Species complex of vectors and epidemiology.

This work collates previous and recent cytotaxonomically defined segregates of the Simulium damnosum complex from western and eastern Africa. Standard cytotaxonomic procedures were used on new samples from Nigeria, Cameroon and Malawi. The main onchocerciasis vectors comprising cytotypes, cytoforms and cytospecies are highlighted and indications of host preferences are given. Thyolo form, the vector implicated in the Thyolo Highlands of Malawi, is reported for the first time. Also reported are new foci of two genetically distinct savanna taxa: Volta form and S. damnosum s.s.. The associations between forest taxa and onchocerciasis in the Forest Zone of west Africa together with the interplay of vector distributions at the interface of this and the Savanna Zone in relation to the epidemiology of onchocerciasis are discussed. The role of individual members of the species complex in epidemiology is less understood in east Africa and the Yemen but is briefly discussed.