Current and Future Prospects for Preventing Malaria Transmission via the Use of Insecticides

Abstract

Malaria vectors have developed resistance to all classes of insecticides that are used to target the adult mosquito to prevent parasite transmission. The number of resistant mosquito populations has increased dramatically in recent years, most likely as a result of the scale-up of vector control activities, and the intensity of this resistance is increasing rapidly and compromising the performance of vector control tools. Bednets and indoor residual spray formulations containing alternative active ingredients have shown promise in field trials but are still several years away from implementation. As existing insecticides become less effective at killing mosquitoes in the countries with the highest burden of malaria, there is growing concern that the advances made in reducing malaria transmission will be eroded by insecticide resistance. The likelihood of this scenario, and strategies that may help mitigate against this, are reviewed below.

Figure 1.

Pyrethroid resistance in malaria vectors. Flags indicate mortality in WHO bioassays (red <90% mortality, orange 90%–97% mortality, green >97% mortality). Data shown are from 2011 to 2016 (Source: IR Mapper [www.irmapper.com], September 2016).

Figure 2.

Improvement in malaria indicators in Bunkpurugu-Yunyoo, Ghana between 2010 and 2013 after a switch in insecticide class from pyrethroids to carbamates for indoor residual spraying. (Source: President’s Malaria Initiative 2015.) RTD, Rapid diagnostic test; IRS, indoor residual spraying.