Urogenital schistosomiasis
Presentation and recommendations by ANSES
Urogenital schistosomiasis (bilharziasis) is a parasitic disease due to trematode flatworms of the genus Schistosoma. It can be transmitted to humans through simple skin contact with water in bodies of water or waterways (streams, rivers, lakes or ponds) in which freshwater gastropod snails of the genus Bulinus live. When infested, these snails disperse larvae into the water. Following reports of clustered cases of indigenous schistosomiasis in southern Corsica due to Schistosoma haematobium, ANSES has been asked to assess the risk of human contamination by this parasite in continental France so that it can rapidly take action to control any possible risks. To do so, the Agency has conducted an expert assessment of the ecology of the Bulinus snail, and its expert assessment work has led it to recommend acquiring further knowledge on these molluscs in order to provide a comprehensive review of their presence in bodies of water and waterways conducive to their development. This knowledge is essential for establishing a profile of the different water sites likely to provide conditions that could promote S. haematobium transmission. In the meantime, measures should be implemented to prevent water contamination and/or avoid exposure.
Urogenital schistosomiasis: presentation and work by the Agency
Second only to malaria as the most widespread parasitic disease worldwide, schistosomiasis is an infection caused by trematode flatworms of the genus Schistosoma. It can be transmitted to humans through simple skin contact with fresh water in which freshwater gastropod snails of the genus Bulinus live and, when infested, disperse the flatworm’s larvae into the water. Schistosoma haematobium infection affects 112 million people throughout the world, and 150 000 people die each year from the disease.
Following reports of clustered cases of indigenous urogenital schistosomiasis in southern Corsica due to Schistosoma haematobium, the Directorate General for Health (DGS) asked ANSES to assess the risk of human contamination by this parasite in continental France. In parallel, the French High Council on Public Health (HSCP) was also asked by the DGS to study the screening, treatment and prevention of S. haematobium infection.
Since urogenital schistosomiasis is contracted through total or partial immersion of the body in water containing the immature form of the S. haematobium parasite hosted by the Bulinus snail, the Agency has been asked to conduct an expert assessment of the ecology of this mollusc.
Agency conclusions and recommendations
The Agency's expert assessment recommends imperatively drawing up a map in order to describe the population dynamics of the Bulinus snail in waterways and bodies of water throughout France. Such knowledge is indispensable for establishing a profile of the water sites likely to create the conditions which could promote S. haematobium transmission. In the meantime, measures should be implemented to prevent environmental contamination and if necessary avoid exposure. ANSES therefore recommends:
- preventing Schistosoma haematobium eggs from contaminating water environments by avoiding urination in waterways and bodies of water;
- reducing the number of molluscs in waterways and bodies of water through regular collection campaigns if the area to be treated is small enough;
- providing information on how urogenital schistosomiasis is transmitted to workers likely to come into contact with infected water,
- providing workers with personal protective equipment (boots, chaps, gloves, etc.), in order to prevent skin contact with the water of targeted freshwater sites;
- if contamination of a site is confirmed, informing the general public and on-site workers that all contact with the water must be avoided and taking all the necessary measures to prevent exposure. Workers must also be sure to wear personal protective equipment.