The Onchocerciasis Control Programme of the World Health Organization uses larvicides to fight against the aquatic stages of the vector Simulium damnosum s.l., and thereby interrupt transmission of the disease. Since the appearance of resistance to Abate and chlorphoxim in certain cytotypes of the vector, the efficacy of many possible replacement insecticides has been tested and the impact of the best of them (permethrin, cyphenothrin, pyraclofos, and carbosulfan) on the aquatic fauna evaluated.