This is a parasitic worm infection that is acquired by skin contact with infested fresh water. Fresh water snails release microscopic infective parasites into the water that penetrate skin on contact. The snails usually live on weed and stones near the surface of water - but not exclusively. Currents can spread the parasites to areas well away from the contaminated water.
The infection occurs in fresh water lakes, ponds, rivers and streams in Africa, South America and parts of the Middle and Far East, particularly Lake Malawi, Lake Victoria and the Nile river.
The initial infection usually produces no symptoms but itchy skin can develop where parasites enter the skin. Two to four weeks later fever, diarrhoea, cough or a rash sometimes occur as the parasites move around the body.
Adult worms are 1 -2 cm long and live in the veins around the bladder and bowel for an average of 3 -5 years. Long standing disease can lead to damage of the bladder, kidneys, bowel, liver and genital tract.
The infection is diagnosed by blood, stool and urine tests. Oral medication called praziquantel can cure the infection.
The infection is often missed because most infected people don’t have symptoms until damage occurs several years later. Because of the potential long-term effects of the disease it is therefore recommended that travellers take precautions to prevent infection, rather than rely on treatment.
Recommendations for Travellers
- Check prior to travel if you are visiting regions where schistosomiasis occurs.
- Swim only in chlorinated swimming pools or safe sea water in affected areas.
- Check to ensure water facilities (showers, baths etc) at accommodation/recreational facilities are safe (many hotels/facilities draw water directly from nearby lakes, untreated this water can transmit schistosomiasis).
- Avoid activities in affected regions that may involve direct water contact, this includes paddling, swimming, diving, snorkeling, rafting, canoeing, water sports etc.
- Avoid drinking infected water, stick to bottled, boiled water instead.
- Visit your GP for screening tests on return to the UK if you are concerned you have been exposed. Early treatment stops the risk of long-term damage.
Buy treatment for schistosomiasis overseas. This is often sold in resorts and is either counterfeit, taken at the wrong dose or taken too early to cure infection – the drug only works when taken 8 weeks after exposure.
Use insect repellent to prevent infection. There is no evidence that this works and most repellent is water-soluble and so will simply wash off.
Rely on vigorous towel drying of skin after water contact – there is no reliable evidence to prove that this works.
Rely on other travellers/locals to inform you if a water source is infected or not – try and find out from an official/reliable source.