What is Schistosomiasis?
Schistosomiasis (or Bilharzia) is a parasitic disease caused by a flatworms or blood flukes, known as schistosomes. There are five species, the most prevalent being Schistosoma mansoni and S. haematobium.
Schistomiasis is transmitted to humans via skin contact with contaminated fresh water in which certain types of snails live. Schistosome eggs contaminate the water when infected persons urinate or defecate in or near the water. The eggs hatch and parasites called miracidia then invade the host snail, grow and develop. After leaving the snail, the parasites are viable for 48 hours and penetrate the skin of humans directly on contact. Once the parasite penetrates the skin, it migrates to either the veins of the intestines or the bladder.
Swimming or bathing in inland freshwater lakes, pools and river tributaries is the main cause of infection. Most infections in Australian travellers originate in Africa, but cases also occur in South America and South-east Asia, wherever the host snails are found.
Incidence
The disease affects over 200 million people worldwide in tropical and sub-tropical regions and the number is rising, particularly in Africa.
Symptoms
- Most infected travellers have only a light infection and may exhibit no symptoms
- Local irritation at the site of parasite entry (known as ‘swimmer's’ itch’)
- Fever and illness from four weeks after contact with water. A dry cough is often a feature of this stage of the infection
- Lethargy and weight loss
- Blood in urine or stools once the disease is established
Prevention
- Do not swim or wash in fresh water that is potentially infected
- Quick drying of any exposed skin may kill any larvae before they can penetrate the skin. Rubbing down with alcohol will further reduce the risk of infection
- Fast flowing water is less risky than still or slow-moving water
- Wearing wetsuits or bodysuits will reduce the risk of penetration
- If you need to wade through water, wear high rubber boots
- Treat any fresh water needed for washing by first boiling it for 10 minutes
- Water that has been left to stand for 3 days is safe provided it contains no snails
- Saltwater and chlorinated water is safe
- No vaccination is available to prevent the disease
Treatment
Specific medications are available to treat the disease.
A blood test 3 months after any freshwater exposure in risk areas is recommended to detect early infection.
Fellow travellers should be tested.
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