory skin nodules, other organ-specific symptoms; predominant signs vary with species of fluke

        Schistosomiasis, intestinal and hepatic

        Schistosoma japonicum

        Many mammals, including cattle, water buffalo (important host in Asia), swine, dogs, cats, deer, horses, nonhuman primates, and rodents, are definitive hosts; snails are intermediate hosts


        Penetration of unbroken skin by cercariae from infected snails in water

        Acute disease can include urticarial rash, mild signs, isolated pulmonary signs, or Katayama syndrome (occurs especially after first infection; febrile illness, sometimes with cough, diarrhea, abdominal pain, hepatosplenomegaly, and/or rash/urticaria); apparent clinical recovery may be followed by chronic intestinal schistosomiasis with abdominal pain/discomfort, diarrhea ± blood; chronic hepatic schistosomiasis with hepatosplenomegaly followed by liver fibrosis, ascites, portal hypertension with hematemesis and/or melena, portocaval shunting with pulmonary signs; ectopic parasites can cause seizures, paralysis, meningoencephalitis; intestinal and hepatic lesions tend to progress rapidly; death can occur

        S mansoni

        People, nonhuman primates are major reservoir (definitive) hosts; also in rodents, insectivores, cattle, dogs; snails are intermediate hosts

        Africa, Middle East, South America, Caribbean

        Penetration of unbroken skin by cercariae from infected snails in water

        Acute disease in some; intestinal (most often) and/or hepatic schistosomiasis similar to S japonicum but not as rapidly progressive; glomerulonephritis a possible complication; ectopic CNS parasites tend to cause transverse myelitis; also causes genital schistosomiasis with reproductive problems; death can occur

        S mattheei; S bovis and S margrebowiei might also be zoonotic

        Definitive hosts are artiodactylid ruminants (cattle, sheep, goats, waterbuck, wildebeest, antelope, buffalo), also found in nonhuman primates; snails are intermediate hosts

        Southern Africa; seems to be rare in people, and some infections may have been misidentified

        Penetration of unbroken skin by cercariae from infected snails in water

        Suggested agent in intestinal and hepatic schistosomiasis

        S mekongi

        People are reservoir (definitive) hosts; also found in dogs, pigs; snails are intermediate hosts

        Southeast Asia

        Penetration of unbroken skin by cercariae from infected snails in water

        Acute disease absent or very rare; intestinal and hepatic schistosomiasis; death can occur

        S intercalatum, S guineensis

        Primarily people, rodents may also be definitive hosts; some other mammals, including nonhuman primates, susceptible to infection; snails are intermediate hosts


        Penetration of unbroken skin by cercariae from infected snails in water

        Intestinal schistosomiasis only, often mild or asymptomatic; occasionally bloody feces, diarrhea

        Schistosomiasis, urinary

        S haematobium

        People are main reservoir (definitive host); occasionally infects nonhuman primates, pigs, buffalo, sheep, rodents, or other mammals; snails are intermediate hosts

        Africa (including Madagascar, Mauritius), the Middle East

        Penetration of unbroken skin by cercariae from infected snails in water

        Acute disease in some; chronic disease—hematuria, dysuria, kidney failure; calcification of bladder wall, ureter, and bladder can lead to bladder cancer; ectopic CNS parasites tend to cause transverse myelitis; genital schistosomiasis; death can occur

        Swimmer’s itch (Cercarial dermatitis)

        Schistosome cercariae from Schistosoma spp (mammals); Gigantobilharzia, Trichobilharzia, and Austrobilharzia spp (birds)

        Birds, mammals are definitive hosts; snails are intermediate hosts


        Penetration of unbroken skin by cercariae from infected snails in fresh- and saltwater

        Self-limiting urticaria, pruritus, rash; fever, local lymph node swelling possible in some cases

        Parasitic Diseases—Cestodes (Tapeworms)


        Bertiella studeri, B mucronata

        Nonhuman primates are usual hosts; other mammals, including dogs, people can be infected

        Asia, South America, Africa; can occur in imported primates in other areas

        Ingestion of infected oribatid mites in food

        Most cases asymptomatic; abdominal pain, vomiting, diarrhea, constipation, weight loss

        Coenuriasis (Coenurosis)

        Taenia multiceps

        Definitive hosts are canids; intermediate hosts are sheep, other herbivores

        Worldwide in scattered foci; mainly reported from Europe, Asia

        Ingestion of tapeworm eggs in canine feces, may be via water, vegetables, soil

        Painless skin swelling; possible CNS involvement (signs of mass lesion in brain) or larva in eye

        T serialis

        Definitive hosts are canids; intermediate hosts are lagomorphs, rodents, occasionally other mammals

        Africa, Europe, North America, Australia; rare in people

        As above

        Painless skin swelling; also in muscles and retroperitoneally; CNS involvement possible

        T brauni

        Definitive hosts are canids; intermediate hosts are gerbils, wild rodents, also people


        As above

        Most often in subcutaneous tissues (skin swelling) or eye, also CNS


        Taenia solium (see also Taeniasis)

        People are definitive hosts; swine, other mammals are intermediate hosts (people can be both definitive and intermediate hosts)

        Worldwide where swine are reared; most cases seen in Africa, Asia, Central and South America

        Ingestion of eggs (including autoinfection from adult parasite in human intestine)

        Inflammation in CNS caused by death of small larva or growth to large size (often years after infection); can cause seizures, other CNS signs; less often in eye or heart; massive numbers in muscles can also be symptomatic

        T crassiceps

        Foxes, also other canids and carnivores, including dogs, are definitive hosts; rodents, insectivores, rabbits, occasionally other mammals are intermediate hosts

        North America, Europe, Asia, and other areas where foxes are present

        Ingestion of eggs

        Tissue invasion (mainly subcutaneous, muscle), ocular; one paravertebral pseudohematoma with local bleeding, one CNS larva; many but not all cases in immunocompromised

        Diphyllobothriasis (Fish tapeworm infection)

        Diphyllobothrium latum (Dibothriocephalus latus), D nihonkaiense, D pacificum, D dendriticum, and other Diphyllobothrium spp

        Dogs, bears, seals, sea lions, gulls, and other fish-eating mammals and birds are definitive hosts; freshwater or marine fish (and copepods) are intermediate hosts

        Worldwide; distribution of species varies

        Ingestion of undercooked infected fish

        Usually asymptomatic; may cause mild abdominal distress, diarrhea (chronic relapsing diarrhea possible in some cases)

        Dipylidiasis (Dog tapeworm infection)

        Dipylidium caninum

        Dogs, cats, wild canids, some other wild carnivores are definitive hosts; fleas are intermediate hosts

        Worldwide; uncommonly reported in people

        Ingestion of dog or cat fleas

        Usually in children; asymptomatic or mild abdominal distress, diarrhea; proglottids in feces resemble cucumber seeds


        Echinococcus granulosus sensu lato

        Dogs, other canids, hyenas are definitive hosts; sheep, goats, cattle, water buffalo, swine, camels, cervids, rodents, other mammals, or marsupials are intermediate or aberrant hosts; strains of parasite can be adapted to different intermediate hosts

        Worldwide, strains differ in distribution

        Ingestion of tapeworm eggs in food or water, to mouth on hands; eggs stick to fur and hands

        Cause space-occupying lesions of organs, especially lung, liver, also other organs, rarely CNS; cyst grows slowly, can cause death if untreated; rupture can cause allergic reactions, dissemination of cysts

        E multilocularis

        Foxes and other wild canids and felids are usual definitive hosts, but parasite can also mature in dogs, cats; intermediate hosts are usually rodents, insectivores, some other mammals

        North America (mainly Canada to north central USA), northern and central Eurasia

        Ingestion of tapeworm eggs in food or water, to mouth on hands; eggs stick to fur and hands

        Usually involves liver with mass lesions, occasionally lung or CNS; primary lesion can metastasize to many organs; without treatment, 70%–100% cases are fatal

        E oligarthrus

        Wild felids are definitive hosts, can mature in cats; agouti, pacas, spiny rats are intermediate hosts

