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Section 3. Summaries of Infectious Diseases
Schistosomiasis
Clinical ManifestationsEtiology
Epidemiology
Diagnostic Tests
Treatment
Isolation of the Hospitalized Patient
Control Measures
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CLINICAL MANIFESTATIONS
Initial entry of the infecting larvae (cercariae), which are shed by snails, is through skin and may be accompanied by a transient, pruritic, papular rash (cercarial dermatitis). After penetration, the organism enters the bloodstream and migrates through the lungs. Each of the 3 major human schistosome parasites lives in some part of the venous plexus that drains the intestines or the bladder. Four to 8 weeks after exposure, an acute illness can develop that manifests as fever, malaise, cough, rash, abdominal pain, hepatosplenomegaly, diarrhea, nausea, lymphadenopathy, and eosinophilia (Katayama fever). The severity of symptoms associated with chronic disease is related to the worm burden. People with low to moderate worm burdens may never develop overt clinical illness; people with significant worm burdens can have a range of symptoms caused primarily by inflammation and fibrosis triggered by eggs produced by adult worms. Heavy infection can result in mucoid bloody diarrhea accompanied by tender hepatomegaly. Portal hypertension can develop from intestinal forms of schistosomiasis and can cause hepatosplenomegaly, ascites, and esophageal varices and hematemesis. Long-term involvement of the colon produces abdominal pain and bloody diarrhea. In Schistosoma haematobium infections, the bladder can become inflamed and fibrotic. Symptoms and signs include dysuria, urgency, terminal microscopic and gross hematuria, secondary urinary tract infections, and nonspecific pelvic pain. An association between S haematobium and bladder cancer has been established. Other organ systems can be involved from embolized eggs, for example, to the lungs, causing pulmonary hypertension; or to the central nervous system, notably the spinal cord in Schistosoma mansoni or S haematobium infections and the brain in Schistosoma japonicum infection.
Cercarial dermatitis (swimmer’s itch) is caused by the larvae of nonhuman schistosome
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Red Book 2009 2009: 783-816.