Behavioral responses of pyrethroid-resistant Anopheles gambiae
mosquitoes to insecticide-treated bed net
Abstract
Long-lasting insecticidal nets are an effective tool in reducing malaria
transmission. However, with increasing insecticide resistance little is
known about how physiologically resistant malaria vectors behave around
a human-occupied bed net, despite their importance in malaria
transmission. This study assessed the host-seeking behavior of the major
malaria vector Anopheles gambiae s.s, when an intact human-occupied
treated bed net is in place, with respect to their insecticide
resistance status under semi-field conditions. Pyrethroid resistant and
susceptible females of Anopheles gambiae s.s were released inside a
semi-field environment housing a hut which was occupied by a human host
sleeping under treated or untreated bed net trap. Mosquitoes resting
inside the hut or exiting and resting outside were collected using a
prokopack aspirator, window exit trap and clay pots. The proportion of
resistant females caught in the treated bed net trap was higher compared
to the susceptible females (OR=1.445; P<0.00019). Resistant
mosquitoes were less likely to exit the house when a treated bed net was
present compared to the susceptible mosquitoes. The susceptible females
were 2.3 times more likely to stay outdoors away from the treated bed
net (OR=2.25; P<0.0001).The resistant mosquitoes showed
significantly reduced avoidance behavior compared to the susceptible
mosquitoes that were observed to exit the house and remained outdoors
when a treated bed net was used. However, further investigations of the
behavior of resistant mosquitoes under natural conditions should be
undertaken to confirm these observations and improve the current
intervention which are threatened by insecticide resistance and altered
vector behavior.