Foraging behavior of the malaria vector Anopheles arabiensis following introduction of insecticide treated bed nets in southern Zambia

Anopheles arabiensis is the primary mosquito vector responsible for Plasmodium falciparum transmission in Macha, Zambia. Since insecticide treated bed nets (ITNs) have the potential to alter host feeding behavior, the extent of the vector’s zoophilic and exophagic tendencies was evaluated during the two rainy seasons following ITN introduction. Paired indoor/outdoor human landing catches (HLCs) and outdoor cattle-baited collections were used to assess potential changes in host preference. Results support the hypothesis that An. arabiensis in Macha remains highly anthropophilic despite high ITN use. Additionally, HLCs and Centers for Disease Control light traps were employed to determine if ITNs were having an effect on foraging behavior. Similar numbers of mosquitoes were caught in light traps hung next to treated and untreated bed nets, suggesting that ITNs have little effect on entering behavior. Although no repellant effect was observed, An. arabiensis in Macha appears to be relatively exophagic and has been caught biting outdoors both right after sunset and right before sunrise, potentially circumventing the protective effects of ITNs. Despite the lack of repellency, microsatellite analysis of human blood meals in An. arabiensis has revealed that the number of multiple-person blood meals has dropped from over 20% to nearly 8% with the introductions of ITNs. This may suggest that ITNs have reduced the number of people accessible to these vectors, but those individuals that are exposed may be at higher risk for malaria transmission.