schistosomiasis

introduction

also known as bilharzia, bilharziosis or snail fever
it is a parasitic disease caused by several species of trematodes (platyhelminth infection, or “flukes”), a parasitic worm of the genus Schistosoma.
snails serve as the intermediary agent between mammalian hosts.
the disease is found in tropical countries in Africa, the Caribbean, eastern South America, Southeast Asia and in the Middle East.
the greatest risk of infection for tourists appears to come from exposure to freshwater in Africa, especially Lake Malawi.
it is the second most socioeconomically devastating parasitic disease after malaria, infecting more than 207 million people, 85% of whom live in Africa.
it is endemic in Egypt, exacerbated by the country's dam and irrigation projects along the Nile.
- Rx with tartar emetic using unclean needles in the late 1950's - 1980's resulted in Egypt having the highest rate of hepatitis C infection in the world.
children may acquire the disease by swimming or playing in infected water

schistosomiasis often is a chronic illness that can damage internal organs and, in children, impair growth and cognitive development.
most infected travellers are asymptomatic and at low risk of complications because of low parasite burdens
Katayama fever is associated with the migration of schistosome larvae throughout the body (symptoms include fever, chills, malaise, headache, cough, abdominal pain, diarrhoea, urticaria, and occasionally neurological disorders

the intestinal form is caused by:
- Schistosoma mansoni - parts of South America and the Caribbean, Africa, and the Middle East;
- Schistosoma intercalatum - central West Africa
- Schistosoma japonicum - Far East
- Schistosoma mekongi - Southeast Asia

caused by Schistosoma haematobium which is found in Africa and the Middle East
is associated with increased risks for bladder cancer in adults
once egg deposition begins, clinical features include haematuria, haematospermia, urgency, frequency, terminal dysuria, salpingitis, prostatitis and chronic genital ulcers
more serious but rare complications are paraparesis, paraplegia and mass cerebral lesions
immigrants and refugees from endemic countries are likely to have much heavier infection loads and may present with the complications of chronic fibrosis, such as ureteric obstruction and portal hypertension

the standard treatment is praziquantel (20 mg/kg orally for two doses, four hours apart)
10%–15% of patients require re-treatment