        Central and South America; rare in people

        Ingestion of tapeworm eggs in food or water, to mouth on hands; eggs stick to fur and hands

        Has been seen in a variety of internal organs, eyes

        E vogeli

        Bush dogs are usual definitive host, can mature in other canids, including dogs; pacas, agouti, nutria, nonhuman primates, and other mammals can be intermediate hosts

        Central and South America

        Ingestion of tapeworm eggs in food or water, to mouth on hands; eggs stick to fur and hands

        Usually involves liver, may invade adjacent tissues; mortality high in advanced cases, even with treatment (22% in one study)


        Hymenolepis nana (dwarf tapeworm); most human infections probably transmitted from people, but zoonoses possible

        People, nonhuman primates, rodents are definitive hosts; insects, including fleas, flour beetles, cereal beetles are intermediate hosts


        Accidental ingestion of tapeworm eggs or infected insects; autoinfection possible

        Mainly in children; mild abdominal distress, decreased appetite, irritability are most common; weight loss, flatulence, diarrhea possible

        H diminuta (mouse tapeworm, rat tapeworm)

        Rats, mice are definitive hosts; insects, including fleas and cereal beetles are intermediate hosts


        Ingestion of infected insects in food

        Mild abdominal symptoms of short duration

        Inermicapsifer infection

        Inermicapsifer spp

        Rodents, people are definitive hosts in Africa; people may be exclusive host outside Africa

        Africa, southeast Asia, tropical America

        Probably ingestion of infected arthropods

        Mild abdominal symptoms, if any

        Raillietina infection

        R celebensis, R demerariensis; most Raillietina spp have not been reported in people

        Rodents, nonhuman primates are definitive hosts for R celebensis, R demerariensis; other species in birds, mammals; arthropods, including ants, are intermediate hosts

        R demerariensis in tropical America (human cases mainly Ecuador, Cuba, Guyana, Honduras); R celebensis in Asia, Australia, Africa

        Probably ingestion of infected arthropods in food

        Vague discomfort, many cases asymptomatic; gastroenteritis, possibly other signs; mainly in children


        Spirometra spp (pseudophyllidean tapeworms, second larval stage)

        Dogs, cats, wild canids and felids are definitive hosts; copepods are first intermediate host; fish, frogs, reptiles are second intermediate hosts; primates, pigs, weasels, rodents, insectivores, other mammals, birds are paratenic hosts

        Worldwide; human cases most common in Asia

        Ingestion of infected cyclops (in water) or undercooked intermediate or paratenic host; application of contaminated tissues to skin (eg, as poultice)

        Nodular, itchy skin lesions that can migrate; conjunctival and eyelid lesions; urticaria, painful edema; other organ involvement, including CNS, eye


        —Asian taeniasis

        Taenia asiatica (also called T taiwanensis, T saginata asiatica

        Domestic and wild pigs, occasionally cattle, goats, monkeys are intermediate hosts; people are definitive hosts


        Ingestion of undercooked animal products, usually visceral organs such as liver and lung

        Vague abdominal complaints and proglottid passage; anal pruritus; possible that ingestion of eggs may be followed by larval migration and disseminated disease (uncertain/controversial)

        —Beef tapeworm disease

        T saginata

        Cattle, water buffalo, llamas, reindeer, camels, other domestic and wild ruminants are intermediate hosts; people are definitive host


        Ingestion of undercooked meat containing larvae

        Mild abdominal discomfort and proglottid passage; gravid proglottids may travel to ectopic sites and cause symptoms; eggs do not cause disseminated disease

        —Pork tapeworm disease; cysticercosis and neurocysticercosis

        T solium

        People are definitive host; swine, occasionally other mammals, including people, are intermediate hosts

        Worldwide where swine are reared; most cases seen in Africa, Asia, Central and South America

        Ingestion of undercooked pork containing larvae causes taeniasis; ingestion of eggs (including autoinfection from adult worm in intestine) causes cysticercosis

        Adult stage in intestine (taeniasis) mild or asymptomatic; cysticercosis usually asymptomatic for years until cysticercus becomes large or death of small cysticerci result in inflammation in CNS (seizures, other CNS signs) or infrequently in eye or heart; massive numbers in muscles can also be symptomatic

        Parasitic Diseases—Nematodes (Roundworms)


        Angiostrongylus costaricensis, also called Parastrongylus costaricensis

        Cotton rats and other rodents are definitive hosts; slugs are intermediate hosts

        Mainly in Central and South America, Caribbean parasite has also been reported in North America

        Accidental ingestion of slugs or possibly plants contaminated by their secretions

        Acute abdominal angiostrongyliasis; severe pain resembles appendicitis, especially in children; rarely, more insidious disease with liver involvement; complications can include intestinal ischemia, perforation; fatalities possible

        Angiostrongylus cantonensis, also called Parastrongylus cantonensis

        Rodents (rats, including Rattus and Bandicota spp) are definitive hosts; snails, slugs are intermediate hosts; land planarians, crustaceans (crabs, shrimp, prawns), amphibians, fish, reptiles are paratenic hosts

        Originated in Asia, spread to many other regions, mainly tropics, including Americas, Caribbean, Middle East, Australia

        Ingestion of raw/undercooked intermediate or paratenic host (or accidental ingestion on vegetables); possibly ingestion of plants contaminated by secretions of intermediate host

        Eosinophilic meningitis or meningoencephalitis, spinal cord involvement; ocular involvement with decreased vision; transient abdominal pain, pruritus in some; most cases relatively mild and self-limiting, but some fatal


        Anisakis, Pseudoterranova, and Contracaecum spp

        Marine mammals (cetaceans and pinnipeds) and fish-eating birds are definitive hosts; fish, crustaceans, and cephalopod mollusks are intermediate or paratenic hosts

        Worldwide but many cases in northern Asia and western Europe

        Ingestion of undercooked marine fish, squid, octopus

        Gastroenteritis with upper quadrant pain; parasite usually in stomach; small-intestinal infections unusual but can occur; colon, esophagus rarely involved; oropharyngeal worm can cause hematemesis, cough; urticaria and other allergic signs after ingestion of live or dead worms


        Ascaris suum; potentially zoonotic (controversial)

        Pigs, also reported occasionally in other mammals, including nonhuman primates, sheep, cattle

        Worldwide, prevalence varies

        Ingestion of eggs from environment (shed in feces)

        Visceral larva migrans (respiratory signs, fever during larval migration); GI signs


        —Hepatic capillariasis

        Capillaria hepatica (also called Calodium hepaticum)

        Rodents major host, also in many other wild and domestic mammals

        Worldwide in scattered foci

        Ingestion of embryonated eggs in soil

        Acute or subacute hepatitis with marked eosinophilia; subclinical to fatal

        —Intestinal capillariasis

        C philippinensis (also called Paracapillaria philippinensis)

        Aquatic birds, people can be definitive hosts; freshwater fish are intermediate host

        Philippines, Thailand, also reported occasionally in other parts of Asia, Middle East, Cuba

        Ingestion of undercooked infected fish

        Enteropathy with protein loss and malabsorption; diarrhea, abdominal pain; weight loss can be severe; death possible

        —Pulmonary capillariasis

        C aerophila (also called Eucoleus aerophilus)

        Dogs, cats, other carnivores

        Worldwide; rare in people

        Accidental ingestion of infective eggs in soil or contaminated food

        Fever, cough, bronchospasm, bronchitis, dyspnea; can mimic bronchial carcinoma

        Dioctophymosis (Giant kidney worm infection)

        Dioctophyma renale

        Mink, dogs, and other carnivores are definitive hosts; annelids are intermediate hosts; frogs, fish are paratenic hosts

        Worldwide; rare in people

        Ingestion of infected fish, frog, or annelid

        Renal colic, hematuria, pyuria, ureteral obstruction, various kidney complications can be fatal; subcutaneous nodule

        Dracunculiasis (Guinea worm infection)

        Dracunculus medinensis; people are most important host but possible role for zoonotic transmission in some locations

