Entomological Component

In Mali, Benin and Nigeria, mosquitoes were collected and analysed to determine which vector species were present and whether they were infected with the malaria parasite. Research conducted included:

• Mosquito collection in human dwellings using pryrethrum spray catches (PSC) and WT methods;

• Phenotypic and genotypic profiling of malaria vectors in selected sites.

Additional activities were also conducted in some study sites, such as:

• Experimental hut trials of the effect of developed insecticide resistance on entomological indices of malaria transmission; and

• High performance liquid chromatography (HPLC) analysis of insecticide residues in net fibers (a laboratory technique) during the study period.

• An. gambiae s.l. was the predominant malaria vector present in the mosquito catches. Very few An. funestus were reported in some localities.

• The resistance level had recently increased across localities, including in the presumed susceptible locality. Thus, no site susceptible to pyrethroids was found.

• Vector populations in all sites were fully susceptible to the organophosphates (pyrimiphos-methyl) currently used for IRS in Mali.

• Except for human blood index, all entomological transmission indices (including vector density per house, biting and infection rates) were lower in indoor residual spraying (IRS) sites compared to those without IRS.

• Transmission as measured by entomological inoculation rate (EIR) was undetectable in IRS sites, while it was still high in areas without IRS. This demonstrates a recurring issue: limited access to LLINs and no clear policy to replace worn or damaged nets.

• It was unknown when and how often IRS was carried out.

• Baseline entomological data revealed Anopheles gambiae s.s. as the major Anopheles species in the four villages, representing more than 90% of the Anopheles population at each site.

• Mosquito indoor density was similar at the four sites, ranging between nine and 13 mosquitoes per room per day.

• LLINs were distributed to the inhabitants of the four villages according to the Nigerian national guideline of two LLINs per household.

• Entomological results generated from activities conducted in Benin revealed that mosquitoes (An. gambiae and An. funestus) from most surveyed sites were found resistant to pyrethroid insecticides used in malaria vector control measures in Benin (multiple insecticide resistance, both metabolic and target site mutations).

• The level and intensity of resistance varied from the north to the south, with higher resistance recorded in the south.

• Data from experimental hut trials conducted at this site revealed higher transmission risk with released resistant mosquitoes (compared to susceptible mosquitoes) for individuals sleeping in huts and protected by treated nets (LLINs).

• In the two selected study sites, it was found that there was higher resistance to pyrethroids in Kpome than in Ketonou.

• Results from experimental huts and from households revealed that malaria transmission indices (entomological surveys) were higher as the resistance levels of mosquitoes increased.

• Low presence of insecticide residues in LLINs used by identified malaria patients was recorded, in comparison to those without malaria, whose nets had more insecticides.