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Insecticide resistance in Aedes aegypti populations from Ceara, Brazil

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Lima, Estelita Pereira, Paiva, Marcelo Henrique Santos, de Araujo, Ana Paula, da Silva, Ellyda Vansessa Gomes, da Silva, Ulisses Mariano, de Oliveira, Lucia Nogueira, Santana, Antonio Euzebio G, Barbosa, Clarisse Nogueira, Neto, Clovis C de Paiva, Goulart, Marilia OF, Wilding, Craig, Ayres, Constancia Flavia Junqueira and Melo Santos, Maria Alice V (2011) 'Insecticide resistance in Aedes aegypti populations from Ceara, Brazil'. Parasites & Vectors, Vol 4, e5.

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Abstract

BACKGROUND

Organophosphates and pyrethroids are used widely in Brazil to control Aedes aegypti, the main vector of dengue viruses, under the auspices of the National Programme for Dengue Control. Resistance to these insecticides is widespread throughout Brazil. In Ceara the vector is present in 98% of districts and resistance to temephos has been reported previously. Here we measure resistance to temephos and the pyrethroid cypermethrin in three populations from Ceara and use biochemical and molecular assays to characterise resistance mechanisms.

RESULTS

Resistance to temephos varied widely across the three studied populations, with resistance ratios (RR95) of 7.2, 30 and 192.7 in Juazeiro do Norte, Barbalha and Crato respectively. The high levels of resistance detected in Barbalha and Crato (RR95 [greater than or equal to] 30) imply a reduction of temephos efficacy, and indeed in simulated field tests reduced effectiveness was observed for the Barbalha population. Two populations (Crato and Barbalha) were also resistant to cypermethrin, whilst Juazeiro do Norte showed only an altered susceptibility. The Ile1011Met kdr mutation was detected in all three populations and Val1016Ile in Crato and Juazeiro do Norte. 1011Met was significantly associated with resistance to cypermethrin in the Crato population. Biochemical tests showed that only the activity of esterases and GST, among the tested detoxification enzymes, was altered in these populations when compared with the Rockefeller strain.

CONCLUSIONS

Our results demonstrate that two A. aegypti populations from Ceara are under strong selection pressure by temephos, compromising the field effectiveness of this organophosphate. Our results also provide evidence that the process of reducing resistance to this larvicide in the field is difficult and slow and may require more than seven years for reversal. In addition, we show resistance to cypermethrin in two of the three populations studied, and for the first time the presence of the allele 1016Ile in mosquito populations from northeastern Brazil. A significant association between 1011Met and resistance was observed in one of the populations. Target-site mechanisms seem not to be implicated in temephos resistance, reinforcing the idea that for the studied populations, detoxification enzymes most likely play a major role in the resistance to this insecticide.

Item Type: Article
Additional Information: The electronic version of this article is the complete one and can be found online at: http://www.parasitesandvectors.com/content/4/1/5
Subjects: QW Microbiology and Immunology > Immune Responses > QW 700 Infection. Mechanisms of infection and resistance.
QX Parasitology > Insects. Other Parasites > QX 510 Mosquitoes
QX Parasitology > Insects. Other Parasites > QX 525 Aedes
QX Parasitology > Insects. Other Parasites > QX 650 Insect vectors
WA Public Health > Preventive Medicine > WA 110 Prevention and control of communicable diseases. Transmission of infectious diseases
WA Public Health > Preventive Medicine > WA 240 Disinfection. Disinfestation. Pesticides (including diseases caused by)
WB Practice of Medicine > Medical Climatology > WB 710 Diseases of geographic areas
WC Communicable Diseases > Virus Diseases > Infectious Mononucleosis. Arbovirus Infections > WC 528 Dengue
Digital Object Identifer (DOI): https://doi.org/10.1186/1756-3305-4-5
Depositing User: Users 183 not found.
Date Deposited: 04 Mar 2011 13:12
Last Modified: 22 Feb 2018 16:11
URI: http://archive.lstmed.ac.uk/id/eprint/1730

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