Human schistosomiasis.

Schistosomiasis is a neglected tropical disease caused by infection with blood flukes of the genus Schistosoma. Widely distributed in the Middle East, southeast Asia, Latin America, and (mostly) sub-Saharan Africa, schistosomiasis is acquired upon skin penetration of infective larvae released by freshwater snails. Acute infection might present with self-limiting hypersensitivity reactions (known as Katayama fever). Chronic infection typically leads to two main clinical patterns: intestinal or urogenital schistosomiasis, depending on the infecting species. Impairment of other body sites (eg, the CNS or respiratory tract) can occur. The intestinal form is characterised by abdominal pain and diarrhoea, with or without blood; complications are hepatic fibrosis, portal hypertension, splenomegaly, and variceal bleeding. The urogenital form is characterised by dysuria and haematuria; complications are renal failure and squamous-cell carcinoma of the bladder. Conventional diagnosis is based on egg detection in faeces or urine, although sensitivity might be low. Praziquantel is the first-line treatment, and it is also provided in preventive chemotherapy campaigns by mass drug administration to afflicted communities.