Pyrethroid and Carbamate Resistance in Anopheles funestus Giles along Lake Kariba in Southern Zambia

Abstract

Whereas data on insecticide resistance and its underlying mechanisms exist for parts of Zambia, data remain limited in the southern part of the country. This study investigated the status of insecticide resistance, metabolic mechanisms, and parasite infection in Anopheles funestus along Lake Kariba in southern Zambia. Indoor-resting mosquitoes were collected from 20 randomly selected houses within clusters where a mass drug administration trial was conducted and raised to F1 progeny. Non-blood-fed 2-to 5-day-old female An. funestus were exposed to WHO insecticide-impregnated papers with 0.05% deltamethrin, 0.1% bendiocarb, 0.25% pirimiphos-methyl, or 4% dichlorodiphenyl-trichloroethane (DDT). In separate assays, An. funestus were pre-exposed to piperonyl butoxide (PBO) to determine the presence of monooxygenases. Wild-caught An. funestus that had laid eggs for susceptibility assays were screened for circumsporozoite protein of Plasmodium falciparum by ELISA, and sibling species were identified by polymerase chain reaction. Anopheles funestus showed resistance to deltamethrin and bendiocarb but remained susceptible to pirimiphos-methyl and DDT. The pre-exposure of An. funestus to PBO restored full susceptibility to deltamethrin but not to bendiocarb. The overall sporozoite infection rate in An. funestus populations was 5.8%. Detection of pyrethroid and carbamate resistance in An. funestus calls for increased insecticide resistance monitoring to guide planning and selection of effective insecticide resistance management strategies. To prevent the development of resistance and reduce the underlying vectorial capacity of mosquitoes in areas targeted for malaria elimination, an effective integrated vector management strategy is needed.

Six decades of malaria vector control in southern Africa: a review of the entomological evidence-base

“…These insecticides have been used for IRS and in LLINs. Despite a high reliance on insecticides for the control of malaria vectors for decades, insecticide resistance is not well documented, with few reports from Mozambique [ 55 , 56 , 60 , 62 , 64 , 65 , 74 , 83 , 90 , 208 ], Zimbabwe [ 121 , 165 , 169 , 170 ] and Zambia [ 110 , 111 , 121 , 122 , 143 ], one from Botswana [ 40 ]. Information from Eswatini and Namibia is lacking altogether.…”

“…An. funestus has been reported to be resistant to pyrethroids [ 60 , 62 , 64 , 111 , 121 , 143 , 208 ], and the carbamate bendiocarb [ 170 ]. Low-level resistance to the carbamate propoxur in An.…”

Malaria risk and receptivity: Continuing development of insecticide resistance in the major malaria vector Anopheles arabiensis in northern KwaZulu-Natal, South Africa

“…funestus in southern Africa. [27][28][29][30] Volume 118| An assessment of resistance mechanisms can yield important information on where cross-resistances between insecticide classes are likely, and on how quickly resistance might develop to high levels in an affected vector population under selection pressure. The synergist data given here suggests that cytochrome P450s (oxygenases) and general esterases are at least partially responsible for the pyrethroidand carbamate-resistant phenotypes, although these data need to be interpreted with caution.…”

Moving from Malaria Burden Reduction toward Elimination: An Evaluation of Mass Drug Administration in Southern Province, Zambia

“…31 We also report the findings of several studies conducted concurrently that investigated various aspects of the trial. These include studies on the acceptability of treatment, 32 MDA coverage, 33 DHAP efficacy and adherence to the treatment regimen, 34 RDT performance, 35 infection incidence, 36 parasite genotypes before and after the intervention, 37 human movement and the relationship between travel history and malaria infection status, 38 insecticide resistance and parasite infection in Anopheles funestus mosquitoes in the study area, 39 and the cost-effectiveness of adding an MDA or fMDA strategy to the standard-of-care malaria control in Southern Province. 40 Although specific to the trial and study area, many of the issues explored in these articles are germane to consideration of the potential usefulness of population-based drug strategies in other settings.…”