Influence of blood meal and age of mosquitoes on susceptibility to pyrethroids in Anopheles gambiae from Western Kenya.

Publisher: BioMed Central Country of Publication: England NLM ID: 101139802 Publication Model: Electronic Cited Medium: Internet ISSN: 1475-2875 (Electronic) Linking ISSN: 14752875 NLM ISO Abbreviation: Malar J Subsets: MEDLINE

Original Publication: London : BioMed Central, [2002-

Drug Tolerance*; Anopheles/*drug effects ; Anopheles/*physiology ; Insecticides/*pharmacology ; Pyrethrins/*pharmacology; Age Factors ; Animals ; Anopheles/classification ; Anopheles/genetics ; Feeding Behavior ; Female ; Genotyping Techniques ; Kenya ; Nitriles/pharmacology ; Polymerase Chain Reaction

Background: Physiological characteristics (age and blood feeding status) of malaria vectors can influence their susceptibility to the current vector control tools that target their feeding and resting behaviour. To ensure the sustainability of the current and future vector control tools an understanding of how physiological characteristics may contribute to insecticide tolerance in the field is fundamental for shaping resistance management strategies and vector control tools. The aim of this study was to determine whether blood meal and mosquito age affect pyrethroid tolerance in field-collected Anopheles gambiae from western Kenya.
Methods: Wild mosquito larvae were reared to adulthood alongside the pyrethroid-susceptible Kisumu strain. Adult females from the two populations were monitored for deltamethrin resistance when they were young at 2-5 days old and older 14-16 days old and whether fed or unfed for each age group. Metabolic assays were also performed to determine the level of detoxification enzymes. Mosquito specimens were further identified to species level using the polymerase chain reaction (PCR) method.
Results: Anopheles gambiae sensu stricto was the predominant species comprising 96% of specimens and 2.75% Anopheles arabiensis. Bioassay results showed reduced pyrethroid induced mortality with younger mosquitoes compared to older ones (mortality rates 83% vs. 98%), independently of their feeding status. Reduced mortality was recorded with younger females of which were fed compared to their unfed counterparts of the same age with a mortality rate of 35.5% vs. 83%. Older blood-fed females showed reduced susceptibility after exposure when compared to unfed females of the same age (mortality rates 86% vs. 98%). For the Kisumu susceptible population, mortality was straight 100% regardless of age and blood feeding status. Blood feeding status and mosquito age had an effect on enzyme levels in both populations, with blood fed individuals showing higher enzyme elevations compared to their unfed counterparts (P < 0.0001). The interaction between mosquito age and blood fed status had significant effect on mosquito mortality.
Conclusion: The results showed that mosquito age and blood feeding status confers increased tolerance to insecticides as blood feeding may be playing an important role in the toxicity of deltamethrin, allowing mosquitoes to rest on insecticide-treated materials despite treatment. These may have implications for the sustained efficacy of indoor residual spraying and insecticide-treated nets based control programmes that target indoor resting female mosquitoes of various gonotrophic status.

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R01 AI050243 United States AI NIAID NIH HHS; U19 AI129326 United States AI NIAID NIH HHS; UL1 TR001414 United States TR NCATS NIH HHS; D43 TW001505 United States TW FIC NIH HHS; NACOSTI/RCD/ST&I/6TH CALL MSC/064 National Commission for Science, Technology and Innovation; RO1 A1123074 National Institute of Health; R01 AI123074 United States AI NIAID NIH HHS

Keywords: Age; Anopheles gambiae; Feeding status; Kenya; Pyrethroid resistance

0 (Insecticides)
0 (Nitriles)
0 (Pyrethrins)
2JTS8R821G (decamethrin)

Date Created: 20190404 Date Completed: 20190429 Latest Revision: 20240715

20250114

PMC6444593

10.1186/s12936-019-2746-6

30940139