Malaria vectors in the Greater Mekong Subregion: overview of malaria vectors and remaining challenges

Abstract

Malaria transmission in the Greater Mekong Subregion depends on, among other factors, vector behavior and ecology, and the degree of contact between humans and the Anopheles mosquitoes. This chapter will review and update knowledge presented in the 2003 Mekong Malaria monograph for planning and implementing evidence-based vector control programs. Collation of 150 publications and reports showed that the highest number of vector species reported included An. minimus Theobald complex (26.74%), An. dirus Peyton and Harrison (14.26%), An. sundaicus (Rodenwaldt) (5.65%), An. sinensis Wiedemann (4.29%), An. maculatus Theobald (4.23%), An. philippinensis Ludlow (1.62%), An. annularis Van der Wulp (0.37%), An. campestris Reid (0.25%), and An. lesteri Baisas and Hu (=anthropophagus) (0.045%). Other Anopheles species accounted for 44.44%. Anopheles dirus was incriminated as a vector of Plasmodium knowlesi malaria in Viet Nam for the first time, but remained a suspected simian vector in other countries in the region. Well-designed trials of innovative strategies in intractable and difficult situations are needed, including a better understanding of the various causal relations and interactions between physiology, environment, and vector bionomics. While current front-line vector control interventions have contributed significantly to a worldwide decrease of malaria, indoor residual spraying and insecticide-treated bednets/ long lasting insecticidal bednets have had variable impact on exophilic/exophagic and/or early biting vectors. As vectors' responses to control measures vary in different areas, entomological studies on the efficacy of insecticide-treated bednets and other innovative control tools to ensure that strategies are tailored to local circumstances. Given that current tools are insufficient to break transmission cycles, more strategic investments into research on outdoor transmission, monitoring of insecticide resistance, vector species identities, vector mapping, target profiles of new control technologies and delivery systems are required.