Anopheles arabiensis and An. quadriannulatus resistance to DDT in South Africa

Abstract

The malaria control programme of KwaZulu-Natal Province, South Africa, includes Mamfene and Mlambo communities. Western-type houses there are currently sprayed with deltamethrin, whereas traditional houses are sprayed with DDT for malaria control. In 2002, mosquitoes of the Anopheles gambiae complex (Diptera: Culicidae) were collected from DDT-sprayed houses, by window exit traps, and from man-baited nets outdoors. Larval collections were also carried out at Mzinweni Pan near Mlambo. Species of the An. gambiae complex were identified by rDNA polymerase chain reaction assay. The majority of samples collected by window trap and baited nets were identified as the malaria vector An. arabiensis Patton, with a few An. merus Dönitz and An. quadriannulatus (Theobald). The larval collections were predominantly An. quadriannulatus with a small number of An. arabiensis. Standard WHO insecticide susceptibility tests using 4% DDT and 0.05% deltamethrin were performed on both wild-caught females and laboratory-reared progeny from wild-caught females. Wild-caught An. arabiensis samples from window traps gave 63% and 100% mortality 24-h post-exposure to DDT or deltamethrin, respectively. Wild-caught An. arabiensis samples from man-baited net traps gave 81% mortality 24-h post-exposure to DDT. The F1 progeny from 22 An. arabiensis females showed average mortality of 86.5% 24-h post-exposure to DDT. Less than 80% mortality was recorded from five of these families. Biochemical analyses of samples from each of the families revealed comparatively high levels of glutathione-S-transferases and non-specific esterases in some families, but without significant correlation to bioassay results. Wild-caught An. quadriannulatus larvae were reared through to adults and assayed on 4% DDT, giving 47% (n = 36) mortality 24-h post-exposure. Finding DDT resistance in the vector An. arabiensis, close to the area where we previously reported pyrethroid-resistance in the vector An. funestus Giles, indicates an urgent need to develop a strategy of insecticide resistance management for the malaria control programmes of southern Africa.

Insecticide resistance in the malaria vector Anopheles arabiensis in Mamfene, KwaZulu-Natal

“…arabiensis at Mamfene were conducted in 1996 and no resistance phenotypes were recorded. 15 However, subsequent samples collected in 2002 indicated the emergence of resistance to DDT 16 which was again recorded in 2005 together with the first indication of pyrethroid resistance 7 . The 2015 data presented here affirm the presence of pyrethroid and DDT resistance in this population, albeit at a low frequency, and also indicate the comparatively recent emergence of resistance to the carbamate insecticide bendiocarb.…”

Electrostatic coating enhances bioavailability of insecticides and breaks pyrethroid resistance in mosquitoes

“…Insecticide exposures were conducted on multiple strains of pyrethroid-resistant mosquitoes, including the major malaria vectors Anopheles arabiensis (27)(28)(29), Anopheles funestus (30,31), and Anopheles gambiae s.s. (32, 33) with well-defined mechanisms and levels of resistance, using standard WHO resistance assays with 0.05% deltamethrin papers (Fig. S1).…”

High levels of DDT in breast milk: Intake, risk, lactation duration, and involvement of gender

“…Despite numerous scientific assessments recommending that safe and sustainable alternatives to DDT should be urgently investigated and deployed (De Jager et al, 2006;De Jager et al, 2009;Eskenazi et al, 2009;Bornman et al, 2010;Bouwman et al, 2011), a relatively affluent African country is in a position to do much more to reduce exposures or to move away from DDT. It must be acknowledged however, that a previous attempt to switch from DDT to pyrethroids failed (Hargreaves et al, 2003;Maharaj et al, 2005), and that the expectations of proof of safety and sustainability of alternatives have probably increased due to that failure. Added to the concerns of health effects of DDT also comes the concerns associated with pyrethroids (Bouwman et al, 2006;Bouwman and Kylin, 2009).…”