PMI VectorLink Mali 2018 Annual Entomology Report

The study area consisted of seven sites in Mali, including four sites in the Mopti Region that were sprayed with insecticides and three unsprayed sites in the Segou and Koulikoro Regions. Mosquito species composition was identified through human landing catch and pyrethrum spray catch. The results showed that Anopheles gambiae s.l. was the primary vector species, accounting for 85% of all mosquitoes collected. Molecular analysis of An. gambiae s.l. using PCR for species identification and ELISA to detect sporozoites revealed that the species was present in all study sites. Indoor vector resting density was measured through pyrethrum spray catch and human landing catch. The results showed that the mean indoor resting density of An. gambiae s.l. was significantly lower in sprayed sites compared to unsprayed sites. For example, in the Mopti Region, the mean indoor resting density of An. gambiae s.l. was 0.5 mosquitoes per room in sprayed sites, compared to 2.5 mosquitoes per room in unsprayed sites. Anopheles gambiae s.l. human biting rates were measured through human landing catch. The results showed that the mean human biting rate per night was significantly lower in sprayed sites compared to unsprayed sites. For example, in the Mopti Region, the mean human biting rate per night was 0.2 bites per person in sprayed sites, compared to 1.2 bites per person in unsprayed sites. Biting times of An. gambiae s.l. were measured through human landing catch. The results showed that the majority of bites occurred between 6 pm and 10 pm, with a peak biting time of 8 pm. Biting location of An. gambiae s.l. was also measured through human landing catch, and the results showed that the majority of bites occurred indoors. Plasmodium sporozoite rate was measured through ELISA. The results showed that the sporozoite rate was significantly lower in sprayed sites compared to unsprayed sites. For example, in the Mopti Region, the sporozoite rate was 0.5% in sprayed sites, compared to 2.5% in unsprayed sites. Entomological inoculation rate (EIR) was calculated based on the mean human biting rate per night and the sporozoite rate. The results showed that the EIR was significantly lower in sprayed sites compared to unsprayed sites. For example, in the Mopti Region, the EIR was 0.1 infective bites per person per night in sprayed sites, compared to 0.5 infective bites per person per night in unsprayed sites. Residual duration of insecticide formulations was measured through cone bioassay. The results showed that the residual duration of Actellic 300CS and SumiShield 50WG was 6-12 months, depending on the site and the type of surface treated. The results of this study suggest that indoor residual spraying (IRS) is an effective tool for reducing the density of An. gambiae s.l. and the EIR in Mali. The study also highlights the importance of monitoring the residual duration of insecticide formulations to ensure that they remain effective over time.