Aedes (Stegomyia) aegypti Linneus and Aedes (Stegomyia) simpsoni (Theobald complex) together with Aedes (Stegomyia) africanus Theobald play a leading role in the epidemiology of yellow fever (YF) in Africa. The ecological, morphological and behavioral diversity of at least two of these mosquito groups have an impact on the distribution of human YF in the region. In West Africa Ae. aegypti is responsible for urban YF, whereas in East Africa Ae. eagypti has never been incriminated in YF transmission. In East Africa Ae. aegypti occurs in human-biting (anthropophilic) and non-human-biting (non-anthropophilic) forms. But even where it readily bites humans, at the East African Coast, YF outbreaks are absent. Ae. simpsoni complex is widely spread in Africa south of the Sahara. Like Ae. aegypti, it occurs in anthropophilic and non-anthropophilic behavioral forms. In Ethiopia several strains of YF virus were isolated from it in the 1960’s. Ae.simpsoni was incriminated as the vector in the greatest epidemic of YF in Africa, which occurred in Ethiopia between 1960 and 1962. In Kenya, Ae. Simpsoni was among the species incriminated in the YF outbreak in 1992/1993. In most parts of Uganda, Ae. simpsoni non-anthropophilic behavior is probably responsible for the almost complete absence of human YF cases in these parts. Ae. africanus is also widely distributed, but the diversity of its morphological and behavioral forms is not well documented. The current extensive deforestation in many parts of Africa is encouraging Ae. africanus to become peridomestic. The distribution of the different polymorphs and different biting behavioral forms of Ae. africanus in Africa is not very clear, nor have vector competence studies been carried out with the different forms from different locations of the distribution range. YF is still wide spread in Africa. The circumstances and possible hazards are worth serious concern.
Buy this Article