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Zoonotic Diseases: Parasitic Diseases

Zoonotic Diseases: Parasitic Diseases


Causative Organism

Animals Involved

Geographic Distribution

Probable Means of Transmission to Humans

Clinical Manifestations in Humans


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 are major hosts; can also infect reindeer, some sheep; closely related organism (B capreoli) in cervids

Europe, possibly North Africa

Tick bites (Ixodes ricinus)

Usually in splenectomized; acute, onset of severe hemolytic anemia; with persistent high fever, headache, myalgia, abdominal pain, sometimes GI signs; complications of respiratory distress and renal failure common; cases progress rapidly; usually fatal if untreated

B venatorum

Cervids are major hosts; also in sheep, probably other mammals

Europe, Asia

Tick bites

Resembles diseases due to other Babesia; noted in both healthy and immunocompromised


Balantidium coli and related species

Swine, rats, camels, ruminants, equids, nonhuman primates, other animals


Ingestion, especially of water contaminated with feces

Asymptomatic to watery or mucoid, bloody diarrhea; intestinal hemorrhage and perforation possible; rare extraintestinal cases at various sites including urinary tract, liver, lung

Trypanosoma cruzi

Many wild and domestic mammals including opossums, lagomorphs, rodents, armadillos, dogs, cats

Western hemisphere—southern US, California, Mexico, Central and South America

Fecal material of reduviid bug in family Triatomidae contaminates bite wounds, abrasions, or mucous membranes; ingestion in contaminated food; congenital infections possible and can lead to disease, often later in life

Acute disease—erratic fever, lymphadenopathy, 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; cardiac disease is associated with most deaths

Cryptosporidium parvum, occasionally C canis, C felis, C meleagridis, C cuniculus, C andersoni, C suis, C viatorum, C muris, and other species (C hominis and some C parvum are maintained in humans)

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

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 (eg, beavers)


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

Gastroenteritis, may be persistent

—Visceral (Kala-azar)

Leishmania infantum

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

South America, parts of Asia, the Middle East, Europe (mainly Mediterranean), North America (foxhound associated in this location)

Mainly bite of sand flies Phlebotomus and Lutzomyia spp, but also uncommon minor routes (eg, blood transfusion, transplacental, venereal)

Undulating fever, hepatosplenomegaly, nonspecific clinical signs (weight loss, malaise); some have other clinical signs such as cough, chronic diarrhea, lymphadenopathy, thrombocytopenia associated with petechiae or hemorrhages on mucous membranes, skin lesions, clinical signs of chronic kidney disease; pancytopenia; mild cases with only a few clinical signs (eg, localized lymphadenopathy) may resolve on their own; however, most other cases fatal if untreated

—Cutaneous and mucocutaneous

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

Diverse mammals and marsupials, primarily among wildlife, are reservoirs for the various species of Leishmania; other animals including domestic species can be infected;L peruviana has been detected in dogs but their relevance as a maintenance host uncertain

Leishmania occur on all major continents but distribution varies with the species and may be focal (most cases in Europe occur in the Mediterranean); North American infections are mainly associated with a localized focus of L mexicana in 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, especially in immunosuppressed; cutaneous form rarely fatal, mucocutaneous form can be disfiguring and may be fatal if pharynx affected

Malaria of nonhuman primates

P knowlesi, P cynomolgi, P simium, P brasilianum , others

Old and New World monkeys, apes

Southeast Asia, South America, 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; zoonotic importance may depend on genotype

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

Rhinosporidium seeberi; some strains may be host specific

Natural hosts thought to be fish and aquatic amphibians; various mammals and birds can be incidental hosts

Subtropical and tropical regions in South America, Asia, and Africa

Environmental exposure via water, especially stagnant 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 Sarcocystosis (Sarcosporidiosis)

Sarcocystis suihominis, S hominis, S heydorni

Humans are definitive hosts; swine are intermediate hosts for S suihominis; cattle are intermediate hosts for S hominis, S heydorni


Ingestion of parasites (sarcocysts) in raw tissues of intermediate host

Gastroenteritis, usually mild, or asymptomatic

Sarcocystis spp;a number of cases have been associated withS nesbitti

Humans are intermediate hosts for Sarcocystis spp, parasite often not identified to the species level; definitive host for S nesbitti thought to be snakes

Worldwide; most symptomatic cases are associated with S nesbitti and occur in Southeast Asia, especially Malaysia

