Schistosomiasis

Abstract

Schistosomiasis is a neglected, tropical, vector-borne, water-borne disease caused by helminth parasites of the genus Schistosoma. It is globally distributed, still reported from 78 countries, and estimated to affect over 200million people. Schistosomes have complex life cycles, entailing snail intermediate hosts; some schistosome species have animal reservoirs, which makes public health control more challenging. Humans contract the infection following contact with freshwater contaminated with larval stages of the parasite. Morbidity is mainly caused by granulomatous reactions to the parasite's eggs trapped in organ tissues and the resulting fibrosis. Two main clinical forms exist: intestinal and urinary (or urogenital) schistosomiasis. Detection of parasite eggs in the stool and urine is the gold standard for diagnosis, although a wide range of tests and diagnostic techniques have been developed and are available. The anthelminthic praziquantel is the treatment of choice against all the species of schistosomes. Its mass administration at regular intervals to populations living in endemic areas (preventive chemotherapy) is the mainstay of WHO's strategy for public health control of schistosomiasis, with over 105million treated in 2019. Snail control, access to water and sanitation, environmental management, health education, chemoprophylaxis and treatment of animal reservoir are complementary public health interventions. No vaccine is currently available. The new road map for neglected tropical diseases 2021–30 lists schistosomiasis among the diseases targeted for elimination as a public health problem by 2030.