Susceptibility of Anopheles gambiae Sl to the Insecticides in Praia, Cape Verde: A Country in the Pre-Elimination of Malaria

Background: Success for malaria control and elimination implies effective vector control strategies. In Cape Verde, country in the pre-elimination phase of malaria, the Indoor Residual Spraying with insecticides is the main strategy in the vector control. The objective of this study was to assess the level of insecticide sensitivity of Anopheles gambiae sensu lato, populations from Praia, Cabo Verde, to the principal insecticide recommended for IRS, the deltamethrine 0.05%, 0.25% and 0.5%, Bendiocarb 1% and malatahion 5%.

Methods: Larvae of Anopheles gambiae s.l were collected from different sites in Praia and reared to adult stages in the medical entomology lab. The sensibility/resistance status was assessed using the WHO bioassay test kits for adult mosquitoes. The result of studies was analysed, determining the mortality rate for different insecticide, the KD determined with Log-Probit and others data analysis with Excel. Results: A total of 693 females of An. gambiae s.l. was used to determine the sensitivity status. The results of demonstrating an increase of KDR times more pronounced with the lowest concentration of deltamethrin (0.05%), compared to the highest concentrations (0.25% and 0.5%). We found a resistance to deltamethrin 0.05% and Malathion 5%, although less marked with mortality rates above 80%. However, the vector population were found completely susceptible to deltamethrin 0.25%, deltamethrin 0.5% and to bendiocarb 1%.

Conclusion: This study provides updated information about the sensibility of An. gambiae s.l. to insecticides in Praia, Cape Verde. The constant use of this insecticides, for long years, in vector control as well in agriculture, could be the cause to the selection pressure for resistance. We recommend the use of this findings in the definition of the vector control strategies and to the implementation of a routine resistance monitoring to the malaria vector control in the country.