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Memórias do Instituto Oswaldo Cruz
Fundação Oswaldo Cruz, Fiocruz
ISSN: 1678-8060
EISSN: 1678-8060
Vol. 94, No. 1, 1999, pp. 115-120
Bioline Code: oc99022
Full paper language: English
Document type: Research Article
Document available free of charge

Memórias do Instituto Oswaldo Cruz, Vol. 94, No. 1, 1999, pp. 115-120

 en Evaluation of Insecticide Resistance and Biochemical Mechanisms in a Population of Culex quinquefasciatus (Diptera: Culicidae) from São Paulo, Brazil
José Eduardo Bracco; José Maria S Barata & Osvaldo Marinotti

Abstract

To establish an insecticidal resistance surveillance program, Culex
quinquefasciatus mosquitoes from São Paulo, Brazil, were colonized (PIN95 strain)
and analyzed for levels of resistance. The PIN95 strain showed low levels of resistance to
organophosphates [malathion (3.3-fold), fenitrothion (11.2-fold)] and a carbamate [propoxur
(3.0-fold)]. We also observed an increase of 7.4 and 9.9 in a and b esterase activities,
respectively, when compared with the reference IAL strain. An alteration in the sensitivity of
acetylcholinesterase to insecticide inhibition was also found in the PIN95 mosquitoes. The
resistant allele (Ace.1R), however, was found at low frequencies (0.12) and
does not play an important role in the described insecticide resistance.

One year later, Cx. quinquefasciatus mosquitoes were collected (PIN96 strain) at the same site and compared to the PIN95 strain. The esterase activity patterns observed for the PIN96 strain were similar to those of the PIN95 mosquitoes. However the occurrence of the Ace.1R allele was statistically higher in the PIN96 strain.

The results show that esterase-based insecticide resistance was established in the PIN95 Cx. quinquefasciatus population and that an acethylcholinesterase based resistant mechanism has been selected for. A continuous monitoring of this phenomenon is fundamental for rational mosquito control and insecticide application programs.

Keywords
Culex quinquefasciatus - insecticide resistance - acethylcholinesterase - esterase - control

 
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