Many middle-income countries have made great progress in the control of the tropical worm disease schistosomiasis, but political commitment and strong health systems are now needed to help countries with fewer resources, state the authors of a Seminar in this week's issue of the Lancet.

Schistosomiasis is a wide-spread parasitic disease caused by infection with flatworms. The disease mainly affects people living in tropical countries that come into contact with infested waters but it can also affect travelers. Up to 200 million people are estimated to be infected worldwide. Dependent of the species of worm and stage of disease, symptoms may include diarrhoea, liver damage and portal hypertension, or bloody urine, and bladder/kidney damage.

Wide-scale drug treatment combined with socio-economic progress has greatly reduced the impact of schistosomiasis in middle-income countries such as Egypt, China, Brazil, the Philippines and Morocco. However, low-income countries, especially those in sub-Saharan Africa, have had greater difficulties in implementing and sustaining drug-based control strategies. Early pilot projects in countries such as Mali and Madagascar showed promising early results but floundered when foreign assistance ended.

Author Professor Bruno Gryseels states: "The fight against schistosomiasis is not just a matter of distributing drugs; establishment of strong health systems that are able to take care of patients and to integrate sustainable control measures is a far greater and more important challenge."