The daily educational pearl – Schistosomiasis

Schistosomiasis aka bilharziasis, snail fever

– caused by blood flukes of genum Schistosoma – 2 big groups, one that causes gastrointestinal disease and one that causes urogenital disease

– transmitted via freshwater – freshwater snails act as intermediate hosts; they release the larval form of the parasite (cercariae) in water; the larvae penetrate the wet, intact skin of people exposed to it or they are ingested during swimming / snorkelling. Even a brief exposure can cause infection.

– found throughout Africa, Middle East, South America, Asia, but very common in sub-Saharan Africa and East Africa fresh water – Lake Malawi, Zambezi River, Lake Kariba; and in Asia – Mekong River; there is a significant increase in the number of cases with the development of adventure tourism

Clinical features:

* pruritic rash – usually occurs soon after exposure

* haematuria if infection is caused by one of the species that cause urogenital disease

* “Katayama fever” or acute schistosomiasis – fever, night sweats, dry cough, abdominal pain, headache, anorexia, weight loss, diarrhoea; hepatosplenomegaly

Chronic infection: mature adult worms remain in the venous system and deposit eggs in various body tissues (brain, skin, liver) causing:

– hepatosplenomegaly, hepatic fibrosis, portal hypertension, gastro-oesophageal varices

– seizures, various neurological defficits

– dysuria, frequency, haematuria, bladder calcification

 

Investigations:

–          Eosinophilia (non-specific)

–          Serology (but seroconversion can take up to 6 months)

–          Ova detection in urine or faeces (terminal urine tested for 10 days, ideally collected in the middle of the day (12 to 2 pm) when ova release is maximal)

 

Treatement: praziquantel

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