        People, nonhuman primates are definitive hosts; infections have also been reported in animals, but parasite identification sometimes uncertain; domestic animals not thought to maintain parasite but possible exceptions (eg, dogs in Chad); copepods are intermediate hosts

        Asia (mainly Indian subcontinent) and Africa

        Ingestion of infected cyclops in water

        No symptoms until just before larviposition (~1 yr); papule to vesicular skin lesion to ulcer that opens in water to reveal worm; allergic reaction common at this time, and secondary infection may occur



        Dirofilaria immitis

        Dogs, cats, other mammals especially carnivores, mustelids, primates are definitive hosts (mainly patent in dogs and wild canids); mosquitoes are intermediate hosts


        Bite of infected mosquitoes

        Fever, cough acutely, larvae result in infarct or coin lesion in the lungs; often asymptomatic; rarely involves eye or other body sites

        D tenuis, D repens, rarely other species

        D tenuis in raccoons; D repens mainly patent in dogs and some wild canids (eg, foxes); also infects cats but not usually patent

        D tenuis in North America; D repens in Asia, Europe, Africa

        Bite of infected mosquitoes

        Subcutaneous nodule or submucosal swelling, some migratory and/or painful; subconjunctival (rarely intraocular); internal location (mainly lung but also brain, other organs) possible

        —Malayan filariasis

        Brugia malayi; subperiodic form is of uncertain origin, thought to be zoonotic or maintained in both animals and people; periodic form is exclusive to people

        Cats, wild felids, pangolins, other carnivores, nonhuman primates susceptible

        Asia; subperiodic form limited to peninsular Malaysia, Thailand, and parts of Indonesia, Vietnam, and the Philippines in swamp-forest environments

        Bite of infected mosquitoes, Mansonia spp mainly associated with subperiodic form

        Lymphatic filariasis: recurrent painful lymphadenitis, lymphangitis, often preceded by prodromal illness with malaise or urticaria; may progress to elephantiasis, usually of legs; hypersensitivity syndrome with cough, chest pain, asthmatic attacks especially at night

        Filariasis caused by other Brugia species

        Brugia spp other than B malayi, including B pahangi

        Various domestic and wild mammals, including dogs and cats, are definitive hosts

        Asia, Africa, Americas


        Occasional zoonotic infections (eg, cutaneous nodules, granuloma in lymph nodes)


        Gnathostoma spinigerum, G binucleatum, and some other Gnathostoma spp

        Dogs, cats, wild carnivores are definitive hosts (G doloresi and G hispidum in pigs and wild boars); copepods, freshwater fish, eels, frogs, snakes, chickens, snails, pigs are intermediate or paratenic hosts

        Worldwide; most human cases from Asia; emerging along Pacific coast of Mexico, Ecuador, Peru, Argentina

        Ingestion of undercooked fish, poultry, or other intermediate or paratenic host, drinking water contaminated with copepods containing larvae; handling meat that contains larvae

        Fever, malaise, gastroenteritis, urticaria, soon after ingestion; migratory skin lesions (intermittent swelling, often painful or pruritic, or linear erythematous lesions) after weeks to years; may involve viscera, eye, or CNS; CNS involvement can be fatal or result in permanent damage with reported case fatality rates of 7%–25%


        Gongylonema pulchrum

        Ruminants, domestic and wild swine, other mammals, birds are definitive hosts; coprophagous insects (eg, beetles, cockroaches) are intermediate hosts

        Worldwide; rare in people

        Ingestion of infected beetles, probably on vegetables; possible inhalation of small beetles

        Movement of parasite in submucosa of mouth is sensed; local irritation; pharyngitis, stomatitis possible

        Larva migrans, cutaneous (see alsognathostomiasis, above)

        Ancylostoma braziliense, A caninum, A ceylanicum, Uncinaria stenocephala

        Cats, dogs, wild carnivores are definitive hosts

        Worldwide; distribution varies with the species

        Contact with infective larvae that penetrate skin, usually via soil

        Itchy, serpiginous, migrating skin lesions; papules, nonspecific dermatitis, vesicles; wheezing, cough, and urticaria may occur; myositis or ocular lesions possible; eosinophilic enteritis after ingestion of A caninum; A ceylanicum can also become patent in intestine, causing GI signs, anemia

        Bunostomum phlebotomum


        Temperate regions

        As above

        As above

        Strongyloides stercoralis and other Strongyloides spp found in animals

        S stercoralis in dogs, cats, primates, including people; other species in swine, sheep, goats, cattle, horses, raccoons, and other domestic and wild mammals

        Worldwide, more common in tropics and subtropics

        Contact with infective larvae that penetrate skin, from soil or direct contact with feces; autoinfection possible with S stercoralis

        Larva currens (linear, serpiginous urticarial inflammation, often rapidly progressive); S stercoralis may also mature in intestine, causing enteritis and other signs (see below)

        Larva migrans, visceral (see alsoangiostrongyliasis and anisakiasis, above)

        Toxocara canis, T cati, possibly others

        Dogs and wild canids (T canis), cats and wild felids (T cati) are definitive hosts; many species can be paratenic hosts


        Ingestion of embryonated eggs shed in feces of dogs and cats; via soil, water, food, fomites

        Fever, wheezing cough, upper abdominal discomfort; other symptoms, including neurologic signs, skin rashes also possible; may wax and wane for months; eye involvement (ocular migrans) may resemble retinoblastoma

        Baylisascaris procyonis, possibly other species of Bayliscascaris

        Raccoons, kinkajous are definitive hosts; dogs can be definitive or intermediate host; many mammals (including people), marsupials, and birds are intermediate or paratenic hosts

        North America, Europe, Japan

        Accidental ingestion of embryonated eggs in soil, water, or fecal-contaminated material

        Nonspecific signs, including fever, lethargy; hepatomegaly, pneumonitis, parasitic meningoencephalitis (may be fatal in infants, young children), ocular disease; other syndromes, including cardiac disease

        Oesophagostomiasis, Ternidensiasis

        Oesophagostomum spp, Ternidens deminutus; zoonotic potential may vary with parasite species/strain and geographic area

        Primates, including people

        Parasites found in Africa, Asia, South America; human cases mainly reported in Africa

        Ingestion of infective larvae in soil, often in food or water

        Abdominal pain and one or more masses ± mild fever; intestinal obstruction or abscessation possible; multinodular form (less common) with abdominal pain, persistent diarrhea, weight loss; rarely ectopic in omentum, liver, or skin


        Onchocerca gutturosa, O cervicalis, O jakutensis, O dewittei japonica, O reticulata, O lupi, others

        Definitive hosts include cattle, horses, cervids, wild boars, dogs and other canids, camels, other species

        Distribution varies with species

        Probably transmitted by black flies (Diptera: Simuliidae), possibly other vectors

        Ocular disease, subcutaneous nodules


        Strongyloides stercoralis; most human infections thought to be from strains adapted to people; frequency of maturation of canine S stercoralis in people undetermined, thought to be rare

        S stercoralis in dogs, cats, foxes, primates, including people

        S stercoralis worldwide; more common in tropical and subtropical climates

        Contact with infective larvae that penetrate skin, in soil or direct contact with feces; autoinfection possible

        Frequently asymptomatic in healthy; possible larva currens (seelarva migrans, above); respiratory signs in some (cough to bronchopneumonia), especially in elderly, immunocompromised; abdominal pain, diarrhea, sometimes with periodic urticarial or maculopapular rash; disseminated strongyloidiasis, neurologic complications, septicemia, and death may occur in immunocompromised

        S fuelleborni

        Primates, including people

        Africa, Asia, and in captive primates in other areas

        As above

        Associated with abdominal pain, occasional diarrhea, not well studied

        Thelaziasis (Eyeworms)

        Thelazia callipaedia, T californiensis, possibly T rhodesii

        Definitive hosts are dogs and other canids, cats (T callipaedia); dogs, wild mammals, occasionally cats (T californiensis); flies are intermediate hosts

        T callipaedia in Asia, Europe; T californiensis in North America (western USA); rarely in people

        Flies release parasite larvae on conjunctiva

        Conjunctivitis; corneal scarring, opacity in chronic cases

        Trichinosis (Trichinellosis)