Ingestion of oocysts or sporocysts shed in feces of definitive hosts, often in contaminated food or water

Main syndrome is myositis, which often ends in weeks to a few months, but may persist longer; some have nonspecific prodromal syndrome with fever, malaise, cough, arthralgia; transient pruritic rashes possible

Toxoplasma gondii

Felidae, including domestic cats, are definitive hosts; essentially all other mammals (including production animals) 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 ocular disease in immunocompetent, nonpregnant host, serious disease possible but uncommon; 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

T brucei rhodesiense;

Cattle, other domestic and wild animals are reservoirs

Sub-Saharan Africa

Bite of infected tsetse fly (Glossina spp)

Painful chancre at bite site in some patients; intermittent fever, headache, adenopathy, rash, arthralgia; neurologic signs; cardiac complications possible; usually fatal without treatment

Trematodes (Flukes)


Clonorchis sinensis (Chinese liver fluke)

Humans and carnivorous mammals are definitive hosts; snails and freshwater fish or shrimp are 1st and 2nd intermediate hosts


Ingestion of undercooked infected freshwater fish or shrimp containing encysted larvae

Nonspecific clinical signs, jaundice, hepatosplenomegaly,indigestion, chronic infections associated with cirrhosis, pancreatitis, or cholangiocarcinoma


Dicrocoelium dendriticum, possibly other species (eg, D hospes)

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 sub-Saharan Africa

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

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

Widely distributed, including Asia, Europe, Americas, Middle East, but most cases in humans reported in Asia, Western Pacific

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

Often subclinical; Abdominal discomfort; GI signs, especially in heavy infestation; malnutrition, may occur, especially in children


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 possibly acutely; biliary colic and obstructive jaundice in chronic cases; aberrant migration with extrahepatic signs possible

F gigantica

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

Thought to occur mainly in tropical and subtropical regions of Africa, Asia, Middle East, and western Pacific

As above

Clinical signs resemble fascioliasis due to F hepatica


Fasciolopsis buski

Swine, humans 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; heavy infection can be fatal


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

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

Asia, possibly other locations

Possibly ingestion of water or aquatic plants

Mild diarrhea if high parasite burden

Infection with heterophyid trematodes (Heterophyiasis, metagonimiasis)

Heterophyes spp, Haplorchis spp, Metagonimus spp, Centrocestus spp and other heterophyids

Diverse fish-eating mammals, 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, including accidental ingestion while preparing food

Diarrhea with mucus, colicky pain; involvement of extraintestinal sites (eg, heart or CNS) possible; severity of clinical signs may vary with species


Metorchis conjunctus (Canadian liver fluke) and other Metorchis spp

Various fish-eating domestic and wild mammals; birds are definitive hosts; fish (and snails) are intermediate hosts

M conjunctus in North America; other species in Asia, Europe

Ingestion of undercooked freshwater fish containing encysted larvae

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


Nanophyetus salmincola and other Nanophyetus spp

Various domestic and wild fish-eating mammals and birds are definitive hosts; salmonid and some non-salmonid fish (and snails) are intermediate hosts

North America and Eurasia along Pacific coast

Ingestion of undercooked fish or roe

Mild gastroenteritis


Opisthorchis felineus (cat liver fluke), O viverrini (small liver fluke)

Various fish-eating mammals including cats, dogs, pigs, wildlife, humans are definitive hosts; fish (and snails) are intermediate hosts

O felineus in Europe, Kazakhstan, Russia, Ukraine; O viverrini in Southeast Asia

Ingestion of undercooked freshwater fish containing encysted larvae

Initially asymptomatic or upper abdominal pain, GI signs, jaundice; acute febrile illness with arthralgia, lymphadenopathy, skin rash also reported; suppurative cholangitis and liver abscess in subacute, chronic stages; possible increased risk of cholangiocarcinoma

Amphimerus spp

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

North and South America (clinical cases mainly Ecuador); sporadic reports of Amphimerus spp in eastern hemisphere

Ingestion of undercooked fish

Asymptomatic or nonspecific clinical signs; possibly chronic effects similar to other liver flukes

Paragonimiasis (Lung fluke disease)

Paragonimus westermani, P kellicotti, 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 (eg, 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 clinical signs vary with species of fluke

