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Bilharzia disease (schistosomiasis) in returning travellers

14 June 2013

The Travel Health team at InterHealth have diagnosed bilharzia disease (schistosomiasis) in a number of travellers returning to the UK from Africa in recent weeks.

The lure of swimming or paddling in Lake Malawi and other freshwater bodies often proves too hard to resist despite them harbouring the snails that release the larvae which cause bilharzia.

The World Health Organisation reports that 243 million people required treatment for bilharzia disease in 2011. It is estimated that at least 90% of those requiring treatment for bilharzia live in Africa and, worldwide, around 200,000 people die from the disease annually.

Where is bilharzia present?

·    Africa: in freshwater bodies in southern and sub-Saharan Africa–including the Great lakes and rivers as well as in the Mahgreb region of North Africa and the Nile River valley in Egypt and Sudan.
·    South America: Brazil, Suriname, Venezuela.
·    Central America & the Caribbean: Dominican Republic, Guadeloupe, Martinique, Puerto Rico, Saint Lucia.
·    Middle East: Iran, Iraq, Saudi Arabia, Yemen.
·    Asia: Cambodia, southern China, Laos, the Philippines & Sulawesi.

Bilharzia disease – outline information

Bilharzia is prevalent in tropical and sub-tropical areas, especially in poor communities without access to safe drinking water and adequate sanitation. Larvae penetrate the skin of people in the water and go on to develop into adult schistosomes and live in blood vessels. Female schistosomes release eggs. Some of these are released in urine or faeces while others are trapped in tissue in the body.  Symptoms of the disease are caused by the body’s immune reaction to these eggs, although some people may not experience any symptoms for a long time after they become infected.

In urogenital schistosomiasis gradual damage can occur to the bladder, ureter and kidneys. In intestinal schistosomiasis, the liver and spleen can become progressively enlarged and there is intestinal damage.

Bilharzia is treated with the drug Praziquantel which is very effective and has few side-effects.

Advice for those travelling to or working in the areas affected:

·    Avoid swimming, paddling or washing in freshwater in risk areas even when local tourism organisations state that there is no bilharzia in the area.
·    Swimming in chlorinated pools or the sea does not pose a risk of bilharzia, although other risks may be present which you should be aware of eg currents, depth of water, etc.
·    Schistosomiasis parasites can be killed by heating the water to 50°C for 5 minutes or leaving the water to stand for at least 48 hours.
·    If, despite the risks, you decide to swim in a freshwater lake, the risk of contracting bilharzia is lower if you swim in the centre of the lake rather than on the shore where the risk is highest.
·    If you think you may have been exposed to bilharzia you should ask to be tested for the disease even if you are not currently experiencing any symptoms.

For further advice please click on the related information topics on the right hand panel of this screen.

Sources:

World Health Organisation, ProMED mail, NaTHNaC, Centers for Disease Control & Prevention (CDC)

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