Dynamics of insecticide resistance in the malaria vector Anopheles gambiae s.l. from an area of extensive cotton cultivation in Northern Cameroon

Abstract

Summaryobjective To explore temporal variation in insecticide susceptibility of Anopheles gambiae s.l. populations to the four chemical groups of insecticides used in public health and agriculture, in close match with the large-scale cotton spraying programme implemented in the cotton-growing area of North Cameroon.methods Mosquito larvae were collected in 2005 before (mid June), during (mid August) and at the end (early October) of the cotton spraying programme. Larvae were sampled in breeding sites located within the cotton fields in Gaschiga and Pitoa, and in Garoua, an urban cotton-free area that served as a control. Insecticide susceptibility tests were carried out with 4% DDT (organochlorine), 0.4% chlorpyrifos methyl (organophosphate), 0.1% propoxur (carbamate), 0.05% deltamethrin and 0.75% permethrin (pyrethroids).results Throughout the survey, An. gambiae s.l. populations were completely susceptible to carbamate and organophosphate, whereas a significant decrease of susceptibility to organochlorine and pyrethroids was observed during spraying in cotton-growing areas. Tolerance to these insecticides was associated with a slight increase of knockdown times compared to the reference strain. Among survivor mosquitoes, the East and West African Kdr mutations were detected only in two specimens of An. gambiae s.s. (n = 45) and not in Anopheles arabiensis (n = 150), suggesting metabolic-based resistance mechanisms.conclusions Environmental disturbance due to the use of insecticides in agriculture may provide local mosquito populations with the enzymatic arsenal selecting tolerance to insecticides.

Resting Behaviour of Deltamethrin-Resistant Malaria Vectors, Anopheles arabiensis and Anopheles coluzzii, from North Cameroon: Upshots from a Two-Level Ordinary Logit Model

“…arabiensis and An. coluzzii recorded in this study was consistent with previous studies conducted in the north Cameroon Region [11,19,40]. Furthermore, these data provided evidence of widespread deltamethrin resistance in species of the An.…”

“…gambiae were previously recorded over time and between localities in the north Cameroon. More interestingly, both species were resistant to DDT and deltamethrin, and the resistance steadily increased throughout the rainy season [11]. In other studies, An.…”

“…arabiensis in the analysed samples was consistent with the distribution of species of the An. gambiae complex in north Cameroon [11,15,19]. Since data collection for the current study was done between October and November 2011, the observed distribution of sibling species of An.…”

“…However, several studies have reported insecticide resistance in these three mosquito species, threatening the progress towards malaria elimination in the country [10][11][12]. Field observations have shown that the emergence of insecticide resistance is favoured by the abusive and anarchic use of pesticides in public health and/or in agriculture [11,13]. The regions that are mostly concerned with resistance are the North, Centre, Littoral, West and North West.…”

Susceptibility test of female anopheles mosquitoes to ten insecticides for indoor residual spraying (IRS) baseline data collection in Northeastern Nigeria

“…The farmers in the community also use cypermethrin, lambdacyhalothrin, deltamethrin, dichlovos and primiphos-methyl for agricultural crop protection. Previous researchers have reported that exposure of malarial vectors to crop protection insecticides could result in development of insecticide resistance (Etang et al, 2003;Awolola et al, 2007;Müller et al, 2008;Chouaibou et al, 2008;Bigoga et al, 2012;Philbert et al, 2014). LLIN was used in Misau for protection against mosquitoes since 2002 to date and it may induce selections to pyrethroids insecticides.…”