Schistosomiasis, intestinal and hepatic

Schistosoma japonicum

Many wild and domestic mammals, including cattle, water buffalo, swine, dogs, cats, horses, and rodents are definitive hosts; snails are intermediate hosts


Penetration of unbroken skin by cercariae from infected snails in water

Acute disease in some with symptoms that may include fever, urticarial rash, nonspecific clinical signs, cough, hepatosplenomegaly, GI signs, apparent clinical recovery may be followed by chronic intestinal schistosomiasis with abdominal pain/discomfort, diarrhea ± blood; may induce inflammatory polyps in colon; chronic hepatic schistosomiasis with liver fibrosis, ascites, portal hypertension ectopic parasites can affect CNS; some cases fatal

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 humans, 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

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

Cestodes (Tapeworms)


Bertiella studeri, B mucronata

Nonhuman primates are usual hosts; other mammals, including dogs, humans 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, goats, other domestic and wild herbivores or omnivores, occasionally including humans; both domestic and sylvatic cycles exist

Appears cosmopolitan in scattered foci; however, domestic animal cycle no longer reported from some countries including US

Ingestion of eggs shed by canids in feces, may be via water, vegetables, soil

Various tissues but clinical cases most often reported in subcutaneous tissues, CNS, eye; large numbers of cysts in muscles can be symptomatic

T serialis (see also Taeniasis)

Definitive hosts are canids, primarily foxes; intermediate hosts are lagomorphs, infrequently rodents, occasionally other mammals including humans

Africa, Europe, North America, parts of Asia, Middle East, Australia, probably others

As above

As above

T brauni (T serialis brauni)

Definitive hosts are canids; intermediate hosts are wild rodents, occasionally other species including humans


As above

As above


Taenia solium

Definitive hosts are humans; Intermediate hosts are domestic and wild pigs, occasionally other mammals including humans

Cycle can be perpetuated where swine are reared and have access to human feces; most cases occur rural areas with poor sanitation in Africa, Asia, Central and South America; sporadic cases in developed countries including the US especially in foci where human carriers transmit eggs to other humans

Ingestion of eggs (including autoinfection from eggs shed by adult parasite in human intestine), may be in water, vegetables (or other food contaminated by human carriers), soil

Various tissues but clinical cases most often reported in subcutaneous tissues, CNS, eye; large numbers of cysts in muscles can be symptomatic. Disseminated cases affecting multiple organs are uncommon but can occur

T crassiceps, T martis,Hydatigera (Taenia) taeniaeformis, Versteria (Taenia) mustelae, probably others

Definitive hosts are carnivores and omnivores: T crassiceps mainly in canids, especially foxes; H taeniaformis most often in cats and other felids; T martis, V mustelae primarily in mustelids. Intermediate hosts for T crassiceps, H taenniaeformis, T martis, and V musteale are usually rodents and other small mammals; however, they occasionally infect other species including humans

Varies with the species. H taeniaformis is cosmopolitan; T crassiceps, T martis, and V mustelae occur in northern temperate zones (North America, Europe, Asia)

Ingestion of eggs shed in feces of definitive host, may be in water, vegetables, soil

As above. Most species form a single cysticercus from each larva but T crassiceps proliferates and can form large masses and spread to other sites

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 humans

Ingestion of dog or cat fleas

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

Echinococcosis (hydatid disease)

Echinococcus granulosus sensu lato complex: E granulosus sensu stricto, E canadensis, E ortleppiare known to be zoonotic

Dogs and other canids, hyaenids, occasionally felids are definitive hosts; sheep, goats, cattle, water buffalo, swine, camelids, equids, cervids, rodents, other mammals or marsupials are intermediate or aberrant hosts; Host specificity differs between species of Echinococcus

Worldwide, species 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; however, parasite can also mature in dogs, cats (cats mostly thought to play only minor role); intermediate hosts are usually rodents and other small mammals

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

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

Primary lesion usually in liver; primary lesion can metastasize to many organs; 90%–100% cases are fatal without treatment

E oligarthrus (= E oligartha)

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

Central and South America; rare in humans

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

Likely to affect internal organs, can occur in periorbital tissues

E vogeli

Bush dogs (Speothos venaticus) 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

Primary lesion usually involves liver, can spread to other sites; mortality high without treatment


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

Humans, 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, humans are definitive hosts in Africa; humans may be exclusive host outside Africa