        Trichinella spiralis and subspecies, T nativa, T britovi, T nelsoni, T pseudospiralis, possibly others

        Main reservoir may be wild carnivores (foxes, badgers, wolves, lynx), omnivores (bears, boars); also in any mammal that eats (or is fed) meat, including domestic swine, rodents, cats, dogs, horses, marine mammals; also birds (T pseudospiralis); T zimbabwensis (zoonotic potential unknown) can infect reptiles

        Worldwide, especially in temperate regions; some species are limited in their distribution

        Ingestion of undercooked pork, horse meat, game, and other tissues containing viable cysts

        Gastroenteritis in some; followed by fever, headache, severe myalgia, facial swelling (especially eyelids); ocular pain, rashes, or pruritus possible; pneumonitis, CNS, or myocardial involvement can occur; inapparent to fatal


        Trichostrongylus spp

        Cattle, sheep, other domestic and wild ruminants, sometimes other mammals


        Ingestion of infective larvae on vegetables or in contaminated water, soil

        Asymptomatic or mild gastroenteritis

        Trichuriasis (Whipworm infection)

        Trichuris suis, possibly T vulpis and other species; main species in people is T trichiura, but zoonotic infections are unusual

        T vulpis in canids; T suis in domestic and wild swine

        Worldwide, especially warm, humid climates

        Ingestion of embryonated eggs on plant foods, water, or in soil

        T suis can colonize people, who develop GI signs; rare larva migrans or intestinal infections suggested from T vulpis (controversial identification)

        Parasitic Diseases—Acanthocephalans

        Acanthocephaliasis, Macracanthorhynchosis

        Macracanthorhynchus hirudinaceus and other species

        Hosts vary with parasite species; definitive hosts include domestic and wild pigs, rodents, muskrats, arctic foxes, dogs, sea otters, other terrestrial and marine mammals; intermediate hosts are beetles, cockroaches, crustaceans; fish are paratenic hosts


        Ingestion of infected beetles, other intermediate hosts, or fish

        Gastroenteritis, may lead to gut perforation or intestinal obstruction; some cases asymptomatic

        Parasitic Diseases—Annelids (Leeches)

        Hirudiniasis (internal)

        Limnatis nilotica and other aquatic leeches

        Cattle, buffalo, other domestic and wild mammals, probably frogs

        Africa, Asia, southern Europe, Middle East

        Drinking unfiltered water (leech enters nares or mouth), wading in deep water (enters genitourinary tract)

        Attaches to nasopharynx, pharynx, esophagus, occasionally deeper in respiratory tract, or in genitourinary tract; pressure and/or pain at attachment site; bleeding (eg, hemoptysis, hematemesis, epistaxis, vaginal bleeding), anemia (can be severe); other signs depend on location

        Arthropod Diseases

        Acariasis (Mange)

        Mites of Sarcoptes, Cheyletiella, Dermanyssus, and Ornithonyssus spp, Notoedres cati, Trixacarus caviae, Liponyssoides sanguineus; possibly others (uncommon)

        Mammals and birds


        Contact with infected animals, fomites

        Itchy skin lesions


        Cochliomyia hominivorax and Chrysomya bezziana (screwworms)

        Mammals; rare in birds

        C hominivorax in South America, Caribbean; C bezziana in Asia, Africa, Middle East

        Flies lay eggs on host, larvae enter wounds (as small as a tick bite), mucous membranes

        Painful, pruritic, foul-smelling, enlarging dermal and subdermal wounds or nodules, often with serosanguineous discharge; some infestations in cavities, including nasal cavity; larvae can invade living tissue, locally destructive (including bone, eye, sinuses, or cranial cavity); can be fatal if untreated

        Cordylobia anthropophaga, rarely C rodhaini (Tumbu flies)

        Mammals, often found in dogs, rodents

        Africa, Middle East; also reported in Mediterranean region of Europe

        Larvae from environment invade unbroken skin

        Furuncular swelling at site of invasion, often feet; fever, malaise, focal lymphadenopathy possible

        Cuterebra spp

        Rodents, lagomorphs, occasionally other mammals

        North America

        Larvae from vegetation enter host in natural cavities or invade intact skin

        Subcutaneous furunculoid nodule(s); creeping skin eruption (uncommon); ocular lesions; rarely larvae might be found in upper respiratory tract

        Dermatobia hominis(human botfly)

        Mammals, some birds

        South and Central America, Mexico

        Eggs carried by other insects (eg, mosquitoes); larvae hatch and penetrate skin of mammalian host when insect lands

        Nonmigratory larvae in furuncles; episodes of pain, intense pruritus, sometimes with lymphangitis or lymphadenitis; can invade eyelids, eye sockets, mouth, especially in children

        Gasterophilus spp (equine botfly)

        Equids, occasionally other mammals


        Accidental exposure to larvae

        Serpiginous, pruritic red stripes on skin resembling cutaneous larva migrans; very rarely might reach stomach (nausea, vomiting)

        Hypoderma lineatum, H bovis (warbles), and other Hypoderma spp

        H bovis and H lineatum in cattle, sometimes other mammals; other species primarily parasites of deer, caribou, or yaks

        North America, Europe, Asia; species distribution varies

        Eggs laid on host, larvae invade skin

        Usually subcutaneous (slowly moving furuncles that can appear and disappear) or similar to cutaneous larva migrans; endophthalmia uncommon; H lineatum may also cause an eosinophilic syndrome with fever, muscle pain, sometimes respiratory, cardiac, or neurologic signs

        Oestrus ovis, Rhinoestrus purpureus

        O ovis mainly in sheep, goats, also other mammals; R purpureus mainly in equids

        O ovis worldwide, usually in warmer climates; R purpureus in Asia, Africa, Europe

        Larvae are deposited in nares, conjunctiva, occasionally lips/mouth by adult fly

        Conjunctival form, with lacrimation and sensation of irritating foreign body in eye, ocular destruction rare; nasal form with localized pain or pruritus, congestion, headache; also reported in pharynx (inflammation, vomiting, dysphagia), rarely ear; usually self-limiting (except inside eye), because larvae cannot develop beyond first stage in people

        Wohlfahrtia spp, Wohlfahrtia vigil, W magnifica

        W vigil in rabbits, rodents, mink, foxes, dogs, and other carnivores, other mammals; W magnifica in sheep, cattle, dogs, other mammals, some birds, especially geese

        W vigil in North America; W magnifica in Europe (mainly Mediterranean), north Africa, Asia

        Larvae deposited on host or nearby, penetrate lesions (both agents) or intact skin (W vigil) and natural orifices

        W vigil causes subcutaneous abscesses, furuncles; W magnifica has been reported from skin, eye, vulva, ear, orotracheal region

        Pentastomid infections

        Armillifer spp (tongue worms)

        Definitive hosts are snakes; intermediate hosts are rodents and other wild animals

        Africa, Asia

        Ingestion, via water or vegetables contaminated with eggs (from feces or saliva of snakes); undercooked snake meat; contaminated hands, fomites after handling snake meat

        Usually asymptomatic; large numbers of parasites can cause multifocal abscesses, masses, or obstruction of ducts in internal organs; symptoms vary with location; death rare

        Linguatula serrata

        Definitive hosts are dogs and other canids, felids; intermediate hosts are herbivores (especially sheep, goats, lagomorphs) and people


        Ingestion of water or vegetables contaminated with eggs (from feces, saliva, or nasal discharge of definitive host); ingestion of larvae in undercooked liver or lymph nodes from intermediate hosts

        Ingestion of eggs—usually asymptomatic; ocular or pulmonary signs, abdominal pain, icterus, and other symptoms possible from invasion of internal organs

        Ingestion of larvae—throat irritation, pain; edema, congestion of nasopharynx may cause dyspnea, difficulty swallowing; most severe cases are probably in people who have been sensitized

        Tick paralysis (see Tick Paralysis)

        More than 40 species of ticks are capable of causing this disease; Dermacentor andersoni, D variabilis most common in North America

