Abstract
Malaria control programs are being jeopardized by the spread of insecticide resistance in mosquito vector populations. It has been estimated that the spread of resistance could lead to an additional 120000 deaths per year, and interfere with the prospects for sustained control or the feasibility of achieving malaria elimination. Another complication for the development of resistance management strategies is that, in addition to insecticide resistance, mosquito behavior evolves in a manner that diminishes the impact of LLINs and IRS. Mosquitoes may circumvent LLIN and IRS control through preferential feeding and resting outside human houses and/or being active earlier in the evening before people go to sleep. Recent developments in our understanding of mosquito swarming suggest that new tools targeting mosquito swarms can be designed to cut down the high reproductive rate of malaria vectors. Targeting swarms of major malaria vectors may provide an effective control method to counteract behavioral resistance developed by mosquitoes. Here, we evaluated the impact of systematic spraying of swarms of Anopheles gambiae s.l. using a mixed carbamate and pyrethroid aerosol. The impact of this intervention on vector density, female insemination rates and the age structure of males was measured. We showed that the resulting mass killing of swarming males and some mate-seeking females resulted in a dramatic 80% decrease in population size compared to a control population. A significant decrease in female insemination rate and a significant shift in the age structure of the male population towards younger males incapable of mating were observed. This paradigm-shift study therefore demonstrates that targeting primarily males rather than females, can have a drastic impact on mosquito population.
Highlights
Malaria, a preventable disease, is still one of the most widespread causes of morbidity and mortality in developing countries, especially in sub Saharan Africa [1]
Targeting male mosquito swarms to control malaria vector density confirming that millions of lives have been saved by increased investments in health made over the same period [2,3,4,5,6,7,8,9]
We showed that killing males in mass as well as the few mate seeking females present in the swarms at the time of intervention significantly reduced mosquito population by as much as 80%
Summary
A preventable disease, is still one of the most widespread causes of morbidity and mortality in developing countries, especially in sub Saharan Africa [1]. Successive WHO World Malaria reports clearly indicate a significant decrease in its incidence in the past 15 years, PLOS ONE | DOI:10.1371/journal.pone.0173273. The associated mortality has decreased by 48%, from 839,000 deaths in 2000 to 438 000 in 2015 (WHO, 2015). Most malaria cases and related deaths occur in the WHO African region (88%), far ahead of the Southeast Asia region [1]. Vector control implemented mainly through Indoor Residual Spraying (IRS) campaigns and the distribution of Long-lasting insecticidal nets (LLIN) has played an important role in decreasing the incidence of the disease [10] and is typically used in combination with drug treatments
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