Combined use of long-lasting insecticidal nets and Bacillus thuringiensis israelensis larviciding, a promising integrated approach against malaria transmission in northern Côte d’Ivoire.

Background The recent reduction in malaria burden in Côte d’Ivoire is largely attributable to the use of long-lasting insecticidal nets (LLINs). However, this progress is threatened by insecticide resistance and behavioral changes in Anopheles gambiae sensu lato (s.l.) populations and residual malaria transmission, and complementary tools are required. Thus, this study aimed to assess the efcacy of the combined use of LLINs and Bacillus thuringiensis israelensis (Bti), in comparison with LLINs. Methods This study was conducted in the health district of Korhogo, northern Côte d’Ivoire, within two study arms (LLIN+Bti arm and LLIN-only arm) from March 2019 to February 2020. In the LLIN+Bti arm, Anopheles larval habi‑ tats were treated every fortnight with Bti in addition to the use of LLINs. Mosquito larvae and adults were sampled and identifed morphologically to genus and species using standard methods. The members of the An. gambiae complex were determined using a polymerase chain reaction technique. Plasmodium infection in An. gambiae s.l. and malaria incidence in local people was also assessed. Results Overall, Anopheles spp. larval density was lower in the LLIN+Bti arm 0.61 [95% CI 0.41–0.81] larva/dip (l/dip) compared with the LLIN-only arm 3.97 [95% CI 3.56–4.38] l/dip (RR=6.50; 95% CI 5.81–7.29; P<0.001). The overall bit‑ ing rate of An. gambiae s.l. was 0.59 [95% CI 0.43–0.75] biting/person/night in the LLIN+Bti arm against 2.97 [95% CI 2.02–3.93] biting/person/night in LLIN-only arm (P<0.001). Anopheles gambiae s.l. was predominantly identifed as An. gambiae sensu stricto (s.s.) (95.1%, n=293), followed by Anopheles coluzzii (4.9%; n=15). The human-blood index was 80.5% (n=389) in study area. EIR was 1.36 infected bites/person/year (ib/p/y) in the LLIN+Bti arm against 47.71 ib/p/y in the LLIN-only arm. Malaria incidence dramatically declined from 291.8‰ (n=765) to 111.4‰ (n=292) in LLIN+Bti arm (P<0.001). Conclusions The combined use of LLINs with Bti signifcantly reduced the incidence of malaria. The LLINs and Bti duo could be a promising integrated approach for efective vector control of An. gambiae for elimination of malaria. [ABSTRACT FROM AUTHOR]