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Pestic Biochem Physiol. 2015 Jun;121:116-21. doi: 10.1016/j.pestbp.2015.03.001. Epub 2015 Mar 9.

Carbamate and pyrethroid resistance in the akron strain of Anopheles gambiae.

Author information

1
Department of Entomology, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA.
2
Department of Chemistry, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA.
3
Emerging Pathogens Institute, Department of Entomology and Nematology, University of Florida, Gainesville, FL 32610, USA.
4
Emerging Pathogens Institute, Department of Entomology and Nematology, University of Florida, Gainesville, FL 32610, USA. Electronic address: jbquist@epi.ufl.edu.

Abstract

Insecticide resistance in the malaria vector, Anopheles gambiae, is a serious problem, epitomized by the multi-resistant Akron strain, originally isolated in the country of Benin. Here we report resistance in this strain to pyrethroids and DDT (13-fold to 35-fold compared to the susceptible G3 strain), but surprisingly little resistance to etofenprox, a compound sometimes described as a "pseudo-pyrethroid." There was also strong resistance to topically-applied commercial carbamates (45-fold to 81-fold), except for the oximes aldicarb and methomyl. Biochemical assays showed enhanced cytochrome P450 monooxygenase and carboxylesterase activity, but not that of glutathione-S-transferase. A series of substituted α,α,α,-trifluoroacetophenone oxime methylcarbamates were evaluated for enzyme inhibition potency and toxicity against G3 and Akron mosquitoes. The compound bearing an unsubstituted phenyl ring showed the greatest toxicity to mosquitoes of both strains. Low cross resistance in Akron was retained by all analogs in the series. Kinetic analysis of acetylcholinesterase activity and its inhibition by insecticides in the G3 strain showed inactivation rate constants greater than that of propoxur, and against Akron enzyme inactivation rate constants similar to that of aldicarb. However, inactivation rate constants against recombinant human AChE were essentially identical to that of the G3 strain. Thus, the acetophenone oxime carbamates described here, though potent insecticides that control resistant Akron mosquitoes, require further structural modification to attain acceptable selectivity and human safety.

KEYWORDS:

Acetylcholinesterase; Anticholinesterase; Knockdown resistance; Metabolic resistance; Mosquito

PMID:
26047119
PMCID:
PMC4457939
DOI:
10.1016/j.pestbp.2015.03.001
[Indexed for MEDLINE]
Free PMC Article

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