Impact of Long-Lasting Insecticidal Nets and Indoor Residual Sprayings on Susceptibility of Anopheles gambiae (Diptera: Culicidae) in Western Côte d'Ivoire

Pyrethroid insecticides resistance in several Anopheles species represents a threat for the success of malaria vector control based on using treated nets and indoor sprayings. Impact of the long-lasting insecticidal net (LLIN) of Permanet type and indoor residual spraying (IRS) with deltamethrin on the levels of susceptibility to pyrethroids and DDT were investigated in field populations of Anopheles gambiae in 12 villages located in the Danane area in Western Cote d'Ivoire. From May 2001 to July 2002, adult An. gambiae reared from larvae collected from these villages were tested with 0.05% deltamethrin, 1% permethrin, and 4% DDT impregnated papers using WHO standard test kits. Knockdown times for 50% of adult mosquitoes (kdT50) of field specimens from LLINs, untreated nets, IRS, and control villages significantly differed from those of the Kisumu susceptible strain. However, the resistance ratios of the kdT50 were very low. KdT50 did not significantly differ with all treatments, chemicals (LLINs and IRS), physical (untreated nets), and control. The mortalities were above 80% indicating susceptible populations of An. gambiae in the Danane area. There was no significant difference between mortality rates from the different treatments.