Onchocerciasis is tackled by controlling the blackfly and by preventive mass drug administration with the worm medication ivermectin. According to WHO figures, up to 99 million people in endemic countries – mainly in Africa – are now receiving this therapy on a regular basis, with coverage currently at 76 per cent. WHO estimates that this programme prevents around 40,000 cases of onchocerciasis-related sight loss every year. Some Latin American regions have already succeeded in interrupting the transmission of onchocerciasis and eliminating the disease.

In terms of the disease burden, schistosomiasis (bilharziasis) is the most significant tropical disease after malaria. It is caused by infection with blood flukes, worms of the genus Schistosoma, which are transmitted by infected freshwater snails. The water is contaminated by the excretions (faeces and urine) of humans carrying the infection. These parasites penetrate the skin and migrate through the body. The inflammation resulting from Schistosoma eggs mainly damages the intestines and the urogenital system, becomes chronic and is in some cases fatal.