Synergy in efficacy of fungal entomopathogens and permethrin against West African insecticide-resistant Anopheles gambiae mosquitoes

M. Farenhorst, B.G.J. Knols, M.B. Thomas, A.F.V. Howard, W. Takken, M. Rowland, R. N'Guessan

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Abstract

Background Increasing incidences of insecticide resistance in malaria vectors are threatening the sustainable use of contemporary chemical vector control measures. Fungal entomopathogens provide a possible additional tool for the control of insecticide-resistant malaria mosquitoes. This study investigated the compatibility of the pyrethroid insecticide permethrin and two mosquito-pathogenic fungi, Beauveria bassiana and Metarhizium anisopliae, against a laboratory colony and field population of West African insecticide-resistant Anopheles gambiae s.s. mosquitoes. Methodology/Findings A range of fungus-insecticide combinations was used to test effects of timing and sequence of exposure. Both the laboratory-reared and field-collected mosquitoes were highly resistant to permethrin but susceptible to B. bassiana and M. anisopliae infection, inducing 100% mortality within nine days. Combinations of insecticide and fungus showed synergistic effects on mosquito survival. Fungal infection increased permethrin-induced mortality rates in wild An. gambiae s.s. mosquitoes and reciprocally, exposure to permethrin increased subsequent fungal-induced mortality rates in both colonies. Simultaneous co-exposure induced the highest mortality; up to 70.3±2% for a combined Beauveria and permethrin exposure within a time range of one gonotrophic cycle (4 days). Conclusions/Significance Combining fungi and permethrin induced a higher impact on mosquito survival than the use of these control agents alone. The observed synergism in efficacy shows the potential for integrated fungus-insecticide control measures to dramatically reduce malaria transmission and enable control at more moderate levels of coverage even in areas where insecticide resistance has rendered pyrethroids essentially ineffective.
Original languageEnglish
Article numbere12081
Number of pages10
JournalPLoS ONE
Volume5
Issue number8
DOIs
Publication statusPublished - 2010

Keywords

  • metarhizium-anisopliae
  • culex-quinquefasciatus
  • malaria mosquitos
  • pyrethroid resistance
  • infection
  • vectors
  • deuteromycotina
  • biopesticides
  • coleoptera
  • knockdown

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    Farenhorst, M., Knols, B. G. J., Thomas, M. B., Howard, A. F. V., Takken, W., Rowland, M., & N'Guessan, R. (2010). Synergy in efficacy of fungal entomopathogens and permethrin against West African insecticide-resistant Anopheles gambiae mosquitoes. PLoS ONE, 5(8), [e12081]. https://doi.org/10.1371/journal.pone.0012081