Anopheles arabiensis and Anopheles funestus biting patterns in Dielmo, an area of low level exposure to malaria vectors


Background In Dielmo, Senegal, the widespread use of long-lasting insecticidal nets has decreased both the incidence of malaria and the density of theAnophelespopulation. However, persistent low-level malaria transmission may hamper efforts to eliminate the disease. Therefore, continuous monitoring of the vector population is needed in order to improve knowledge ofAnophelesbiting behaviour and to readjust control interventions. Methods In 2015,Anopheleswere collected every month for a whole year and each specimen was identified using morphological and molecular techniques. The biting pattern of each species was analysed according to night (7 pm-7am) and morning (7am-11am) periods, the place of biting and the season. The ELISA CSP technique was used to assess thePlasmodium falciparumsporozoite rate to evaluate the entomological inoculation rate (EIR). Results Anopheles arabiensisandAnopheles funestussensu stricto were found to be the main vectors biting humans. Overall, the biting rate was low, at 3.84bites per night (bpn) and 1.27 bites per morning (bpm), respectively (IRR = 3.04, CI [1.84-5.00], p < 0.001). The EIR was 2.51 and 5.03 infectious bites per year during the night and morning, respectively. During the night, theAn. arabiensisandAn. funestusbiting rate was 1.81 bpn and 1.71 bpn, respectively (IRR = 0.95, CI [0.46-1.92], p = 0.88). During the morning, their density decreased to 0.51 bpm and 0.73 bpm forAn. arabiensisandAn. funestus, respectively (IRR = 1.47, CI [0.58-3.71], p = 0.41). During the night and the morning, no specific trend of indoor or outdoor biting was observed in the dry and rainy season for both vectors. Conclusion This study highlighted low levelAnophelesnocturnal and diurnal biting and the associated risk of malaria transmission. It showed also the influence of the season on the indoor and outdoor biting pattern, indicating that the human population could be exposed all year round to a low level ofAnophelesbites. Control programmes should increase awareness of the use of bed nets throughout the year and promote the development and implementation of complimentary tools to targetAnophelesbiting shortly after dawn when people are still indoors and outside the bed nets

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Horizon / Pleins textes

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This paper was published in Horizon / Pleins textes.

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