Insecticide resistance status in Anopheles gambiae (s.l.) in coastal Kenya

Authors: MUNYWOKI, DANIEL - Kenyatta University; KOKWARO, ELIZABETH - Kenyatta University; MWANGANGI, JOSEPH - Kenya Medical Research Institute; Muturi, Ephantus; MBOGO, CHARLES - Kenya Medical Research Institute

Submitted to: Parasites & Vectors
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/31/2021
Publication Date: 4/20/2021
Citation: Munywoki, D.N., Kokwaro, E.D., Mwangangi, J.M., Muturi, E.J., Mbogo, C.M. 2021. Insecticide resistance status in Anopheles gambiae (s.l.) in coastal Kenya. Parasites & Vectors. 14. Article 207. https://doi.org/10.1186/s13071-021-04706-5.
DOI: https://doi.org/10.1186/s13071-021-04706-5

Interpretive Summary: Mosquito control using synthetic insecticides has played a major role in the fight against malaria. However, the growing problem of insecticide resistance against malaria vectors has become one of the major challenges facing national malaria control programs in Africa. Defining the prevalence of insecticide resistance and the underlying mechanisms of resistance in malaria mosquitoes is therefore one of the focal points for malaria research. This study investigated the insecticide resistance status of malaria vectors in Coastal Kenya against five insecticides belonging to four classes of insecticides that are commonly used in mosquito control. Malaria mosquitoes were also investigated for the presence of knockdown resistance gene mutation which is known to confer resistance to one of the insecticide classes. Malaria mosquitoes were resistant to two of the four insecticide classes. A low frequency of knockdown resistance gene mutation was detected in one of malaria mosquito species. This study demonstrates that malaria mosquitoes in Coastal Kenya are resistant to some insecticide classes used for their control and suggest that knockdown resistance mutation may be one of the mechanisms underlying resistance of malaria mosquitoes to one of the insecticide classes. This knowledge may inform development of novel strategies for resistance management.

Technical Abstract: The rapid and widespread evolution of insecticide resistance has emerged as one of the major challenges facing malaria control programs in sub-Saharan Africa. Understanding the insecticide resistance status of mosquito populations and the underlying mechanisms of insecticide resistance can inform development of effective and site-specific strategies for resistance prevention and management. This study investigated the insecticide resistance status of Anopheles gambiae sensu lato (s.l.) mosquitoes from Coastal Kenya. Anopheles gambiae s.l. larvae sampled from eight study sites were reared to adulthood in the insectary and 3-5 day old non-blood fed females were tested for susceptibility to permethrin, deltamethrin, DDT, fenitrothion and bendiocarb using the standard World Health Organization (WHO) protocol. PCR amplification of rDNA intergenic spacers was used for identification of sibling species of the Anopheles gambiae complex. The Anopheles gambiae s.l. mosquitoes were further genotyped for L1014S and L1014F knockdown resistance (kdr) mutations by real time PCR. Anopheles arabiensis was the dominant species accounting for 95.2% of the total collection followed by Anopheles gambiae s.s. at 4.8%. Anopheles gambiae s.l. mosquitoes were resistant to deltamethrin, permethrin and fenitrothion, but not bendiocarb and DDT. A low allelic frequency of 3.33% for L1014S point mutation was only detected in An. gambiae s.s. with no 1014F mutation detected in both An. gambiae s.s. and An. arabiensis. The findings of this study demonstrate phenotypic resistance in pyrethroids and organophosphates and a low level of kdr mutation which may partly be responsible for resistance to pyrethroids. This knowledge may inform development of insecticide resistance management strategies along the Kenyan Coast.