        Various animals carry ticks


        Tick attachment

        Ascending flaccid paralysis, may be preceded by prodromal flu-like illness (malaise, weakness); can cause respiratory paralysis, also paresthesia; ends when tick is removed

        Tunga infections

        Tunga penetrans(sand fleas, jiggers)

        People, dogs, pigs, other mammals

        Africa, Central and South America, Caribbean, south Asia

        Skin contact with contaminated soil

        Penetration of skin and burrowing result in pain and itching around discrete sores, often on feet; may be secondarily infected

        Viral Diseases

        Alkhurma virus infection

        Alkhurma virus (family Flaviviirdae, genus Flavivirus); may be a variant or strain of Kyasanur Forest virus

        Sheep, goats, camels

        Middle East, mainly reported in Saudi Arabia, also Egypt

        Ticks (Ornithodoros and Hyalomma spp); direct contact with animal meat via broken skin or ingestion of unpasteurized camel milk linked to some cases

        Febrile illness, often with GI signs (eg, vomiting, abdominal pain); encephalitic/neurologic and hemorrhagic signs in some; case fatality up to 25% in early reports, recently <1%

        Barmah Forest virus infection; epidemic polyarthritis

        Barmah Forest virus (family Togaviridae, genus Alphavirus)

        Natural hosts unknown; horses, brushtail possums may be hosts


        Mosquito bites; Culex annulirostris and Aedes spp implicated

        Resembles disease caused by Ross River virus (see entry later in this table) but seems to persist longterm in fewer patients, rash more common

        Buffalopox virus infection

        Vaccinia virus, Buffalopox virus strain (family Poxviridae, genus Orthopoxvirus)

        Water buffalo, cattle

        Indian subcontinent (south Asia), Egypt, Indonesia

        Skin contact with infected animals, often when milking

        Pox skin lesions mainly on hands, face, legs, buttocks; occasionally lymphadenopathy, fever, malaise

        California encephalitis virus serogroup (California serogroup) infections

        California encephalitis virus serogroup (family Bunyaviridae, genus Orthobunyavirus); includes California, La Crosse, Tahyna, Inkoo, Jamestown Canyon, Morro Bay, Snowshoe hare, Guaroa, Lumbo, Chatanga, and other viruses

        Many wild and domestic mammals

        North and South America, Europe, Africa, Asia; possibly worldwide; distribution of each virus varies

        Mosquito bites

        Syndromes, severity vary with the virus; flu-like illness, meningitis, or encephalitis common with North American viruses

        —La Crosse encephalitis

        La Crosse virus (California encephalitis virus serogroup)

        Chipmunks, squirrels are major amplifying hosts; rabbits, foxes, and other mammals can be infected

        North America

        Mosquito bites

        Many cases mild and flu-like; meningitis or encephalitis with seizures, paralysis, and focal neurologic signs possible; most cases in children; estimated case fatality rate <1% in cases with encephalitis

        —Tahyna fever

        Tahyna virus (California encephalitis virus serogroup)

        Hares, rabbits, rodents, hedgehogs, and other mammals

        Europe, Asia, Africa

        Mosquito bites (culicine and anopheles)

        Influenza-like illness, sometimes including GI signs; arthritis or respiratory signs, including bronchopneumonia in some; meningitis possible; most often in children; does not appear to cause fatal disease


        Camelpox virus

        Old World camelids, possibly other species

        Middle East, Asia, Africa, possibly other areas; human cases recently described in India in camel handlers, rare unconfirmed cases suggested in other locations

        Direct contact

        Skin lesions similar to cowpox, variola virus infections

        Chikungunya virus infection

        Chikungunya virus (family Togaviridae, genus Alphavirus)

        Sylvatic cycle in nonhuman primates, possibly rodents in Africa; virus thought to be maintained in people in Asia, but sylvatic cycle may also exist

        Asia, Africa

        Mosquito bites (especially Aedes spp)

        Febrile illness, may have rash and/or GI signs; arthralgia, especially in small joints, and myalgia prominent, may persist for months; myocarditis, neurologic signs, hemorrhages reported in a few cases

        Colorado tick fever

        Colorado tick fever virus (family Reoviridae, genus Coltivurus; Salmon River virus and California hare coltivirus may be variants

        Rodents; also found in porcupines, lagomorphs, deer, elk, and other mammals

        Rocky Mountain region of North America

        Tick bites (primary vector is Dermacentor andersoni)

        Nonspecific febrile illness; pharyngitis, rash, or GI signs possible; biphasic or triphasic in some; complications (eg, neurologic signs, hemorrhages, pericarditis, myocarditis, orchitis) uncommon but can occur in severe cases; deaths rare

        Contagious ecthyma (Orf, see Contagious Ecthyma)

        Orf virus (family Poxviridae, genus Parapoxvirus)

        Sheep, goats, camelids, reindeer, wild ungulates; rare cases in dogs


        Occupational exposure via contact with broken skin (both live animals and meat processing)

        Papule(s) that umbilicate and ulcerate, usually on hands; dissemination rare; large lesions refractory to treatment can be seen in immunosuppressed

        Cowpox (see Pox Diseases)

        Cowpox virus (family Poxviridae, genus Orthopoxvirus)

        Rodents are usual reservoir host; also in domestic and wild cats, occasionally cattle, other mammals

        Parts of Europe and Asia

        Contact exposure via broken skin, bites, scratches

        Papules, vesicles that become pustular, to ulcerative nodules, scars; single or multiple lesions, often on hands; regional adenopathy and malaise, flu-like symptoms in some; lesions remain localized in healthy people; more extensive or generalized disease may be seen in children, people with eczema,immunocompromised; severe cases can involve respiratory mucosa; rare fatal cases (eg, complications of encephalitis)

        Crimean-Congo hemorrhagic fever (see Crimean-Congo Hemorrhagic Fever)

        Crimean-Congo hemorrhagic fever virus (family Bunyaviridae, genus Nairovirus)

        Cattle, rodents, sheep, goats, hares, other mammals, some birds

        Africa, Middle East, central Asia, southeastern Europe; appears to be spreading

        Tick bites, especially Hyalomma but also Rhipicephalus, Dermacentor, other species; skin contact with animal or human blood or tissues or crushed ticks; ingestion of unpasteurized milk

        Fever, headache, pharyngitis, abdominal symptoms, petechial rash, hemorrhage, hepatitis, other organ involvement in some cases; very severe in pregnant women; case fatality rate 3%–50%, varies with region

        Eastern equine encephalomyelitis (see Equine Arboviral Encephalomyelitis)

        Eastern equine encephalomyelitis virus (family Togaviridae, genus Alphavirus); North American lineage 1 strains more virulent than South American lineages

        Birds are principal reservoir hosts in North America, snakes might have role in overwintering virus; rodents, marsupials might be reservoir hosts in South America; clinical cases seen in equids and occasionally other mammals and birds; mammals are almost always dead-end hosts

        Western hemisphere

        Mosquito bites; Culiseta melanura important in maintenance cycle in birds in North America; various mosquito species (Aedes, Coquillettidia, Culex) can transmit to people

        Nonspecific febrile illness may be followed by severe encephalitis, especially with North American lineage; neurologic sequelae common after encephalitis; case fatality rate 30%–70% with North American lineage; more severe in infants and elderly

        Ebola hemorrhagic fever

        Zaire ebolavirus, Sudan ebolavirus, Ivory Coast ebolavirus, Bundibugyo ebolavirus (family Filoviridae, genus Ebolavirus); Reston ebolavirus does not seem to affect people

        Bats are reservoir hosts for Zaire ebolavirus and suspected reservoir hosts for others; primates, duikers, possibly other mammals can be infected


        Contact with infected tissues (especially nonhuman primates and duikers); probable transmission from bats in caves

        Initially nonspecific febrile illness; maculopapular rash with desquamation; mild to severe bleeding tendency develops a few days after onset; mortality rate 36%–90%, varies with isolate


        Encephalomyocarditis virus (family Picornaviridae, genus Cardiovirus); thought to be zoonotic

        Rodents may be reservoir hosts; also in swine, nonhuman primates, elephants, other mammals, and wild birds

