Vol. 9, Issue 2, Part A (2022)

The different methods used for the control of An. gambiae s.l. have led to the deployment of several defensive weapons by these vectors. Indoor residual spraying (IRS) implemented annually in the northern part of the country, and the national distribution of long-lasting insecticide-treated nets (LLINs) carried out every 3 years are the main malaria vector control tools deployed by the NMCP. The toxicity of insecticides in these tools results from their interaction with their biological target in the insect. Thus, for the effectiveness of vector control tools in an area, the knowledge of different defense weapons of Anopheles present in the area is essential.

The characterization of resistance mechanisms present on samples of pyrethroid-resistant Anopheles gambiae s.l. was carried out in four districts of northern Benin taking into account the different agricultural production zones. The different species, resistance gene and enzyme present in these districts were investigated.

High resistance of Anopheles gambiae s.l. in the four communes was observed, surviving a high frequency of the kdr resistance gene. Mosquito mortality rates ranged from 56.80% (95% CI: 50.51 - 62.95) in Kandi, to 70.24% (95% CI: 64.61 - 75.45) in N'Dali with deltamethrin, from 57.14% (95% CI: 51.04 - 63.09) in Kandi, to 74.80% (95% CI: 68.94 - 80.06) in N'Dali with permethrin, and from 59.63% (95% CI: 51.76 - 67.17) in Kandi, to 72.90% (95% CI: 66.24 - 78.89) in Parakou with alphacypermethrin. The lowest frequency of the kdr gene was observed in An. coluzzii 64.00% (95% CI: 56.90 - 70.60) in Malanville and the highest frequency in Kandi in An. gambiae 88.33% (95% CI: (82.70 - 92.60). It should also be noted that An. gambiae s.l. from these four districts also use detoxification enzymes to eliminate pyrethroid toxicity. These are: the communes of Parakou, Kandi and N'Dali for α and β esterases (pα < 0.05 and pβ < 0.05), Kandi, Malanville and N'Dali (p< 0.0001) for mixed function oxidases (MFOs), and the communes of Parakou, Kandi and N'Dali for glutathione-S-transferase (GST) activities (p< 0.05).

Three species of An. gambiae s.l. are collected in the communes and in all the agricultural production areas studied with a strong involvement of several resistance mechanisms (L1014F kdr, MFOs, Esterases and GST).