Africa, southeast Asia, tropical America

Probably ingestion of infected arthropods

Mild abdominal symptoms, if any

Mesocestoides infection

Mesocestoides lineatus, M variabilis

Wild and domestic carnivorous mammals (canids, felids, procyonids, mustelids, others) are definitive hosts; Various mammals, birds, reptiles, amphibians are intermediate hosts; possibly 2nd invertebrate intermediate host

Possibly cosmopolitan but most clinical cases from Asia, North America


Asymptomatic cases probably most common; GI signs in some; motile proglottids observed

Raillietina infection

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

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

Definitive hosts are humans; Intermediate hosts are pigs and wild suids; cattle, goats and nonhuman primates were infected experimentally as intermediate hosts


Ingestion of mature cysticerci (larvae) in undercooked animal products, usually visceral organs, especially liver; however, some cysts have been found in muscle

Proglottid passage in feces but otherwise asymptomatic in many cases. Mild abdominal complaints (eg, discomfort, intermittent diarrhea, nausea, changes in appetite) in some. Rarely more serious syndromes, eg, obstruction or tapeworms at aberrant sites

—Beef tapeworm disease

T saginata

Definitive hosts are humans; intermediate hosts include cattle, water buffalo, reindeer, and other domestic and wild ungulates. Most species other than cattle have insignificant role in perpetuating cycle but reindeer play a role in northern Russia

Worldwide but typically uncommon in developed countries

Ingestion of mature cysticerci (larvae) in undercooked tissues, usually skeletal muscle (meat)

Proglottid passage in feces but otherwise asymptomatic in many cases. Mild abdominal complaints (eg, discomfort, intermittent diarrhea, nausea, changes in appetite) in some. Rarely more serious syndromes, eg, obstruction or tapeworms at aberrant sites T saginata proglottids are motile and can also migrate through anus, causing anal pruritus, and may occasionally travel to ectopic sites (eg, bile ducts, appendix) and cause symptoms

T solium

Definitive hosts are humans; Intermediate hosts are pigs and wild suids, occasionally other mammals including humans

Cycle can be perpetuated where swine are reared and have access to human feces; most cases occur in rural areas with poor sanitation in Africa, Asia, Central and South America; sporadic cases in developed countries including the US especially in foci where human carriers transmit eggs to other humans

Ingestion of mature cysticerci (larvae) in undercooked tissues, usually skeletal muscle (meat). Eggs shed by tapeworm carrier can be ingested by host or other humans, causing cysticercosis Cysticercosis Taenia multiceps multiceps is an intestinal parasite of canids (especially dogs, foxes, and jackals) and occasionally humans. Intermediate hosts include sheep, goats, deer, antelope,... read more

Proglottid passage in feces but otherwise asymptomatic in many cases. Mild abdominal complaints (eg, discomfort, intermittent diarrhea, nausea, changes in appetite) in some. Rarely more serious syndromes, eg, obstruction or tapeworms at aberrant sites. Some humans have concurrent cysticercosis.

Nematodes (Roundworms)


Angiostrongylus costaricensis, also called Parastrongylus costaricensis

Rodents are definitive hosts; patent infections reported occasionally in other mammals including dogs; 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 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 geographic areas, mainly tropics, including Americas, Caribbean, Middle East, Australia

Ingestion of raw or 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 location (uncommon) can cause hematemesis, cough; urticaria and other allergic signs after ingestion of live or dead worms


Ascaris suum

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; possibly eating contaminated undercooked tissues from infected animals

Acute or subacute hepatitis with marked eosinophilia; fever, diarrhea, respiratory signs also common; subclinical to fatal

—Intestinal capillariasis

C philippinensis (also called Paracapillaria philippinensis)

Aquatic birds, humans 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 canids and felids, other carnivores (eg, mustelids)

Worldwide; rare in humans

Accidental ingestion of infective eggs in soil or contaminated food

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

Dioctophymosis (Dioctophymiasis) (Giant kidney worm infection)

Dioctophyme (= Dioctophma) renale

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

Worldwide; rare in humans

Ingestion of infected fish, frog, or annelid

Renal colic, hematuria, pyuria, ureteral obstruction, various kidney complications can be fatal; aberrant locations include subcutaneous nodules, retroperitoneal

Dracunculiasis (Guinea worm infection)

Dracunculus medinensis; humans are most important host

Humans, nonhuman primates are definitive hosts; infections have also been reported in other animals; dogs appear to be reservoir hosts in some locations; copepods are intermediate hosts