        Worldwide in animals


        Nonspecific febrile illness, sometimes with GI signs, and/or decreased reflexes have been reported in adults, with recovery within several days; CNS signs, including paralysis, have been reported in children

        Foot-and-mouth disease (see Foot-and-Mouth Disease)

        Foot-and-mouth disease virus (family Picornaviridae, genus Aphthovirus, types A, O, C, SAT 1, SAT 2, SAT 3, and Asia 1)

        Cattle, swine, sheep, goats, other cloven-hoofed animals (Artiodactyla), a few mammals in other orders

        Asia, Africa, Middle East, South America

        Contact exposure, often in laboratories or other high concentrations of virus

        People may become temporary nasal carriers of virus but do not usually become ill; mild influenza-like disease with vesicular lesions occurs very rarely

        Hantaviral diseases

        —Hantaviral pulmonary syndrome

        Sin Nombre, Black Creek Canal, Bayou, Andes, Bermejo, Choclo, Araraquara, Juquitiba, Laguna Negra, and Castelo dos Sonhosviruses, others (family Bunyaviridae, genus Hantavirus)

        Rodents; each virus tends to be associated with a single reservoir host

        North and South America

        Aerosols from rodent excretions and secretions; contact with broken skin and mucous membranes; rodent bites

        Prodromal stage with nonspecific febrile illness; followed by respiratory failure, cardiac abnormalities; hemorrhagic signs possible with South American viruses; significant kidney disease uncommon; mortality rate varies with the virus, but can reach 40%–60%

        —Hemorrhagic fever with renal syndrome

        Hantaan virus, Dobrava virus, Puumala virus, Seoul virus, Saaremaa virus, others (family Bunyaviridae, genus Hantavirus)

        Rodents; each virus tends to be associated with a single reservoir host, but Seoul virus is carried by both Rattus norvegicus and R rattus

        Europe, Asia; Seoul virus is worldwide

        Aerosols from rodent excretions and secretions; contact with broken skin and mucous membranes; rodent bites

        Prodromal stage with abrupt onset of fever, headache, back pain, sometimes petechiae, GI signs (may be severe); followed by hypotension, renal signs to renal failure with oliguria; hemorrhage, other syndromes in some; mortality rate varies with the virus, from <1% (Puumala virus) to 10%–15% (Hantaan virus)

        Hendra virus infection (see Hendra Virus Infection)

        Hendra virus (family Paramyxoviridae, genus Henipavirus)

        Fruit bats are normal reservoir host; horses can be infected


        Direct contact with infected animals (all human cases have been linked with horses) or contaminated tissues

        Respiratory infection, encephalitis (including recurrent encephalitis); few cases described but several were fatal

        Hepatitis E

        Hepatitis E virus, mammalian isolates (family Hepeviridae, genus Hepevirus); genotypes 3 and 4 zoonotic; genotypes 1 and 2 maintained in people

        People; animals, including swine, wild boar, deer, rabbits, ferrets, rats, mongoose, others; swine and probably other hosts are reservoirs for human infections

        Worldwide; human and zoonotic genotypes may differ in prevalence between areas

        Fecal-oral spread; consumption of raw or undercooked meat and liver; waterborne, contact with animal reservoirs

        Mild, self-limiting hepatitis to liver failure, more severe in pregnancy and can result in abortion, death of newborn, premature birth; usually acute, but can be chronic in organ-transplant patients; case fatality rate <1% to 4% in general population, up to 20% in pregnant

        Herpes B virus disease

        Cercopithecine herpesvirus 1 (McHV, Herpesvirus simiae, B virus) (family Herpesviridae, genus Simplexvirus)

        Carried in genus Macaca (Old World macaques), with lifelong latency and potential for periodic shedding after infection; other nonhuman primates susceptible; cell cultures

        Worldwide, can be common, especially in closed groups of macaques; human cases rare

        Monkey bites and scratches, contamination of mucous membranes with infected saliva, secretions

        Influenza-like symptoms; vesicular skin lesions, pain, or itching around wound, followed by severe encephalitis with seizures, paralysis, coma; 85% mortality rate

        Influenza virus infections

        —Avian influenza

        Influenza A virus (family Orthomyxoviridae, genus Influenzavirus A); avian influenza viruses; many severe human cases linked to Asian lineage H5N1 highly pathogenic avian influenza (HPAI) viruses, but other viruses also cause illness

        Avian influenza viruses in wild and domestic birds, especially poultry; uncommon in mammals

        Worldwide, distribution of strains varies

        Usually by contact with infected poultry; avian viruses may be shed in respiratory secretions and feces

        Avian influenza viruses can cause conjunctivitis, human influenza-like illness, or severe disease with multiorgan dysfunction, death; severity of disease varies with influenza strain

        —Swine influenza

        Influenza A virus (family Orthomyxoviridae, genus Influenzavirus A); swine influenza viruses

        Usually in pigs; also turkeys; can infect mink, ferrets


        Usually by contact with infected animals; swine influenza viruses occur in respiratory secretions

        Seems to resemble human influenza; severity of disease varies; fatal cases have been reported uncommonly

        Japanese encephalitis (Japanese B encephalitis)

        Japanese encephalitis virus (family Flaviviridae, genus Flavivirus)

        Swine, wild birds are important maintenance hosts; horses ill but epidemiologically unimportant in amplification; other mammals, reptiles, amphibians may be infected, usually asymptomatically

        Asia, Australia, Papua New Guinea, Pacific islands from Japan to the Philippines

        Mosquito bites (Culex tritaeniorhynchus) important in maintenance cycle, other Culex and Aedes spp can transmit); also through broken skin or mucous membranes after direct contact with infected tissues

        Fever, chills, myalgia, severe headache, GI symptoms; can progress to severe encephalitis; neurologic sequelae very common in survivors of encephalitis; case fatality rate 15%–30%

        Kyasanur Forest disease

        Kyasanur Forest virus (family Flaviviridae, genus Flavivirus)

        Rodents, shrews, other small mammals might be reservoirs (uncertain); affects monkeys; possible infections in other mammals, birds


        Tick bites (especially Haemaphysalis spinigera, also others)

        Nonspecific febrile illness; course may be biphasic; hemorrhagic signs (eg, ecchymoses, purpura, petechiae, GI bleeding, epistaxis) and/or neurologic signs possible in second stage; prolonged convalescence in many; case fatality rate ~3%

        Lassa fever

        Lassa virus (family Arenaviridae, genus Arenavirus)

        Wild rodents, usually multimammate mouse

        West Africa

        Contact with rodent excretions, secretions, or tissues; aerosols

        Gradual onset of nonspecific febrile illness, may be followed by chest pain, cough, GI signs, hepatitis; severe swelling of head and neck, hypotension/shock can develop; pleural/pericardial effusions; hemorrhagic syndrome less common; overall mortality rate 1% in endemic areas; case fatality rate 20% among hospitalized patients

        Louping ill (Ovine encephalomyelitis, see Louping Ill)

        Louping ill virus (family Flaviviridae, genus Flavivirus)

        Sheep, goats, also in llamas, cattle, horses, other domestic and wild mammals, grouse, ptarmigan

        UK, Northern Ireland; also reported in Norway, Spain; uncommon in people

        Tick bites (Ixodes ricinus); aerosol exposure in laboratory, contamination of skin wounds, contact with infected animals; possibly ingestion of milk

        Biphasic influenza-like illness, sometimes followed by meningitis or meningoencephalitis, paralysis, joint pain in second phase; not usually fatal

        Lymphocytic choriomeningitis

        Lymphocytic choriomeningitis virus (family Arenaviridae, genus Arenavirus)

        Reservoir mainly house mouse; can be maintained in some other mice, hamster populations; also infects guinea pigs, chinchillas, rats, nonhuman primates, some other mammals


        Contact with host excretions and secretions; bites; possibly ingestion

        Ranges from mild flu-like illness to biphasic with meningitis in second phase; complications (eg, arthritis, parotitis, orchitis) possible; can cause congenital defects (CNS defects, chorioretinitis, and other ocular lesions) or abortion; rarely fatal in immunocompetent (overall case fatality rate <1%)

