Observations on Simulium neavei Roubaud, with special reference to a focus of onchocerciasis in the Belgian Congo

Abstract

Parts of a district situated in the tropical rain-forest of the Belgian Congo in which onchocerciasis was generally endemic, were investigated to identify the vector and to ascertain its phoretic host, breeding places, habits, etc.The vector found biting human bait (usually less than 1 metre from the ground) was Simulium neavei Eoub. Dissection of adult females revealed developmental forms of Onchocerca volvulus.Larvae and pupae were found on crabs of the genus Potamon in fast-flowing stretches of the numerous small streams flowing into the Eiver Congo. The infested streams in the main focus of onchocerciasis were treated by DDT emulsion at a concentration of one part per 500,000 for 30 minutes, every ten days for ten applications.The good results observed initially were partly offset by the reappearance six months later of small numbers of Simuliids apparently developing from eggs laid by females entering the disinfested area from without.