Parasitic Diseases

Animals Involved
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

Known Distributions
Worldwide

Probable Means of Spreading
Ingestion of infected beetles, other intermediate hosts, or fish

Clinical Manifestations in People
Gastroenteritis, may lead to gut perforation or intestinal obstruction; some cases asymptomatic

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

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

Probable Means of Spreading
Accidental ingestion of slugs or possibly plants contaminated by their secretions

Clinical Manifestations in People
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

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

Known Distributions
Worldwide but many cases in northern Asia and western Europe

Probable Means of Spreading
Ingestion of undercooked marine fish, squid, octopus

Clinical Manifestations in People
Gastroenteritis with upper quadrant pain; parasite usually in stomach; small­intestinal 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

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

Known Distributions
Worldwide, prevalence varies

Probable Means of Spreading
Ingestion of eggs from environment (shed in feces)

Clinical Manifestations in People
Visceral larva migrans (respiratory signs, fever during larval migration); GI signs

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

Known Distributions
Asia

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

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

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

Known Distributions
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

Probable Means of Spreading
Bite of infected Ixodes ticks for B microti

Clinical Manifestations in People
Many immunocompetent patients may have mild to moderate flu­like, 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

Animals Involved
Swine, rats, nonhuman primates, other animals

Known Distributions
Worldwide

Probable Means of Spreading
Ingestion, especially of water contaminated with feces

Clinical Manifestations in People
Asymptomatic to mucoid, bloody feces; intestinal hemorrhage and perforation possible; rare extraintestinal cases

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

Known Distributions
Worldwide

Probable Means of Spreading
Ingestion of undercooked meat containing larvae

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

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

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

Probable Means of Spreading
Ingestion of infected oribatid mites in food

Clinical Manifestations in People
Most cases asymptomatic; abdominal pain, vomiting, diarrhea, constipation, weight loss

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

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

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

Clinical Manifestations in People
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)

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

Known Distributions
Asia

Probable Means of Spreading
Ingestion of undercooked infected freshwater fish or shrimp containing encysted larvae

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

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

Known Distributions
Worldwide in scattered foci; mainly reported from Europe, Asia

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

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

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

Known Distributions
Worldwide

Probable Means of Spreading
Fecal­oral; ingestion of contaminated food and water; inhalation

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

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

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

Probable Means of Spreading
Bite of sand flies Phlebotomus and Lutzomyia spp

Clinical Manifestations in People
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

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

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

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

Clinical Manifestations in People
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

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

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

Probable Means of Spreading
Ingestion of infected ants

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

Animals Involved
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

Known Distributions
Asia (mainly Indian subcontinent) and Africa

Probable Means of Spreading
Ingestion of infected cyclops in water

Clinical Manifestations in People
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

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

Known Distributions
Worldwide; distribution of species varies

Probable Means of Spreading
Ingestion of undercooked infected fish

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

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

Known Distributions
Worldwide; uncommonly reported in people

Probable Means of Spreading
Ingestion of dog or cat fleas

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

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

Known Distributions
Worldwide

Probable Means of Spreading
Bite of infected mosquitoes

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

Animals Involved
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

Known Distributions
Worldwide, strains differ in distribution

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

Clinical Manifestations in People
Cause space­occupying 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

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

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

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

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

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

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

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

Clinical Manifestations in People
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

Animals Involved
Swine, people are definitive hosts; snails are intermediate hosts

Known Distributions
Asian pig­raising regions

Probable Means of Spreading
Ingestion of aquatic vegetables or contaminated drinking water containing metacercariae

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

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

Known Distributions
Asia, Africa, Americas

Probable Means of Spreading
Mosquitoes

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

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

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

Probable Means of Spreading
Possibly ingestion of water or aquatic plants

Clinical Manifestations in People
Mild diarrhea if high parasite burden

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

Known Distributions
Worldwide

Probable Means of Spreading
Ingestion of water and less often food; direct fecal­oral (hands or fomites)

Clinical Manifestations in People
Gastroenteritis, may be persistent

Animals Involved
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

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

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

Clinical Manifestations in People
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%

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

Known Distributions
Worldwide; rare in people

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

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

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

Known Distributions
Worldwide in scattered foci

Probable Means of Spreading
Ingestion of embryonated eggs in soil

Clinical Manifestations in People
Acute or subacute hepatitis with marked eosinophilia; subclinical to fatal

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

Known Distributions
Middle East (especially Nile delta), Turkey, Asia

Probable Means of Spreading
Ingestion of undercooked fish containing encysted larvae

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

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

Known Distributions
Africa, Asia, southern Europe, Middle East

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

Clinical Manifestations in People
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

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

Known Distributions
Worldwide

Probable Means of Spreading
Accidental ingestion of tapeworm eggs or infected insects; autoinfection possible

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

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

Known Distributions
Africa, southeast Asia, tropical America

Probable Means of Spreading
Probably ingestion of infected arthropods

Clinical Manifestations in People
Mild abdominal symptoms, if any

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

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

Probable Means of Spreading
Ingestion of undercooked infected fish

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

Animals Involved
Cats, dogs, wild carnivores are definitive hosts

Known Distributions
Worldwide; distribution varies with the species

Probable Means of Spreading
Contact with infective larvae that penetrate skin, usually via soil

