Contribution of larviciding with biological compounds to the management of pyrethroid resistance in a highly resistant population of Anopheles coluzzii the major malaria vector in Cameroon.
1
University of Yaoundé I, Yaoundé, Cameroon
2
OCEAC, Yaoundé, Cameroon
Popul. Med. 2026;8(Supplement Supplement 1):
ABSTRACT
ABSTRACT:
Larviciding using non-insecticide compounds is considered appropriate for controlling outdoor biting mosquitoes and for managing insecticide resistance. However, the influence of larviciding in managing pyrethroid resistance remains unexplored. We investigated whether larviciding using the microbial-based larvicide VectoMax G is contributing to increase the susceptibility of Anopheles coluzzii populations to pyrethroids. Therefore, the susceptibility status of Anopheles coluzzii field population was evaluated at different time points, before and during larviciding treatments. Simultaneously, Anopheles coluzzii larvae were collected and splited into four groups, each subjected to 21 generations of selection, as follows; (i):deltamethrin0.05%_only, (ii):VectoMax_only, (iii):VectoMax+deltamethrin0.05%, (iv):VectoMax+deltamethrin0.05%+susceptible. Life-traits parameters were measured in the progeny. Kdr frequency, then expression profile of detoxification and oxidative genes was checked using qPCR. Phenotypic and genotypic parameters were compared between the first and the last generation of each laboratory colony and between field samples collected before and during larviciding, with “Ngousso” strain as control. First findings shown a decrease in resistance intensity to deltamethrin from high to low in field populations. Overall, the colony vectomax+deltametrin+susceptible displayed a fitness profile similar to the susceptible colony, with short development time and long adult survival rate. Moreover, the kdr gene frequency was found to be unchanged in the field population and laboratory colonies and a significant decrease in the overexpression profile of detoxification genes was detected in field population after larviciding implementation. The study suggests that, under larvicide treatment, resistance reversal is possible, but it may take longer to establish in a population expressing a very high resistance profile and subject to continuous insecticide selection pressure. Furthermore, the addition of new tools specifically targeting the larval stages could improve malaria vector control and insecticide resistance management.
Larviciding using non-insecticide compounds is considered appropriate for controlling outdoor biting mosquitoes and for managing insecticide resistance. However, the influence of larviciding in managing pyrethroid resistance remains unexplored. We investigated whether larviciding using the microbial-based larvicide VectoMax G is contributing to increase the susceptibility of Anopheles coluzzii populations to pyrethroids. Therefore, the susceptibility status of Anopheles coluzzii field population was evaluated at different time points, before and during larviciding treatments. Simultaneously, Anopheles coluzzii larvae were collected and splited into four groups, each subjected to 21 generations of selection, as follows; (i):deltamethrin0.05%_only, (ii):VectoMax_only, (iii):VectoMax+deltamethrin0.05%, (iv):VectoMax+deltamethrin0.05%+susceptible. Life-traits parameters were measured in the progeny. Kdr frequency, then expression profile of detoxification and oxidative genes was checked using qPCR. Phenotypic and genotypic parameters were compared between the first and the last generation of each laboratory colony and between field samples collected before and during larviciding, with “Ngousso” strain as control. First findings shown a decrease in resistance intensity to deltamethrin from high to low in field populations. Overall, the colony vectomax+deltametrin+susceptible displayed a fitness profile similar to the susceptible colony, with short development time and long adult survival rate. Moreover, the kdr gene frequency was found to be unchanged in the field population and laboratory colonies and a significant decrease in the overexpression profile of detoxification genes was detected in field population after larviciding implementation. The study suggests that, under larvicide treatment, resistance reversal is possible, but it may take longer to establish in a population expressing a very high resistance profile and subject to continuous insecticide selection pressure. Furthermore, the addition of new tools specifically targeting the larval stages could improve malaria vector control and insecticide resistance management.
| eISSN: | 2654-1459 |
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