> - parasitic disease affects >200 million people ; global impact second to malaria > - 200,000 deaths per year, survivors with chronic morbidity > - 90% of infections occur in africa **vector:** infected *freshwater snails* release larvae → penetrate human skin who come in contact with the water → Schistosomula then circulate in the blood and replicate in the portal vessels → migrate to blood vessels in other parts of the body and release their eggs, some of which are shed in human faeces and end up back in the surface waters → eggs hatch in the water and produce miracidia, which enter suitable freshwater snails → cycle repeats itself as they release cercariae again. # symptoms - Acute infections are more likely to cause symptoms among non-residents of endemic areas. - A pruritic rash in response to cercariae entering the skin (swimmers’ itch) can occur within a day, usually subsiding within 10 days. - **Acute toxaemic schistosomiasis** (Katayama fever) is an uncommon but often severe seroconversion illness that may occur 1 to 3 months after the primary infection. - Symptoms include fever, malaise, urticaria, cough, diarrhoea, hepatosplenomegaly and lymphadenopathy. - It may last several weeks. # diagnosis The diagnosis is made by a *history of freshwater exposure* and the demonstration of* eggs in the urine or faeces*. During Katayama fever, no eggs may be seen. Serological tests are available. Abdominal x-rays may show bladder calcification in chronic genitourinary schistosomiasis. # Treatment - **Praziquantel** (40 to 60 mg/kg in two divided doses) is an effective treatment but, due to the high rate of re-infection, it may be difficult to achieve a cure in endemic areas. - During Katayama fever, **prednisone** may be given to suppress the acute reaction and a repeat dose of praziquantel is recommended after 1 to 2 months