Frequent sugar feeding behavior by Aedes aegypti in Bamako, Mali makes them ideal candidates for control with attractive toxic sugar baits (ATSB)

Abstract

BackgroundCurrent tools and strategies are not sufficient to reliably address threats and outbreaks of arboviruses including Zika, dengue, chikungunya, and yellow fever. Hence there is a growing public health challenge to identify the best new control tools to use against the vector Aedes aegypti. In this study, we investigated Ae. aegypti sugar feeding strategies in Bamako, Mali, to determine if this species can be controlled effectively using attractive toxic sugar baits (ATSB).\n\nMethodology/Principal findingsWe determined the relative attraction of Ae. aegypti males and females to a variety of sugar sources including flowers, fruits, seedpods, and honeydew in the laboratory and using plant-baited traps in the field. Next, we observed the rhythm of blood feeding versus sugar feeding activity of Ae. aegypti in vegetation and in open areas. Finally, we studied the effectiveness of spraying vegetation with ATSB on Ae. aegypti in sugar rich (lush vegetation) and in sugar poor (sparse vegetation) urban environments.\n\nMale and female laboratory sugar feeding rates within 24 h, on 8 of 16 plants offered were over 80%. The survival rates of mosquitoes on several plant sources were nearly as long as that of controls maintained on sucrose solution. In the field, females were highly attracted to 11 of 20 sugar sources, and 8 of these were attractive to males. Peak periods of host attraction for blood-feeding and sugar feeding in open areas were nearly identical and occurred shortly after sunrise and around sunset. In shaded areas, the first sugar-seeking peak occurred between 11:30 and 12:30 while the second was from 16:30 to 17:30. In a 50-day field trial, ATSB significantly reduced mean numbers of landing / biting female Ae. aegypti in the two types of vegetation. At sugar poor sites, the mean pre-treatment catch of 20.51 females on day 14 was reduced 70-fold to 0.29 on day 50. At sugar rich sites, the mean pre-treatment catch of 32.46 females on day 14 was reduced 10-fold to a mean of 3.20 females on day 50.\n\nConclusions/SignificanceThis is the first study to show how the vector Ae. aegypti depends on environmental resources of sugar for feeding and survival. The demonstration that Ae. aegypti populations rapidly collapsed after ATSB treatment, in both sugar rich and sugar poor environments, is strong evidence that Ae. aegypti is sugar-feeding frequently. Indeed, this study clearly demonstrates that Ae. aegypti mosquitoes depend on natural sugar resources, and a promising new method for vector control, ATSB, can be highly effective in the fight against Aedes-transmitted diseases.\n\nAuthor summaryAedes aegypti are notoriously difficult to control since their ubiquitous man-made and natural breeding sites, in various geographical regions, include almost any receptacle that can hold water. These diurnal mosquitoes are anthropophilic, a preference that promotes their role as vectors of many arboviruses including Zika, dengue, chikungunya, and yellow fever. With the exception of yellow fever, there are no vaccines against any of these arboviruses so that use of personal protective measures and mosquito vector control are the only means of prevention. Disease burdens in most endemic areas are not sufficiently reduced by various integrated vector management (IVM) strategies, hence there is a need for new control tools to complement the common strategies. Control by Attractive Toxic Sugar Baits (ATSB) appears to be an ideal candidate for this purpose.\n\nThe results of this study support this proposition. They demonstrate that Ae. aegypti in their urban environments in Mali are attracted to and frequently feed on staple diet that includes a variety of flowers, fruits and seed pods. Therefore, Ae. aegypti is a suitable candidate for control with ATSB. Moreover, the experiments with ATSB, in sparse vegetation or with competitor plant attractants in rich vegetation, demonstrated that ATSB treatment can cause a drastic reduction of Ae. aegypti populations.