Susceptibility status of <i>Anopheles gambiae</i> s.l. (Diptera: Culicidae) from cabbage growing areas associated with pyrethroid and organophosphate use in Accra, Ghana

Abstract

Resistance in malaria vectors is likely to be caused by the massive use of insecticides in agriculture. Anopheles gambiae s.l. collected from breeding grounds in two cabbage growing areas within Accra were assessed for levels of resistance to 0.75% permethrin, 0.05% deltamethrin, 5% malathion and 4% DDT using standard WHO susceptibility test kits. Pyrethroid and organophosphate residue levels in soil and runoff water from these cabbage farms were determined and possible association between resistance and residue levels were established. Compared to the susceptible 'Kisumu' strain, both Korle-Bu and Airport populations were highly resistant to DDT and gave resistance levels which were over nine-fold for permethrin and over 2.5-fold for deltamethrin. Both wild and susceptible populations showed full susceptibility to malathion. The S and M forms of A. gambiae s.s. were found to occur in sympatry in the two study sites with a higher frequency of S form in the Airport area. Toxicity testing of extracts of soil and runoff water from these cabbage farms, using brine shrimp lethality tests, showed high level of toxicity, indicative of the presence of residues of insecticides. Differential fractionation of these extracts using solid phase extractor (SPE) suggests that the bulk of residues in these extracts may be pyrethroids and organophosphates. No correlation was observed between either residue levels or residual bioactivity in soil and runoff water, and resistance levels in A. gambiae s.l. populations, collected from breeding grounds within the farms under investigation. It is proposed that resistance in A. gambiae larvae in these breeding sites contaminated with agricultural insecticides may have occurred over time due to continuous exposure to sub-lethal doses.

Characterization of Anopheles gambiae s.l. and insecticide resistance profile relative to physicochemical properties of breeding habitats within Accra Metropolis, Ghana

“…gambiae complex found in the study area. This finding is consistent with earlier studies in the grater Accra Region (Appawu, 2001;Midega, 2001;Adeniran, 2002;Sibomana, 2002;Otieno, 2004;Achonduh, 2005). The two molecular forms of An.…”

“…gambiae s.l. to insecticides have been conducted in Ghana (Adasi, et al, 2000;Adeniran, 2002;Otieno, 2004;Yawson et al, 2004;Achonduh, 2005;Kahindi, 2005), it is still important to continue monitoring changing trends of resistance. The information provides a basis for ascertaining continued susceptibility to and efficacy of pyrethroids, and for vector insecticide resistance management.…”

Bio-efficacy, user perception and acceptability of pyrethroid based mosquito coils in controlling <i>Anopheles gambiae</i> s.l., in some parts of Accra, Ghana

“…which reported a higher knockdown and mortality rate of mosquito susceptibility test upon combinations of different concentration and different active ingredients of herbal mosquito coils. The study also agrees with other studies in the Greater Accra region which reported resistance to pyrethroid based vector control methods (Adeniran, 2002;Achonduh et al, 2008;Boakye et al, 2009). The reasons why An.…”

“…gambiae s.s. population in the area is consistent with studies by Achonduh et al (2008), Adeniran (2002) in the Accra metropolis and Diabate et al (2002) in Burkina Faso, where the kdr gene was found to be highly present in An. gambiae s.s. in their respective areas.…”

“…gambiae s.s. from the study area gave very low mortalities after exposure to the three coils could be due to the fact that, this same group of insecticides is continuously used by the inhabitants in the form of aerosols or coils to control mosquitoes. Studies by Achonduh et al (2008), Adeniran, (2002 and Boakye et al (2009) reported that the use of pyrethroids based pesticides in farms might be contributing in conferring kdr in Anopheles spp. in the study area.…”