Background: To overcome the spread of high pyrethroid resistance in the main malaria vectors and malaria disease persistence, it is crucial to look for effective and better resistance management strategies. Understanding the phenotypic profile of Anopheles gambiae sl. against alternatives insecticides like organophosphates and carbamates is crucial.
Methods: Anopheles larvae and pupae were collected from the breeding sites in rice fields, pineapple crop areas, and peri-urban areas. WHO susceptibility tests were conducted on unfed female mosquitoes aged 3-5 days old. Mosquitoes were exposed to malathion 5%, pirimiphos-methyl 0.25%, and bendiocarb 0.1% using the standard WHO protocol. Polymerase chain reaction (PCR) techniques were used to detect species, kdr and Ace-1 mutations.
Results: Anopheles gambiae sl. from Sèdjè-Dénou rice field population was resistant to bendiocarb (0.1%) with a mortality rate of 72.2% whereas Anopheles gambiae sl. populations from Zinvié-Dokomey (rice field), Zè-Tozounmè (pineapple field), and Adjagbo (peri-urban area) were suspected to be resistant with mortality rates of 90%, 93.5%, 95.4% respectively. However, all of them were susceptible to organophosphates (malathion and pirimiphos-methyl) with a mortality rate of 100%. PCR assay revealed that 100% of the mosquitoes tested were Anopheles coluzzii. The frequencies of Ace-1R mutation in all Anopheles coluzzii populations tested were low (3-27%).
Conclusions: Organophosphates (malathion and pirimiphos-methyl) have maintained their efficacy against Anopheles coluzzii populations from Sèdjè-Dénou (rice field), Zè Tozounmè (pineapple field), Zinvié Dokomey (rice field), or Adjagbo (peri-urban area). The good efficacy of these organophosphates against Anopheles coluzzii populations from the southern part of Benin are observed in the current study. The use of pirimiphos-methyl for IRS in this part of the country would be a successful alternative for malaria control in this area.
Keywords: Anopheles coluzzii; Benin; bendiocarb; insecticides resistance; malathion; pineapple field; pirimiphos-methyl; rice field.
To better manage the spread of high pyrethroid resistance in malaria-carrying mosquitoes, we need to find effective solutions. To do this, we need to understand how these mosquitoes react to different insecticides. We collected Anopheles larvae and pupae from different breeding sites and tested them using WHO susceptibility tests. We used malathion, pirimiphos-methyl, and bendiocarb to see how the mosquitoes reacted. We found that Anopheles gambiae sl. mosquitoes from different areas had different levels of resistance to bendiocarb. From one of the site, mosquitoes were found resistant, with a mortality rate of 72.2%, while populations from other areas had mortality rates of 90%, 93.5%, and 95.4%, respectively. However, all populations were susceptible to malathion and pirimiphos-methyl. We also used PCR assays to identify the species and mutations present. We found that all of the mosquitoes tested were Anopheles coluzzii, and that the mutations present were rare. Our study found that malathion and pirimiphos-methyl are effective against Anopheles coluzzii populations in different areas. We suggest using pirimiphos-methyl as a successful alternative for malaria control in this part of the country.
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