Pyrethroid resistance in the major malaria vector Anopheles arabiensis in Nouakchott, Mauritania

Abstract

BackgroundMauritania is one of the African countries with ongoing malaria transmission where data on insecticide resistance of local malaria vectors are limited despite an increasing use of long-lasting insecticide-treated nets (LLINs) as the main intervention for vector control. This study presents an evaluation of the level of insecticide resistance of Anopheles arabiensis in Nouakchott.MethodsAnopheles gambiae (s.l.) larvae were collected in breeding sites during the rainy season (August-September) in 2015 and 2016 from two selected sites in Nouakchott and reared until emergence. Adult anopheline mosquitoes were tested against malathion (5%), bendiocarb (0.1%), permethrin (0.75%) and deltamethrin (0.05%) using standard World Health Organization (WHO) insecticide-impregnated papers. PCR assays were used for the identification of An. gambiae (s.l.) sibling species as well as knockdown resistance (kdr).ResultsThe mean knockdown times 50% (KDT50) and 95% (KDT95) were 66 ± 17 and 244 ± 13 min, respectively, for permethrin in 2015. The KDT50 and the KDT95 were 39 ± 13 and 119 ± 13 min, respectively, for deltamethrin. The KDT50 and the KDT95 doubled for both molecules in 2016. The mortality rates 24 h post-exposure revealed that An. arabiensis populations in Nouakchott were fully susceptible to bendiocarb and malathion in 2015 as well as in 2016, while they were resistant to permethrin (51.9% mortality in 2015 and 24.1% mortality in 2016) and to deltamethrin (83.7% mortality in 2015 and 39.1% mortality in 2016). The molecular identification showed that Anopheles arabiensis was the only malaria vector species collected in Nouakchott in 2015 and 2016. Both the West and East African kdr mutant alleles were found in An. arabiensis mosquitoes surviving exposure to pyrethroid insecticide, with a high rate of homozygous resistant genotypes (54.3% for the West African kdr mutation and 21.4% for the East African kdr mutation) and a significant departure from Hardy-Weinberg proportions (χ2 = 134, df = 3, P < 0.001).ConclusionsThe study showed high levels of pyrethroid resistance in An. arabiensis populations in Nouakchott and presence of both West and East African kdr alleles in the resistant phenotype. These results highlight a need for routine monitoring of susceptibility of malaria vector populations to insecticides used in public health programs.

Status of insecticide resistance and its biochemical and molecular mechanisms in Anopheles stephensi (Diptera: Culicidae) from Afghanistan

“…gambiae in many West African countries, the frequency of kdr west has reached fixation (total homozygocity) [54, 74–77]. In other parts of Africa, co-occurrence of kdr west and kdr east with relatively high frequency is reported [34, 37, 71, 73, 78]. It has been argued that even with high kdr mutation rates, LNs may still be effective in protecting people against malaria [79–85].…”

Treatment-seeking and uptake of malaria prevention strategies among pregnant women and caregivers of children under-five years during COVID-19 pandemic in rural communities in South West Uganda: a qualitative study

“…Despite the proven efficacy of prevention programs, the burden of malaria remains unacceptably high due to challenges related to new pyrethroid-resistant mosquito strains, and laxity in uptake of prevention measures [9,[14][15][16][17][18][19]. A 2016 field survey in a rural district in Uganda [17], showed high malaria cases in the communities, despite the household possession of ITNs.…”

Malaria epidemiology in Kobeni department, southeastern Mauritania from 2015 to 2017

“…is the main malaria vector in the country [5][6][7]. Pyrethroid resistance in Anopheles arabiensis has recently been reported in the Saharan and sahelian zones [8,9].…”