Field Evaluation of a Push-Pull System to Reduce Malaria Transmission

Abstract

Malaria continues to place a disease burden on millions of people throughout the tropics, especially in sub-Saharan Africa. Although efforts to control mosquito populations and reduce human-vector contact, such as long-lasting insecticidal nets and indoor residual spraying, have led to significant decreases in malaria incidence, further progress is now threatened by the widespread development of physiological and behavioural insecticide-resistance as well as changes in the composition of vector populations. A mosquito-directed push-pull system based on the simultaneous use of attractive and repellent volatiles offers a complementary tool to existing vector-control methods. In this study, the combination of a trap baited with a five-compound attractant and a strip of net-fabric impregnated with micro-encapsulated repellent and placed in the eaves of houses, was tested in a malaria-endemic village in western Kenya. Using the repellent delta-undecalactone, mosquito house entry was reduced by more than 50%, while the traps caught high numbers of outdoor flying mosquitoes. Model simulations predict that, assuming area-wide coverage, the addition of such a push-pull system to existing prevention efforts will result in up to 20-fold reductions in the entomological inoculation rate. Reductions of such magnitude are also predicted when mosquitoes exhibit a high resistance against insecticides. We conclude that a push-pull system based on non-toxic volatiles provides an important addition to existing strategies for malaria prevention.

Eave Screening and Push-Pull Tactics to Reduce House Entry by Vectors of Malaria

“…Both experiments were carried out in Kigoche village in Kisumu County, Kenya (00°08′19′ S 34°55′50′ E, altitude: 1,160 m) (as previously described 16,31 ). Kigoche village is located within the Ahero rice irrigation scheme and typically experiences two rainy seasons: long rains between March and August and short rains between October and November, with an average annual rainfall of between 1,000 and 1,800 mm.…”

“…The design of an effective push-pull system directed at malaria vectors is a recent, and ongoing, development. 15,16 Throughout the tropics, many traditional houses are constructed with eaves (openings between the top of the wall and the roof), which serve to increase airflow in the houses, but also form the predominant entry point for anopheline mosquitoes. [17][18][19] Reducing mosquito house entry by screening eaves and other openings has played a well-documented role in reducing the incidence of malaria in many different countries around the globe.…”

“…The impregnated textile material could then be used to fabricate bed nets or eave screens. 26,27 Menger and others 16 showed that a narrow strip of cotton net fabric that was impregnated with microcapsules containing delta-undecalactone (dUDL) and placed in the eave of traditional houses in western Kenya reduced mosquito house entry by 50% or more. The repellency of dUDL against anopheline and other mosquitoes has been previously demonstrated in *Address correspondence to Alexandra Hiscox, Laboratory of Entomology, Wageningen University and Research Centre, P.O.…”

“…It would not be necessary for eave screens impregnated with a long-lasting spatial repellent to close off all holes and cracks in the wall of a house as the impregnated screens would provide a chemical barrier as well. 16 We hypothesized that the combined application of eave screening and push-pull might yield an intervention, which is suitable for use in traditional homes in rural Africa and which is superior over either approach alone.…”

“…[29][30][31] An ongoing large-scale intervention study explores the potential of mass-trapping malaria vectors to reduce malaria transmission on an island community in western Kenya. 32 By actively removing mosquitoes from the peridomestic environment, attractant-baited traps can provide a dual-protective effect: 1) a direct effect by reducing house entry of mosquitoes that would otherwise have entered 16,33 and 2) an indirect effect by reducing the average mosquito's life span and by depleting mosquito populations through daily removal trapping. 34,35 A pilot experiment in which a human-occupied house in a semifield setup was fully screened (eaves and other openings) and equipped with an attractant-baited trap hanging outside the house indicated that this approach could dramatically reduce house entry of malaria vectors and enhance attractant-baited trap catches.…”