Malaria and dengue vector biology and control in West and Central Africa

Abstract

In West and Central Africa endemic malaria and epidemic yellow fever are still main causes of morbidity and mortality. From Dakar in Senegal to Kinshasa in the Democratic Republic of Congo the pattern of malaria transmission shows a huge variability, in term of dynamics (rhythm and intensity) of transmission, as well as in terms of the vector species involved. The Plasmodium annual entomological inoculation rates (EIR) vary from less than one to more than 1000 infectious bites per person and P. falciparum represents more than 90% of malaria infections. In most settings south of the Sahara, several vector species are sympatrically involved in malaria transmission either simultaneously or replacing each other seasonally (Coluzzi 1984; Fontenille and Simard 2004). These vectors differ greatly in terms of density and vector efficiency. Despite an efficient vaccine, deadly outbreaks of Yellow Fever (YF) virus, which circulates among monkeys and sylvatic vectors, still occur occasionally from Cameroon to Senegal (Mutebi and Barrett 2002). Although Aedes aegypti, the local vector, is abundant, and Dengue 2 virus is present in the forest, human dengue remains very rare and localized in Western Africa. But the situation could worsen with the recent introduction and spreading of Ae. albopictus, a potential dengue vector, in Central Africa. Any vector control strategy, whether based on traditional (insecticides and impregnated/treated nets) or genetic control strategies (sterile-male releases or introduction of transgenic mosquitoes), aiming at significantly reducing malaria burden or yellow fever/dengue occurrence in Africa, will have to account for such entomological heterogeneity added to ecological and socio-economic diversities. This paper provides an update on the bionomics and genetics of the four major African malaria vector systems (the Anopheles gambiae complex and the An. funestus, An. nili and An. moucheti species groups) and of the Ae. aegypti and Ae. albopictus species. It also reviews current vector control measures against malaria and yellow-fever vectors