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About Schistosomiasis, MAHECAS UK

Malawi Health Care Support UK

UK Registered Charity Number 1057994

Schistosomiasis

Schistosomiasis; Bilharziasis

Hospital in Malawi

Schistosomiasis, (a.k.a. Bilharziasis), is common in Africa and Asia. It is caused by blood flukes, (flatworms). Two types of this disease are common to Africa.

Mason's schistosomiasis is caused by intestinal blood flukes, Schistosoma mansoni. These live in the veins surrounding the intestines, and pass eggs out through faeces. They infect humans by absorption through the skin, (i.e. touch).

Vesical schistosomiasis is caused by urinary blood flukes, Schistosoma haematobium. These are similar but eggs escape the body in urine by breaking through vein walls into the bladder.

Female flukes lay between 300 and 5,000 eggs daily into the bloodstream. These find their way to the bladder or intestine, and are excreted from the body. On contact with fresh water, they hatch and swim about to find an appropriate host, (usually a snail). There they develop further then leave as larvae. On contact with mammals, they enter the skin shedding their tail, and find their way to the blood stream. Here they feed and the process is repeated.

The disease can be caught swimming in waters populated by schistosome carrying snails. It can also be caught by contact with improperly treated water, so is common in rural areas.

The first symptoms usually occur as an allergic reaction to the parasites and their by-products. Such symptoms may include

coughing, skin eruptions, swelling and tenderness of the liver and fevers (usually in the afternoon and evening)
The disease may then develop to a chronic stage. This happens with a build up of the parasite's eggs. They can then become packed into the walls of blood vessels and organs. This leads to a fibrous thickening of the walls. The walls also lose their elasticity. Liver damage or stone formation in the bladder can then occur, (dependent on the type of flukes present). Eggs spread to all parts of the body, and can cause legions even within the brain and lungs.

Treatment is usually by chemotherapy. This is aimed at killing the adult flukes producing the eggs. Untreated the flukes have life spans of up to 25 years.

Behind malaria, it is the next most serious parasitic infection for humans. The World Health Organisation, (WHO), believe there are around 200 million people infected worldwide. (This includes a 3rd type of schistosomiasis mainly found in the far-east.)