Composition of Mosquito Fauna and Insecticide Resistance Status of Anopheles gambiae complex in Itang special woreda, Gambella, Southwestern Ethiopia

Abstract IntroductionMalaria is a leading cause of morbidity and mortality mainly in sub-Saharan African countries. Plasmodium falciparum and P. vivax are the dominant malaria parasites responsible for the majority of malaria cases in Africa. The aim of this study was to investigate composition of mosquito fauna and insecticide resistance status of Anopheles mosquito in Itang special woreda (district), Gambella, southwestern Ethiopia.Materials and methodsAdult mosquitoes were sampled from September 2020 to Feburary 2021 using Centers for Disease Control and Prevention (CDC) light trap and Pyrethrum Spray Catch (PSC). Moreover, mosquito larvae were collected from different breeding sites and reared to adults. Susceptibility tests were conducted on adult two to three days old non blood fed female Anopheles gambiae s.l following world health organization (WHO) standard susceptibility test procedure. Insecticide impregnated papers with deltamethrin (0.05%), alpha-cypermethrin (0.05%), propoxur (0.1%), pirimiphos-methyl (0.25%) and bendiocarb (0.1%) were used to assess susceptibility status of Anopheles gambiae s.l populations in the study area. Moreover, molecular diagnostics were done for the identification of member species of Anopheles gambiae s.l and detection of knockdown resistance ( kdr ) using species specific polymerase chain reaction (PCR) and allele specific PCR.ResultsIn total, 468 adult mosquitoes were collected from different houses. Culex mosquitoes were the most dominant ( 80.4% ) followed by Anopheles mosquitoes. Three species of Anopheles mosquitoes ( An. coustani, An. pharoensis , and An. gambiae (s.l.)) were identified, of which An. coustani was the dominant ( 8.1%) species. Out of 468 adult mosquitoes, 294 were blood fed while 46 were half-gravid and gravid. The WHO bioassay tests revealed that the populations of An. gambiae s.l in the study area are resistant against alpha-cypermethrin and deltamethrin whereas, susceptible to bendiocarb, pirimiphos-methyl and propoxur. Out of the total 86 An. gambiae s.l specimens assayed, 79 (92%) successfully amplified and all were identified as An. arabiensis . West African Kdr (L1014F) mutation was detected with high Kdr allele frequency ranging from 67–88%.ConclusionThe detection of target site mutation, kdr L1014F allele, coupled with the phenotypic resistance against alpha-cypermethrin and deltamethrin call for continuous resistance monitoring.