Further studies on the reinvasion of the onchocerciasis control programme by Simulium damnosum s.l.: the effects of an extension of control activities into southern Ivory Coast during 1979.

During 1979 the aerial larviciding operations of the Onchocerciasis Control Programme were extended southwestwards to cover those areas with Ivory Coast where the savanna cytospecies of the Simulium damnosum complex were known to breed. This resulted in a marked reduction of the reinvasion which threatened the Programme in Ivory Coast and Upper Volta in earlier years. Previous conclusions concerning the location of sources of invading populations and consequently the direction and distance of the movements of flies were substantiated. It was confirmed that S. damnosum s. str. and S. sirbanum were the main migrant species. In this area S. Squamosum was shown to be of much less importance as a migratory vector.