Classification: ICD-9 120; ICD-10 B65
Syndromes and synonyms: Bilharziasis, Katayama fever or syndrome, urogenital and intestinal schistosomiasis.
Agent: Trematode worms Schistosoma mansoni, S. haematobium, S. intercalatum, and S. guineensis (formerly known as S. intercalatum). S. haematobium species group contains 8 species, of which not all cause human disease.
Reservoir: Humans are the main reservoir. S. haematobium can infect primates, livestock and rodents. S. mansoni, S. intercalatum, and S. guineensis can infect rodents.
Vector: Freshwater snails: Biomphalaria spp. for S. mansoni, Bulinus spp. for S. haematobium, S. intercalatum, and S. guineensis. Technically, humans are the ‘vector’ as they harbor the parasite’s sexual stage. Snails are intermediate hosts.
Transmission: Contact with freshwater bodies containing cercariae that penetrate skin or mucous membranes; drinking contaminated water (uncommon).
Cycle: Snail–human–snail. Infected humans shed eggs into the water, which hatch into larvae (miracidia) that enter snails and develop into motile larvae (cercariae). The cercariae are shed into the water and penetrate the skin of humans in the water, enter the bloodstream and settle in the liver. When matured to adult male and female worms, they migrate to the abdominal veins (S. mansoni, S. intercalatum, S. guineensis) or pelvic veins (S. haematobium
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