Analysing deltamethrin susceptibility and pyrethroid esterase activity variations in sylvatic and domestic Triatoma infestans at the embryonic stage

Pablo Luis Santo-Orihuela,Guillermo Carvajal,Maria Ines Picollo,Claudia Viviana Vassena

doi:10.1590/0074-0276130184

Pablo Luis Santo-Orihuela, Guillermo Carvajal + Show 2 more

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https://doi.org/10.1590/0074-0276130184

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Abstract

The aim of the present work was to study the deltamethrin susceptibility of eggs from Triatoma infestans populations and the contribution of pyrethroid esterases to deltamethrin degradation. Insects were collected from sylvatic areas, including Veinte de Octubre and Kirus-Mayu (Bolivia) and from domiciliary areas, including El Palmar (Bolivia) and La Pista (Argentina). Deltamethrin susceptibility was determined by dose-response bioassays. Serial dilutions of deltamethrin (0.0005-1 mg/mL) were topically applied to 12-day-old eggs. Samples from El Palmar had the highest lethal dose ratio (LDR) value (44.90) compared to the susceptible reference strain (NFS), whereas the Veinte de Octubre samples had the lowest value (0.50). Pyrethroid esterases were evaluated using 7-coumaryl permethrate (7-CP) on individually homogenised eggs from each population and from NFS. The El Palmar and La Pista samples contained 40.11 and 36.64 pmol/min/mg protein, respectively, and these values were statistically similar to NFS (34.92 pmol/min/mg protein) and different from Kirus-Mayu and Veinte de Octubre (27.49 and 22.69 pmol/min/mg protein, respectively). The toxicological data indicate that the domestic populations were resistant to deltamethrin, but no statistical contribution of 7-CP esterases was observed. The sylvatic populations had similar LDR values to NFS, but lower 7-CP esterase activities. Moreover, this is the first study of the pyrethroid esterases on T. infestans eggs employing a specific substrate (7-CP).

Highlights

The aim of the present work was to study the deltamethrin susceptibility of eggs from Triatoma infestans populations and the contribution of pyrethroid esterases to deltamethrin degradation
This study was the first analysis of pyrethroid esterase activities in eggs from sylvatic T. infestans using a specific substrate, namely, 7-coumaryl permethrate (7-CP) (Santo-Orihuela et al 2006)
Previous studies have demonstrated the importance of sylvatic T. infestans and its possible role in recolonising insecticide-treated houses (Noireau 2009, Waleckx et al 2012)

Summary

Introduction

The aim of the present work was to study the deltamethrin susceptibility of eggs from Triatoma infestans populations and the contribution of pyrethroid esterases to deltamethrin degradation. The sylvatic populations had similar LDR values to NFS, but lower 7-CP esterase activities This is the first study of the pyrethroid esterases on T. infestans eggs employing a specific substrate (7-CP). Triatoma infestans (Klug 1834) (Hemiptera, Reduviidae, Triatominae) is the main vector of Trypanosoma cruzi, which is the parasite responsible for causing Chagas disease At present, this endemic infection affects approximately nine million people in Argentina and Bolivia (Schofield et al 2006). A study by Alarico et al (2010) demonstrated deltamethrin-resistant T. infestans populations from this region were susceptible to a micro-encapsulated formulation containing organophosphate insecticides. The development of resistance in this and other regions has led investigators to evaluate the toxicity of non-pyrethroid insecticides against T. infestans (Carvajal et al 2012) Most of these studies were conducted in T. infestans populations from intradomiciliary environments. Earlier studies demonstrated differences in the expression of resistance in eggs from pyrethroid-resistant populations

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