        Marburg hemorrhagic fever

        Marburg virus (family Filoviridae, genus Marburgvirus)

        Bats are reservoir hosts; primates can be infected


        Contact with infected tissues (especially nonhuman primates); probable transmission from bats in caves

        Initially nonspecific febrile illness; maculopapular rash with desquamation; hepatitis; mild to severe bleeding tendency develops a few days after onset; mortality rate 20%–88%, varies with isolate

        Menangle virus infection

        Menangle virus (family Paramyxoviridae)

        Fruit bats are normal reservoir host; pigs can also be reservoir


        Close direct contact with tissues, amniotic fluid or blood of pigs reported in human cases

        Severe illness with fever, severe headache, myalgia, lymphadenopathy, drenching sweats, macular rash

        Middle East respiratory syndrome (MERS)

        MERS coronavirus

        Unknown reservoir host, possibly bats; source of infection for people uncertain, camels implicated

        Middle East

        Pneumonia, more likely in people with coexisting illness or immunosuppression but also in healthy; ~50% of known cases were fatal

        Milker’s nodules (Pseudocowpox, see Pseudocowpox)

        Pseudocowpox virus (family Poxviridae, genus Parapoxvirus)



        Skin contact (especially broken skin) with lesions on cow’s udder or mouth of calf; also from fomites

        Papular to nodular red skin lesions; self-limiting


        Monkeypox virus (family Poxviridae, genus Orthopoxvirus); Congo Basin clade causes more severe illness than West African clade

        Nonhuman primates, some wild and pet rodents, including Gambian rats, dormice, prairie dogs, African squirrels, some other mammals such as opossums; full host range uncertain

        West and central Africa

        Contact with lesions, blood or body fluids, fomites; bites; aerosols during close contact

        Smallpox-like disease; flu-like symptoms followed by maculopapular rash, which develops into vesicles, pustules, scabs; lymphadenopathy prominent; respiratory signs, encephalitis possible; case fatality rate varies with strain, <1% to 10%–17% or higher; milder in those vaccinated for smallpox

        Murray Valley encephalitis

        Murray Valley encephalitis virus (family Flaviviridae, genus Flavivirus)

        Wild water birds

        Australia, New Guinea

        Mosquito bites (Culex annulirostris)

        Asymptomatic or mild nonspecific febrile illness in majority; encephalitis, often with neurologic sequelae, or poliomyelitis-like flaccid paralysis in small number of patients; case fatality rate 15%–30% in encephalitic form

        Newcastle disease

        Newcastle disease virus/Avian paramyxovirus 1 (family Paramyxoviridae, genus Avulavirus)

        Domestic and wild birds

        Mildly virulent (lentogenic, mesogenic strains) are found worldwide; highly virulent (velogenic) strains found in Asia, the Middle East, Africa, Central and South America, parts of Mexico; also in cormorants in USA

        Occupational exposure, usually after contact with large amounts of virus

        Highly virulent (velogenic) strains can cause self-limiting conjunctivitis, possibly other syndromes

        New World hemorrhagic fever (Argentinean, Bolivian, Venezuelan and Brazilian hemorrhagic fevers [HF])

        Arenaviruses in Tacaribe complex (family Arenaviridae, genus Arenavirus): Juin virus (Argentine HF), Machupo virus (Bolivian HF), Guanarito virus (Venezuelan HF), Sabiá virus (Brazilian HF), Chapare virus; possibly others


        South America, related viruses might exist among rodents in Mexico

        Viruses found in rodent excretions, secretions, tissues; inhalation of aerosolized virus or direct contact with mucous membranes or broken skin

        Gradual onset of nonspecific signs, including myalgia, headache, and fever; may develop petechial or ecchymotic hemorrhages, bleeding, CNS signs, hypotension/shock; case fatality rate in untreated Bolivian hemorrhagic fever 5%–30%, untreated Argentine hemorrhagic fever 15%–30%

        Nipah virus infection (see Nipah Virus Infection)

        Nipah virus (family Paramyxoviridae, genus Henipavirus)

        Fruit bats are normal reservoir; swine can be reservoir; occasionally in other mammals (spillover hosts)

        Malaysia, Bangladesh, and Northern India; virus is probably endemic in southeast Asia, but outbreaks seem to cluster in certain geographic areas

        Direct contact with infected pigs or contaminated tissue; direct or indirect (eg, contaminated fruit juice) bat-to-human transmission

        Initial signs flu-like with fever, headache, myalgia, sometimes vomiting; encephalitis and meningitis; respiratory disease, including acute respiratory distress syndromes in some; septicemia; other complications in severely ill; case fatality rate 33%–75%

        Omsk hemorrhagic fever

        Omsk hemorrhagic fever virus (family Flaviviridae, genus Flavivirus)

        Voles, muskrats; also found in other animals


        Tick bites (Dermacentor spp); direct contact with body fluids or carcasses of muskrats and possibly other animal hosts

        Biphasic febrile illness with headache, GI signs, ± hemorrhages (nose, gums, lungs, uterus); CNS signs in minority of patients; mortality rate <3%

        Powassan virus encephalitis

        Powassan virus (family Flaviviridae, genus Flavivirus); two closely related lineages in different reservoirs

        Rodents (groundhog, squirrels, mice) and other small mammals thought to be reservoirs

        North America, eastern Russia

        Ixodes spp ticks, also found in Dermacentor andersoni

        Nonspecific febrile illness; may progress to neurologic signs, which may be severe; some cases fatal

        Rabies and rabies-related infections (see Rabies)

        Lyssaviruses:rabies virus (family Rhabdoviridae, genus Lyssavirus) and the related lyssaviruses, Duvenhage virus, Mokola virus, Australian bat lyssavirus, European bat lyssaviruses 1 and 2, Irkut virus, possibly others

        Wild and domestic canids, Mustelidae, Viverridae, Procyonidae, and order Chiroptera (bats) are important reservoir hosts; all mammals are susceptible; bats are reservoir hosts for Duvenhage virus, Australian bat lyssavirus, and European bat lyssaviruses; Mokola virus carried in rodents and shrews

        Rabies is worldwide with some exceptions: completely absent from some islands; countries also considered rabies-free if no cases in people or domestic animals for 2 yr; rabies-related lyssaviruses found only in Eastern Hemisphere (distribution varies)

        Bites of diseased animals; aerosols in closed environments

        Paresthesias or pain at bite site; nonspecific prodromal signs such as fever, myalgia, malaise; mood changes progress to paresthesias, paresis, seizures, and many other neurologic signs; survival in clinical cases thought to be very rare

        Rift Valley fever (see Rift Valley Fever)

        Rift Valley fever virus (family Bunyaviridae, genus Flavivirus)

        Sheep, goats, cattle, buffalo, African buffalo, camels, nonhuman primates; squirrels and other rodents; puppies and kittens

        Africa, foci on Arabian peninsula, Indian subcontinent

        Mosquito bites (Aedes spp and Culex triteniorynchus); contact with tissues

        Influenza-like febrile illness in most; complications, including hemorrhagic fever, meningoencephalitis in <5%; ocular disease in 1%–10%; other syndromes include acute renal failure or thrombosis; death uncommon except with hemorrhagic syndrome

        Ross River virus infection, Ross River fever; epidemic polyarthritis

        Ross River virus (family Togaviridae, genus Alphavirus)

        Marsupials, including wallaby, brushtail possum, might be natural hosts; dusky rat also proposed; people, horses, ruminants, pigs, rabbits, other mammals (minor hosts) may also be a source of virus during epidemics

        Australia, South Pacific Islands

        Mosquito bites (especially Culex annulirostris and Aedes spp)

        Mild fever, arthralgia ± arthritis, headache, rash; small joints most affected but large joints can also be involved; arthralgia, myalgia, lethargy may persist for months

        St. Louis encephalitis

        St. Louis encephalitis virus (family Flaviviridae, genus Flavivirus)

        Wild birds, domestic fowl; rodents, bats, other mammals might also maintain viruses in South America

