Responses of mosquitoes to insecticide-treated and untreated bed-net trap
We tested the individual response of resistant and susceptible mosquitoes to a human host sleeping under either an insecticide-treated or untreated net in the hut in the MalariaSphere. In 30 experimental nights (i.e. 15 treated and 15 untreated test repeats) out of 12,000 female An. gambiae s.s mosquitoes released, 55.5% (95% CI= [54.7-56.4]) were recovered. A total of 2879 (43.2%) female mosquitoes were caught in the bed net traps out of 6665 mosquitoes recaptured. The proportion of resistant females caught in the treated bed net trap was higher than that of the susceptible females(43 vs 28.3% OR=1.445; 95% CI=[1.25-1.68]; P<0.0001, Fig.3), indicating that the resistant population was 1.4 times more likely to seek a host in the presence of a treated net than the susceptible population. When an untreated bed net trap was erected, the proportion of resistant females (51.1% ,95% CI= [48.7-53.5]) caught in the bed net trap did not differ with that of the susceptible population 51.3% (95% CI=[48.8-53.6]) (OR=0.95; 95% CI=[0.86-1.04]; P>0.05).When the untreated net was present the susceptible mosquitoes were 2.7 times more likely to search for a host than when a treated bed net was present (OR=2.65; 95% CI=[2.29-3.05]; P<0.0001, Fig 3).Overall, there was a significant effect of treatment type on mosquito host-seeking behavior, with more mosquitoes caught in the bed net trap when untreated net was present than when there was a treated bed net trap (OR=1.908; 95% CI=[1.73-2.12]; P< 0.0001,Fig. 3).
For the wild population, a total of 1013 (50.6%) mosquitoes were recaptured out of 2000 F1 females released. The proportion of the wild population caught in the untreated bed net trap was slightly higher 40% compared to treated bed net trap 33.5% (Fig. 3). Although, this was not statistically significant (OR=0.773; 95% CI=[0.598-0.999]; P=0.489). The mortality of the resistant population trapped in the treated bed net trap was 77.7 % (549/706) and 85. 2% (144/169) for the wild population. All the susceptible mosquitoes trapped in the insecticide-treated bed net were dead.