Trends in DDT and pyrethroid resistance in Anopheles gambiaes.s. populations from urban and agro-industrial settings in southern Cameroon

Abstract

BackgroundPyrethroid insecticides are widely used for insect pest control in Cameroon. In certain insect species, particularly the malaria vector Anopheles gambiae, resistance to this class of insecticides is a source of great concern and needs to be monitored in order to sustain the efficacy of vector control operations in the fields. This study highlights trends in DDT and pyrethroid resistance in wild An. gambiae populations from South Cameroon.MethodsMosquitoes were collected between 2001 and 2007 in four sites in South Cameroon, where insecticides are used for agricultural or personal protection purposes. Insecticide use was documented in each site by interviewing residents. Batches of 2-4 days old adult female mosquitoes reared from larval collections were tested for susceptibility to DDT, permethrin and deltamethrin using standard WHO procedures. Control, dead and survivors mosquitoes from bioassays were identified by PCR-RFLP and characterized for the kdr mutations using either the AS-PCR or the HOLA method.ResultsFour chemical insecticide groups were cited in the study sites: organochlorines, organophosphates, carbamates and pyrethroids. These chemicals were used for personal, crop or wood protection. In the four An. gambiae populations tested, significant variation in resistance levels, molecular forms composition and kdr frequencies were recorded in the time span of the study. Increases in DDT and pyrethroid resistance, as observed in most areas, were generally associated with an increase in the relative frequency of the S molecular form carrying the kdr mutations at higher frequencies. In Mangoum, however, where only the S form was present, a significant increase in the frequency of kdr alleles between 2003 to 2007 diverged with a decrease of the level of resistance to DDT and pyrethroids. Analyses of the kdr frequencies in dead and surviving mosquitoes showed partial correlation between the kdr genotypes and resistance phenotypes, suggesting that the kdr mechanism may act with certain co-factors to be identified.ConclusionThese results demonstrate the ongoing spread of kdr alleles in An. gambiae in Central Africa. The rapid evolution of insecticide resistance in this highly dynamic and genetically polymorphic species remains a challenge for its control.

Susceptibility to DDT and pyrethroids, and detection of knockdown resistance mutation in <i>Anopheles gambiae sensu lato</i> in Southern Togo

“…It has also been detected recently in Togo (Ketoh et al, 2009). The kdr mutation has also been reported in other sub-Saharan African countries such as Equatorial Guinea and Cameroon (Reimer et al, 2005, Etang et al, 2006, Nwane et al, 2009. Though the resistance is observed in this study, deltamethrin was the most effective and had the least resistance ratio at comparable toxicity.…”

Insecticide Resistance Allele Frequencies in Anopheles gambiae before and after Anti-Vector Interventions in Continental Equatorial Guinea

“…In four villages in southern Cameroon, L1014F and L1014S were present in S form populations in 2007, and L1014F had a considerably higher frequency than L1014S. 30 These villages were sampled across a diverse landscape of urban and agroindustrial settings in which pyrethroids and other insecticides are commonly used for agricultural, household nuisance reduction and public health uses, and L1014F increased substantially In Gabon, which borders Equatorial Guinea to the south, Pinto and others observed a much higher frequency of L1014S (63.0%) than L1014F (37.0%) in an S form population only approximately 100 km from the southern border of Equatorial Guinea. 8 Therefore, Gabon provides another possible entry route for L1014F and/or L1014S.…”

“…28 One such target is the acetylcholinesterase-1 (ace-1 R ), which serves an essential role in neurotransmission in many arthropods and is targeted by several classes of insecticides, including carbamates and organophosphates. 29,30 Target site resistance in this gene, the ace-1 R allele in An. gambiae, is conferred through a single amino acid substitution from glycine to serine at residue 119.…”

Determination of toxic effects of commercial and local mosquito repellents in <i>Oryctolagus cuniculus</i> (New Zealand white)

“…Azizi and Henry (1991) reported that long term exposure to mosquito coil smoke has been shown by some workers to cause asthma and persistent sneezing in children. Appearance of resistant parasites and mosquito strains have paved way to search for new products (Nwane et al, 2009) Orange peels (Citrus sinensis) are mostly thrown into the garbage after which they eventually find their way into piles of wasted products. Interestingly the chemical contents of the peels have pharmacological activities (Muhtadi et al, 2015).…”