Asia (mainly Indian subcontinent) and Africa

Ingestion of infected cyclops in water

No symptoms until just before larviposition (~1 year); 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; (mainly patent in dogs and wild canids; accidental hosts include primates (eg, humans, lemurs, pinnipeds)


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 repens, occasionally other species (eg, D tenuis, Dursi, D striata)

D repens mainly patent in dogs and some wild canids (eg, foxes); also felids (not usually patent), mustelids

Worldwide, distribution varies with the organism

Bite of infected mosquitoes

Subcutaneous nodule or submucosal swelling, some migratory 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 humans; periodic form is exclusive to humans

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 due to 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, conjunctival)


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; human cases; most common in areas where dietary risk factors common

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, possibly G nepalensis

Ruminants, domestic and wild swine, other mammals, birds are definitive hosts for Gongylonema spp; coprophagous insects (eg, beetles, cockroaches) are intermediate hosts; paratenic hosts might exist

Worldwide; rare in humans

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

Movement of parasite in submucosa of mouth is sensed; local irritation in oral cavity, esophagus, and pharynx; parasite in other locations (eg, eye) possible

Larva migrans, cutaneous (see also gnathostomiasis)

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 areas

As above

As above

Strongyloides stercoralis strains adapted to dogs and other Strongyloides spp found in animals

S stercoralis in dogs, cats, primates

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

Larva migrans, visceral (see also angiostrongyliasis and anisakiasis)

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 humans), 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 clinical 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 or strain and geographic area

Primates, including humans

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

Onchocercosis (Onchocerciasis)

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

Definitive hosts include various ungulates including cattle, horses, cervids, dogs and other canids

Distribution varies with species; some organisms (eg, O lupi widespread)

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 humans; frequency of maturation of canine S stercoralis in humans undetermined, thought to be rare

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

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; 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 humans

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 other species

Definitive hosts are dogs and other canids, cats, wild mammals; flies are intermediate hosts

T callipaedia in Asia, Europe, possibly other locations; T californiensis in North America (western US); rarely in humans

Flies release parasite larvae on conjunctiva

Conjunctivitis; corneal scarring, opacity in chronic cases

Trichinosis (Trichinellosis)

Trichinella spiralisT nativa, T britovi, T nelsoni, T pseudospiralis, 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 areas; 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; T trichiura (main species in humans) almost always acquired from other humans, zoonotic transmission possible but insignificant

T vulpis in canids; T suis in domestic and wild swine; T trichiura in nonhuman primates

Worldwide, especially warm, humid climates

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

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



Macracanthorhynchus hirudinaceus, Moniliformis moniliformis, Bolbosoma spp, Corynosoma stumosum and other species

Hosts vary with parasite species; definitive hosts include various domestic and wild mammals; intermediate hosts are beetles, cockroaches, crustaceans; fish, reptiles, amphibian can be paratenic hosts


Ingestion of infected beetles, other intermediate hosts, or fish

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

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


Acariasis (eg, Mmange)

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 or cattle grub)

Mammals (common in cattle in some regions), 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 or 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 humans

Wohlfahrtiamagnifica and other species

Various mammals, some birds

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

Larvae deposited on host or nearby, penetrate lesions or intact skin and natural orifices

Subcutaneous abscesses, furuncles; also reported from other sites including eye, genitourinary tract, ear, orotracheal region

Pentastomid infections

Armillifer spp (tongue worms)

Definitive hosts are snakes; intermediate hosts are rodents and other small mammals

Probably cosmopolitan; human cases reported in Africa, Asia, Europe, and North America

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 and may be nonspecific (eg, abdominal pain); ocular localization can result in blindness; death rare

Linguatula serrata

Definitive hosts are dogs and other canids, possibly felids; intermediate hosts are herbivores (eg, sheep, goats, lagomorphs) and humans


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

Ingestion of eggs is usually asymptomatic but ocular or pulmonary signs, abdominal pain, icterus, and other symptoms possible from larval invasion of internal organs; ingestion of larvae (nasopharyngeal linguatulosis) results in throat irritation, pain, possibly edema, congestion of nasopharynx dyspnea, difficulty swallowing; most severe cases of nasopharyngeal linguatulosis are probably in humans who have been sensitized

Tunga infections

Tunga penetrans(sand fleas, jiggers)

Humans, 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