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.