Malaria and dengue vector biology and control in Southern and Eastern Africa

Abstract

Malaria vector control has been practiced in the eastern/southern half of the African continent since the beginning of the 20th century, from larval control in the north (Sudan, 1901) to adult control in the south (South Africa, 1931). The major vectors are Anopheles gambiae, An. funestus and An. arabiensis, with An. merus, An. bwambae and An. nili implicated in transmission in localized areas. Current vector control methods include indoor residual house spraying (+/- 9 countries out of 19), insecticide-treated bednets for personal protection (+/- 15 countries out of 19), larviciding under certain circumstances and very limited environmental management. Control programmes are faced with multifaceted problems such as service delivery, species diversity and identification, and insecticide resistance. Population-genetic studies are limited compared with West Africa and this gap in knowledge should be urgently addressed. Current evidence suggests far less polymorphism in all three major vectors, An. gambiae, An. arabiensis and An. funestus, than is seen in West- African populations. As far as non-malaria disease vectors are concerned, both Aedes aegypti aegypti and Ae. aegypti formosus occur in East and Southern Africa. Genetic and diseasetransmission studies provide strong evidence for the specific distinctness of these subspecies. Occasional cases of suspected dengue occur in Kenya, presumably transmitted by Ae. aegypti. Outbreaks of yellow fever, however, have been caused by other Aedes species and not the above two. No targeted control activities are carried out against these species