        Western hemisphere

        Mosquito bites (Culex tarsalis, C pipiens-quinquefasciatus complex, C nigripalpus, also reported in other genera)

        Flu-like illness sometimes followed by meningitis or encephalitis, focal neurologic signs, dysuria; more severe in elderly and those with debilitating diseases; case fatality rate of 5%–20% reported in epidemics

        Severe acute respiratory syndrome (SARS)

        SARS coronavirus (family Coronaviridae, genus Coronavirus)

        Bats are thought to be reservoir hosts; can also infect palm civets, raccoon dogs, cats, pigs, ferrets, rodents, nonhuman primates, other mammals

        China, southeast Asia

        Contamination of mucous membranes with respiratory droplets or virus on fomites; possibly aerosol transmission

        Fever, myalgia, headache, diarrhea, cough; viral pneumonia with rapid deterioration; case fatality rate 15%

        Sindbis virus disease

        Sindbis virus (family Togaviridae, genus Alphavirus)

        Birds (passeriforms suspected as main reservoirs/amplifying hosts); occasionally found in other vertebrates

        Virus widespread in Eastern hemisphere; human cases tend to occur in limited geographic regions

        Mosquito bites; Culex and Culiseta, also others

        Fever, arthritis, rash, prominent myalgia; nausea, vomiting, mild jaundice in some; joint pain can persist for months; seems to be mild or asymptomatic in most children; no fatal cases reported


        Tanapox virus (family Poxviridae, genus Yatapoxvirus); Yaba-like disease virus may be a variant of tanapox virus

        Nonhuman primates

        Asia, Africa, and in monkey colonies

        Direct contact through broken skin; mosquitoes suspected to be vector in Africa

        Nonspecific febrile illness and papulovesicular or nodular lesions (lesions may be pruritic or tender), often on extremities; more than one or two skin lesions uncommon

        Tickborne encephalitis (Far eastern tickborne encephalitis, Russian spring-summer encephalitis, Central European tickborne encephalitis)

        Tickborne encephalitis virus (TBEV) (family Flaviviridae, genus Flavivirus); three subtypes: European (TBEV-Eu [least virulent]), Siberian (TBEV-Sib), Far Eastern (TBEV-FE)

        Small mammals especially rodents; also in goats, sheep, dogs, and other mammals; birds

        Eurasia; TBEV-Eu mainly Europe to former USSR; TBEV-FE mainly Asia to former USSR; TBEV-Sib mainly in Siberia

        Tick bites (mainly Ixodes ricinus and I persculatus; also other species); may be ingested in milk

        Often biphasic, with flu-like febrile illness in initial stage; neurologic signs from mild meningitis to severe encephalitis in some; myelitis or flaccid poliomyelitis-like paralysis (usually arms, shoulders, levator muscles of head); possibility of chronic and progressive forms, especially with TBEV-Sib; case fatality rate <2% (TBEV-Eu), 2%–3% (TBEV-Sib); case fatality rate 20%–30% in TBEV-FE may be based on severe cases

        Usutu virus infections

        Usutu virus (family Flaviviridae, genus Flavivirus)


        Africa, Europe

        Mosquito bites (Culex spp)

        Very few cases identified: fever with rash, fever with jaundice, or meningoencephalitis

        Vaccinia-related poxviruses

        Vaccinia or vaccinia-like viruses (family Poxviridae, genus Orthopoxvirus) of uncertain origin

        Reservoir uncertain; found in wild rodents, cattle, horses, nonhuman primates

        Appear to be endemic in Brazil

        Direct contact

        Pox skin lesions (papules, pustules, ulcerative nodules), may be accompanied by fever, lymphadenopathy

        Venezuelan equine encephalomyelitis

        Venezuelan equine encephalitis virus (family Togaviridae, genus Alphavirus)

        Enzootic subtypes maintained in rodents, other small mammals, bats; epizootic subtypes amplified in equids; occasionally in other mammals and birds

        Western hemisphere; enzootic strains Florida to South America; epizootic strains emerge in South America, spread

        Mosquito bites (Aedes, Culex, and Psorophora spp); exposure to aerosolized debris from infected laboratory rodents; laboratory accidents

        Most have nonspecific febrile illness, can be followed by neurologic signs; <5% children, <1% adults progress to encephalitis with case fatality rate of 10%–35% (highest rates in children <5 yr old)

        Vesicular stomatitis

        Vesicular stomatitis Indiana virus, vesicular stomatitis New Jersey virus, vesicular stomatitis Alagoas virus, and Cocal virus (family Rhadboviridae, genus Vesiculovirus)

        Swine, cattle, horses; occasionally in South American camelids, sheep, and goats; also rodents; serologic evidence of infection in many wild mammals, especially bats

        North and South America; most likely not endemic north of Mexico but sporadic outbreaks

        Contact with animals or in laboratory, probably also from insect bites, including mosquitoes and biting flies (Phlebotomus spp, Lutzomyia spp, and black flies)

        Usually asymptomatic; may develop acute, febrile, flu-like illness; vesicles can be found in mouth, pharynx, or inoculation site (eg, hands); self-limiting

        Wesselsbron fever

        Wesselsbron virus (family Flaviviridae, genus Flavivirus)

        Ruminants, especially sheep, goats; also evidence of infection in other mammals, including lemurs; can infect birds

        Southern Africa, southeast Asia

        Mosquito bites (mainly Aedes spp, possibly others); also by contact with contaminated material

        Nonspecific febrile illness ± maculopapular rash or ocular signs in some; few cases described but seems to be self-limiting

        West Nile fever and neuroinvasive disease (see Equine Arboviral Encephalomyelitis)

        West Nile virus (family Flaviviridae, genus Flavivirus); lineage 1 and lineage 2 viruses are both pathogenic

        Birds are primary reservoir hosts; also affects horses, other mammals, alligators, possibly other reptiles and amphibians

        Eastern and Western hemisphere

        Mosquito bites (primarily Culex univittatus, Culex spp); also by handling infected birds or reptiles or their tissues

        Nonspecific febrile illness, occasionally with rash; some cases progress to encephalitis, meningitis, and/or acute flaccid paralysis that resembles poliomyelitis; occasionally other syndromes; worse in elderly and immunocompromised; case fatality rate ~10% in all patients with neurologic disease, but higher in elderly

        Western equine encephalomyelitis (see Equine Arboviral Encephalomyelitis)

        Western equine encephalomyelitis virus (family Togaviridae, genus Alphavirus)

        Birds are reservoir hosts, may also cycle in jackrabbits, rodents; equids, other mammals are incidental hosts; virus also found in reptiles, amphibians


        Mosquito bites (Aedes, Culex, and Ochlerotatus spp); Culex tarsalis important in maintenance cycle in birds

        Nonspecific febrile illness may be followed by encephalitis in infants and children, uncommonly in adults; case fatality rate 3%–4%

        Yellow fever

        Yellow fever virus (family Flaviviridae, genus Flavivirus); only jungle cycle is zoonotic (people are reservoir for urban cycle)

        Nonhuman primates

        South America, Africa

        Mosquito bites (Haemagogus spp and Sabethes spp in jungle cycles in South America, Aedes spp in jungle cycles in Africa)

        Nonspecific, mild to severe febrile illness followed by liver and renal failure in some; hemorrhages (eg, epistaxis, hematemesis, melena, uterine hemorrhage) and often jaundice in severe cases; cases with hemorrhages often fatal

        Prion Disease

        Variant Creutzfeldt-Jakob disease

        Bovine spongiform encephalopathy prion

        Cattle are most important host; also infects other ruminants, cats and other felids, lemurs

        Most cases in the UK but also in many other countries

        Ingestion of bovine products, especially those contaminated with CNS tissues

        Neurodegenerative disorder similar to sporadic Creutzfeldt-Jakob disease but often in younger patients and progresses more rapidly; always fatal

        a Many proven zoonoses, including some relatively rare arthropodborne viral infections and helminth infections, have been omitted, as well as those diseases caused by fish and reptile toxins.

        b Enterotoxigenic, enteroinvasive, enteropathogenic, and enteroaggressive strains are not considered zoonotic.

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