Schistosomiases
Schistosomiases are acute or chronic visceral parasitic diseases due to 5 species of trematodes (schistosomes).
The three main species infecting humans are Schistosoma haematobium, Schistosoma mansoni and Schistosoma japonicum. Schistosoma mekongi and Schistosoma intercalatum have a more limited distribution (see table below).
Humans are infected while wading/bathing in fresh water infested with schistosome larvae. Symptoms occurring during the phases of parasite invasion (transient localized itching as larvae penetrate the skin) and migration (allergic manifestations and gastrointestinal symptoms during migration of schistosomules) are frequently overlooked. In general, schistosomiasis is suspected when symptoms of established infection become evident (see table below).
Each species gives rise to a specific clinical form: genito-urinary schistosomiasis due to S. haematobium, intestinal schistosomiasis due S. mansoni, S. japonicum, S. mekongi and S. intercalatum.
The severity of the disease depends on the parasite load. Heavily infected patients are prone to visceral lesions with potentially irreversible sequelae.
Children aged 5 to 15 years are particularly at risk: prevalence and parasite load are highest in this age group.
An antiparasitic treatment should be administered to reduce the risk of severe lesions, even if there is a likelihood of re-infection.
Geographic distribution of schistosomiasis in Africa (WHO)
Parasite/Epidemiology |
Clinical features/Diagnosis (established infection) |
Treatment |
|
Genito-urinary schistosomiasis |
S. haematobium |
|
The same antiparasitic treatment is used for all species: praziquantel PO |
Intestinal schistosomiasis |
S. mansoni S. japonicum S. mekongi S. intercalatum |
|
Ref | Notes |
---|---|
1 | For the treatment of schistosomiasis, praziquantel may me administered to pregnant women. |