CASES/YEAR
0 (US); 81,000,000 (Global)
OTHER NAMES
Bilharziasis; Snail fever; Schistosoma mansoni infection; Schistosoma japonicum infection;
INCUBATION
2-6 weeks for Katayama fever; [CCDM, p. 554] First eggs in stool 1-3 months after exposure; [Merck Manual, p. 1723]
INITIAL SYMPTOMS
Diarrhea, abdominal pain, and hepatosplenomegaly; Travelers to endemic areas may develop Katayama fever. [CCDM] "Swimmer's itch" is a pruritic papular rash that develops within 24 hours at the site of penetration. [PPID, p. 3454]
PRECAUTIONS
Not transmitted directly from person to person; [CCDM, p. 554]
COMMENTS
FINDINGS:
Cercarial dermatitis occurs within 24 hours of skin penetration and usually consists of papules at sites of entry on the lower legs. Acute schistosomiasis (Katayama fever) is flu-like illness that may occur 2-8 weeks after the first exposure (primary infection) in an endemic area, i.e., an illness of previously unexposed visitors. Findings in Katayama fever include urticaria, eosinophilia, leukocytosis, hepatosplenomegaly, lymphadenopathy, fever and sweats, cough, chest pain, dyspnea, and diffuse pulmonary infiltrates or nodules. Late in the illness, eggs appear in the stool. Intestinal infections can cause fatigue, diarrhea, and colicky abdominal pain, and may lead to anemia, strictures, and obstruction. Eggs deposited in the eye can cause choroiditis and optic neuritis. Repeated hematemesis from bleeding esophageal varices, as well as portal hypertension and splenomegaly are findings in chronic disease. Liver function is usually well maintained until late in the course, except in patients with alcoholism or viral hepatitis. CNS disease includes brain lesions and encephalitis. [Guerrant, p. 1015, 850-2; PPID, p. 3454-6] Chronic symptoms are caused by immune response to the schistosome eggs lodged in the blood vessels of the liver and intestine (S. mansoni and S. japonicum) or lodged in the urinary tract (S. haematobium). [CDC Travel, p. 312] Intestinal infection causes blood in the stools. Chronically infected and untreated patients die from bleeding or hepatic failure. [ID, p. 2378] Marked eosinophilia is present early. Eosinophilia may or may not be present during chronic infection. [Guerrant, p. 943] S. japonicum causes mass lesions of the CNS, and 1%-2% of infected patients have epilepsy. [Guerrant, p. 1018] Hepatic cirrhosis is a complication of infection by S. mansoni and S. japonicum. [Merck Manual, p. 1723] Neurological schistosomiasis is an uncommon complication with symptoms of delirium, seizures, visual and motor defects, myelitis, stupor, and coma. [Cohen, p. 1030] Bleeding esophageal varices occur in a small percentage of patients with cirrhosis. [Guerrant, p. 920]
EPIDEMIOLOGY:
Snails are intermediate hosts for these trematode infections. Humans, dogs, cats, pigs, cattle, water buffalo, and rodents can be hosts for S. japonicum. Human infections can last for more than 10 years, and other humans are infected in areas with poor sanitation and the appropriate snail hosts. [CCDM, p. 554-5] Most humans have mild infections. [Harrison ID, p. 1148] Most cases in travelers are acquired in sub-Saharan Africa. People are infected while swimming, bathing, or wading in freshwater in endemic areas. Prevalence rates can exceed 50% in some areas, e.g., Burkina Faso, Mali, Lake Malawi, Lake Tanganyika, Lake Victoria, Omo River, Zambezi River, and the Nile River. Control programs are effective, but there are no international guidelines for certification of elimination. [CDC Travel, p. 338-40]
DIAGNOSTIC
Katayama fever in travelers: highly sens/spec serological tests available from CDC (FAST-ELISA & EITB); Established infection: clinical + ova in stool or urine; Also, serological tests and detection of antigen in body fluids; [Harrison ID, p. 1150]
SCOPE
S. mansoni in Africa, Arabian Peninsula, Brazil, Suriname, Venezuela, and some Caribbean islands; S. japonicum in China, the Philippines, and Sulawesi in Indonesia; [CCDM]
SIGNS & SYMPTOMS
-
>fatigue, weakness
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>fever
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>myalgia
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G abdominal pain
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G blood in stool
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G constipation
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G diarrhea
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G hematemesis
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G hepatomegaly
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G jaundice
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G liver function test, abnormal
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G nausea, vomiting
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H anemia
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H eosinophilia
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H leukocytosis
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H lymphadenopathy
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H splenomegaly
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N confusion, delirium
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N headache
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N seizure
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R chest pain
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R cough
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R dyspnea
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S papules or plaques
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S rash (exanthem)
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S urticaria
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X lung infiltrates
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*bowel obstruction
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*brain abscess or lesion
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*cancer
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*cirrhosis
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*encephalitis
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*glomerulonephritis
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*myelitis
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*myocarditis
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*paralysis
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*pericarditis
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*stupor, coma
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*uveitis
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*weight loss
ENTRY
Skin or Mucous Membranes (Includes Conjunctiva), Swimming
SOURCE
Waterborne (Ingesting, Inhaling, or Swimming)
RESERVOIR
Cattle, Goats and Sheep, Cats, Dogs, Horses, Rodents, Swine, Human
RISK FACTORS
- Swim in contaminated water (skin)
- Travel to endemic area
REFERENCES FOR CASES/YEAR
1.
2. (Global) 243 million required treatment in 2011; [WHO website] 200-300 million infected by schistosomes; [Harrison ID, p. 1146] In Sub-Saharan Africa, 54 million are infected and 393 million at risk for infection by S. mansoni; [http://www.who.int/schistosomiasis/epidemiology/table/en/]
Hepatic and intestinal schistosomiasis is also caused by S. japonicum (China, Indonesia, and the Philippines), S. intercalatum (10 countries in Africa), and S. mekongi (Cambodia and Laos); S. mansoni is found in 55 countries (Arabian peninsula, Egypt, Libya, Sudan, and Sub-Saharan Africa; For calculation, see urinary schistosomiasis;