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. 3219]
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. 3219-21] 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. 1359] Neurological schistosomiasis is an uncommon complication with symptoms of delirium, seizures, visual and motor defects, myelitis, stupor, and coma. [Cohen, p. 1175] Bleeding esophageal varices occur in a small percentage of patients with cirrhosis. [Guerrant, p. 920]
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. 1237] 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. 309-13]
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