Decreased proportions of indoor feeding and endophily in Anopheles gambiae s.l. populations following the indoor residual spraying and insecticide-treated net interventions in Benin (West Africa)

Abstract

BackgroundIn many parts of Africa as in Benin, the main strategies of vector control are based on the scaling-up of Long Lasting Insecticide Treated Nets (LLITNs) and indoor residual spraying (IRS). The need to understand the biological implications of IRS in large scale and full coverage of LLITNs is paramount. It is in this context that the present study was conducted. It aims to evaluate the effect of a large scale IRS using a non-pyrethroid insecticide and full coverage of deltamethrin treated nets on the behavior of An. gambiae s.l. in the intervention areas compared to untreated areas used as controls.MethodsMosquitoes were collected using human landing catches, pyrethrum spray catches and window exit traps to assess reduction of entry rate, endophily rate, endophagy rate and overall mortality rate in natural populations of An. gambiae s.l. before IRS and LLITNs intervention (2007) and after in 2008 and 2010.ResultsIn the IRS arm, endophily rate was 67.13% before intervention and 4.5% after intervention, whereas in the control arm it was stable at 51.67% (P > 0 .05). In the LLITN arm endophily rates also decreased after intervention. After the IRS, no gravid mosquitoes were collected from all treated localities, but LLITN performance was not that spectacular. The proportion of mosquitoes biting indoors in the IRS arm decreased from 67.09% before intervention to 42.85% after intervention, compared to a low but significant decrease (71.31% to 57. 46%) in the LLITN arm.The use of vector control tools and behavior of the host would be the main factors that modify the behavior of taking a human blood meal observed on An. gambiae s.l. inside human dwellings.ConclusionThe impact on the behavior of An. gambiae s.l. observed with the bendiocarb used in IRS was highly effective compared with the free distribution of LLITNs in terms of mortality and the decrease of proportions of indoor feeding. Despite this efficacy, there is a need for complementary tools and research of alternative strategy oriented on effective health education, and the use of powerful tools such as IRS, LLITNs, larviciding and repellents.

Blood feeding behaviour comparison and contribution of Anopheles coluzzii and Anopheles gambiae, two sibling species living in sympatry, to malaria transmission in Alibori and Donga region, northern Benin, West Africa

“…coluzzii and An. gambiae collected indoors were blood-fed with a high and similar anthropophagic index (0.97), mirrors results from similar studies [17, 19–23]. As a result of both species having similar attractions to humans, An.…”

The Impact of Periodic Distribution Campaigns of Long-Lasting Insecticidal-Treated Bed Nets on Malaria Vector Dynamics and Human Exposure in Dielmo, Senegal

“…In addition, the behavioral changes of vector and the shift in species composition resulting from the use of LLINs may also compromise the efficacy of malaria control tools. [18][19][20][21][22][23][24] Indeed, the strategy to use LLINs is mainly effective against those malaria vectors that are mostly anthropophilic, and bite and rest inside rooms. 25 These are the distinctive characteristics of the main African malaria vectors that belong to the Anopheles gambiae complex and the Anopheles funestus group.…”

Entomological and parasitological impacts of indoor residual spraying with DDT, alphacypermethrin and deltamethrin in the western foothill area of Madagascar

“…Although, even with correct implementation, IRS with insecticide did not eliminate malaria transmission. This has been observed on many similar occasions [4,11,19,20,26,32]. The persistence of malaria vectors, with or without malaria cases, following an effective vector control measure is a known phenomenon since the 1960s [48].…”

“…New tools were suggested for reducing malaria transmission, but nevertheless, chemical insecticides are still essential [17,18], and in most malaria-endemic countries, especially sub-Saharan Africa, IRS remains an important method of fighting endophilic malaria vectors [19,20]. …”