High Malaria transmission risk in Burkina Faso village despite bednets coverage

Long lasting insecticide treated bednets (LLINs) are considered by WHO among the most effective strategies in malaria control [1]; nevertheless, their impact in Africa seems to be heterogeneous, since in some hyperendemic countries (where LLIN coverage reached 70%) the malaria incidence and the entomological infection rates are still very high [2]. We assessed the risk of malaria transmission in Goden, a LLIN-protected village of Burkina Faso, where in a previous survey (2011) [3] it has been detected a high proportion of Plasmodium infective mosquitoes (7.1%). Host-seeking mosquitoes were sampled indoors and outdoors at three-night time points in November 2015 by Human Landing Catch. A total of 1996 Anopheles gambiae complex specimens was collected (A. coluzzii 55%, A. arabiensis 44%, A. gambiae 1%, with no significant differences in time and position) corresponding to a median number of 23.5 mosquitoes/hour/person. Among these 5.8% were Plasmodium infective with a rate of 1.4 infective bites/person/hour (9.5 per night), both inside and outside houses. Moreover, a high frequency of insecticide resistance was detected in sampled mosquitoes both indoors and outdoors (kdr allele 54%; N=298). These results confirm that, despite the use of LLINs in the village from several years, mosquito population is still highly infected. The high vector density, biting behavior and insecticide resistance, lead to a non-negligible risk of malaria transmission both to people unprotected by a bednet indoors and to those exposed outdoors. This suggest that LLINs, although effective for personal protection, do not significantly reduce the transmission risk at population level. References