Clinical Manifestations in People
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

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

Known Distributions
Worldwide

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

Clinical Manifestations in People
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

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

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

Probable Means of Spreading
Bite of sand flies Phlebotomus and Lutzomyia spp

Clinical Manifestations in People
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

Animals Involved
Old and New World monkeys, apes

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

Probable Means of Spreading
Bite of anopheline mosquitoes

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

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

Known Distributions
Asia; subperiodic form limited to peninsular Malaysia, Thailand, and parts of Indonesia, Vietnam, and the Philippines in swamp­forest environments

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

Clinical Manifestations in People
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

Animals Involved
Cats, dogs, rats, other fish­eating mammals, possibly birds are definitive hosts; fish (and snails) are intermediate hosts

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

Probable Means of Spreading
Ingestion of undercooked freshwater fish containing encysted larvae

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

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

Known Distributions
North America; human infection rare

Probable Means of Spreading
Ingestion of undercooked freshwater fish containing encysted larvae

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

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

Known Distributions
Worldwide

Probable Means of Spreading
Fecal­oral; direct contact; ingestion of contaminated food or water; aerosols; possibly vector­transmitted

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

Animals Involved
Raccoons, foxes, dogs, cats, skunks, and other fish­eating mammals and birds are
definitive hosts; salmonid and some non­salmonid fish (and snails) are intermediate hosts

Known Distributions
North America along Pacific coast, Russia

Probable Means of Spreading
Ingestion of undercooked fish or roe

Clinical Manifestations in People
Mild gastroenteritis

Animals Involved
Primates, including people

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

Probable Means of Spreading
Ingestion of infective larvae in soil, often in food or water

Clinical Manifestations in People
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

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

Known Distributions
Distribution varies with species

Probable Means of Spreading
Probably transmitted by black flies (Diptera: Simuliidae), possibly other vectors

Clinical Manifestations in People
Ocular disease, subcutaneous nodules

Animals Involved
Cats, dogs, foxes, swine, seals, other fish­eating mammals are definitive hosts; fish (and snails) are intermediate hosts

Known Distributions
Europe, Kazakhstan, Russia, Ukraine

Probable Means of Spreading
Ingestion of undercooked freshwater fish containing encysted larvae

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

Animals Involved
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

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

Probable Means of Spreading
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

Clinical Manifestations in People
Chills, fever possible during migration to lungs; pulmonary disease resembling tuberculosis with cough, blood­tinged sputum; abdominal form with dull pain, tenderness, possibly diarrhea; less often, neurologic signs, migratory skin nodules, other organ­specific symptoms; predominant signs vary with species of fluke

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

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

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

Clinical Manifestations in People
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

Animals Involved
Dogs, cats, other carnivores

Known Distributions
Worldwide; rare in people

Probable Means of Spreading
Accidental ingestion of infective eggs in soil or contaminated food

Clinical Manifestations in People
Fever, cough, bronchospasm, bronchitis, dyspnea; can mimic bronchial carcinoma

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

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

Probable Means of Spreading
Probably ingestion of infected arthropods in food

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

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

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

Probable Means of Spreading
Environmental exposure, probably water

Clinical Manifestations in People
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

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

Known Distributions
Worldwide

Probable Means of Spreading
Ingestion of raw pork

Clinical Manifestations in People
Gastroenteritis, usually mild, or asymptomatic

Animals Involved
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

Known Distributions
Asia

Probable Means of Spreading
Penetration of unbroken skin by cercariae from infected snails in water

Clinical Manifestations in People
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

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

Known Distributions
Africa (including Madagascar, Mauritius), the Middle East

Probable Means of Spreading
Penetration of unbroken skin by cercariae from infected snails in water

Clinical Manifestations in People
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

Animals Involved
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

Known Distributions
Worldwide; human cases most common in Asia

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

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

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

Known Distributions
S stercoralis worldwide; more common in tropical and subtropical climates

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

Clinical Manifestations in People
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

Animals Involved
Birds, mammals are definitive hosts; snails are intermediate hosts

Known Distributions
Worldwide

Probable Means of Spreading
Penetration of unbroken skin by cercariae from infected snails in fresh­ and saltwater

Clinical Manifestations in People
Self­limiting urticaria, pruritus, rash; fever, local lymph node swelling possible in some cases

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

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

Probable Means of Spreading
Flies release parasite larvae on conjunctiva

Clinical Manifestations in People
Conjunctivitis; corneal scarring, opacity in chronic cases

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

Known Distributions
Worldwide

Probable Means of Spreading
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

Clinical Manifestations in People
Lymphadenopathy or mild, febrile, flu­like syndrome or uveitis in immunocompetent, non-pregnant 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

Animals Involved
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

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

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

Clinical Manifestations in People
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

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

Known Distributions
Worldwide

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

Clinical Manifestations in People
Asymptomatic or mild gastroenteritis

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

Known Distributions
Worldwide, especially warm, humid climates

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

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

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

Known Distributions
Africa; common below the Sahara desert

Probable Means of Spreading
Bite of infected tsetse fly (Glossina spp)

Clinical Manifestations in People
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