Beyond nature and nurture: phenotypic plasticity in blood-feeding behavior of Anopheles gambiae s.s. when humans are not readily accessible.

To test for the effects of host accessibility on blood-feeding behavior, we assessed degrees of anthropophily of the malaria mosquito Anopheles gambiae at two stages of the behavioral sequence of host foraging, in a rice growing area near Bobo-Dioulasso, Burkina Faso, where humans are not readily accessible because of years of generalized use of (mostly non-impregnated) bed nets. First, patterns of host selection were assessed by the identification of the blood meal origin of indoor-resting samples. Inherent host preferences were then determined by two odor-baited entry traps, set side by side in a choice arrangement, releasing either human or calf odor. The proportion of feeds taken on humans was around 40%, whereas 88% of trapped An. gambiae "chose" the human-baited trap, indicating a zoophilic pattern of host selection despite a stronger trap entry response with human odor. This paradox can be interpreted as the evolution of a plastic strategy of feeding behavior in this field population of An. gambiae because of the greater accessibility of readily available, although less-preferred, hosts.