First detection of F1534C knockdown resistance mutation in Aedes aegypti (Diptera: Culicidae) from Cameroon

Abstract

Background Aedes borne viral diseases, notably dengue, are increasingly reported in Cameroon with Aedes aegypti being a major vector. Data on insecticide resistance of this vector and underlying mechanisms needed for outbreak preparedness remain scarce in Cameroon. Here, we present the nationwide distribution of insecticide resistance in Ae. aegypti and investigate the potential resistance mechanisms involved. Methods Immature stages of Ae. aegypti were collected between March and July 2017 in 13 locations across Cameroon and reared until G1/G2/G3 generation. Larval, adult bioassays, and piperonyl butoxide (PBO) synergist assays were carried out according to World Health Organization guidelines. F1534C mutation was genotyped using allele specific polymerase chain reaction in field collected adults (Go) and the polymorphism of the sodium channel gene was assessed. The χ2 test was used to compare the mortality rate between bioassays with insecticides only and bioassays after preexposure to PBO synergist. Results Larval bioassay revealed that all the three populations tested with temephos were susceptible. Adult bioassays showed a good level of susceptibility toward both pyrethroids tested, 0.25% permethrin and 0.05% deltamethrin, with six out of 10 populations susceptible. However, two populations (Douala and Edéa) were resistant (deltamethrin [73.2–92.5% mortality], permethrin [2.6–76.3% mortality]). The resistance to 4% dichlorodiphenyltrichloroethane was observed in four out of 10 populations tested (16.8–87.1% mortality). Resistance was also reported to carbamates including 0.1% propoxur (60.8–87.1% mortality) and to 0.1% bendiocarb (82.9% mortality). All populations tested were fully susceptible to 1% fenitrothion. A partial recovery of susceptibility was observed in the pyrethroid resistant population of Douala after pre-exposed to PBO suggesting the implication of cytochrome P450 monoxygenases permethrin resistance. Genotyping and sequencing detected the F1534C kdr mutation in the two pyrethroid resistant locations of Edéa and Douala, with allelic frequency of 3.3% and 33.3% respectively. However, the high genetic diversity of the sodium channel gene supports the recent introduction of this mutation in Cameroon. Conclusions This study revealed the contrasting resistance profiles to insecticides of Ae. aegypti populations in Cameroon suggesting that, instead of a unique nationwide control approach, a regionally adapted strategy will be needed to control this vector. The localised distribution of the F1534C kdr mutation supports this region-specific control strategy.

Temporal Evaluation of Insecticide Resistance in Populations of the Major Arboviral Vector Aedes Aegypti from Northern Nigeria

“…aegypti, where the resistance correlates with the presence of V1016G mutation [42,43]. Recently, Yougang and colleagues [44] reported for the first time F1534C mutation and contrasting patterns of resistance to all the four classes of insecticides in Cameroon and implicated the F1534C mutation in resistance to the pyrethroids and DDT. Previous reports from Cameroon, Burkina Faso and Congo also revealed different patterns of resistance to pyrethroids and DDT, with partial restoration of resistance after pre-exposure to synergists, diethylmaleate and piperonylbutoxide [44][45][46][47][48].…”

First Evidence of the Implication of Cuticular Based Mechanisms in Aedes Aegypti Populations Resistant To Pyrethroids and DDT in Cameroon

“…Although the present study did not measure cuticular thickness (thickness of procuticle and/or epicuticle), it is possible that resistant mosquitoes with enriched CHCs could display a thicker epicuticle, but needs further investigation. Cuticular resistance mechanisms alongside with target site and metabolic based mechanisms recently detected in Aedes aegypti from Cameroon [9,11], could further increase the complexity of insecticide resistance pattern in Aedes aegypti and warrants further investigation…”

“…Three kdr mutations including F1534C, V1016G and V1016I associated with resistant phenotypes were recently recorded in Ae. aegypti [9,11]. The kdr allele F1534C was also recorded in Ae.…”

“…aegypti and Ae. albopictus [9][10][11][12]. Yet, despite the fact that these two species share similar habitats and are most of the time recorded in sympatry, resistance seems to expand more rapidly in Ae.…”

Insecticide susceptibility of Aedes (Stegomyia) aegypti (Linnaeus, 1762) and Aedes (Stegomyia) albopictus (Skuse, 1894) in Kinshasa, Democratic Republic of the Congo

“…More than 10 mutations have been recorded globally, of which the F1534C, V1016I, and V410L mutations have been reported so far in Ae. aegypti in Africa [17][18][19][20][21].…”