Key Findings
Key findings: Mali
Malaria vectors in Mali showed widespread and increasing resistance to insecticides, especially pyrethroids; multiple resistance mechanisms were recorded in studied localities.
The effect of resistance on the performance of long-lasting insecticidal nets (LLINs) was recorded; however, organophosphate-based indoor residual spraying (IRS) introduction in some study sites seemed to moderate the negative effect of the above-described resistance phenomenon. Vector populations remained susceptible to the organophosphate-based class of insecticide.
A good insecticide resistance management and implementation plan should be developed.
Education regarding the causes and risks of malaria and the usage of LLINs should be increased.
Key findings: Nigeria
Anopheles gambiae s.s. was the main Anopheles species, constituting 80–100% of the Anopheles population in the different villages.
LLIN coverage in Ikorodu was low, with the socio-anthropological data revealing that LLIN use was not common in the four villages. Less than 20% of households surveyed owned a net.
LLIN coverage in the four villages was low prior to net distributions due to non-availability of LLINs in the market.
Sleeping under LLINs greatly reduced the number of mosquito bites a person received.
In areas where mosquitoes had metabolic resistance, net ineffectiveness was shown by mosquito bites received while sleeping under LLINs, and by the presence of live mosquitoes hanging onto LLINs.
In Nigeria, less than 20% of households surveyed owned a net.
Key findings: Benin
Mosquitoes (An. gambiae and An. funestus) from most surveyed sites were found to be resistant to the pyrethroid insecticides used as malaria vector control measures.
The level of insecticide resistance varied from the north to the south of Benin, with higher resistance recorded in the south.
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) increased with the resistance levels of the mosquitoes.
Although the number of malaria cases was almost similar in both localities, more severe malaria cases were recorded in Kpome, the locality with a higher resistance level.
Despite high net coverage (>75%) recorded in both study sites, malaria cases were still recorded in several households, which could have been due to:
The high resistance level of mosquitoes to insecticides (multiple insecticide resistance mechanisms, both metabolic and target mutations);
The reduction of insecticide residues in net fibres as a result of net washing practices; and
The poor sleeping behaviours of net users, as some net users' hands and limbs were in contact with nets while they were sleeping.