Abstract
Dengue is an important mosquito borne viral disease in Martinique Island (French West Indies). The viruses responsible for dengue are transmitted by Aedes aegypti, an indoor day-biting mosquito. The most effective proven method for disease prevention has been by vector control by various chemical or biological means. Unfortunately insecticide resistance has already been observed on the Island and recently showed to significantly reduce the efficacy of vector control interventions. In this study, we investigated the distribution of resistance and the underlying mechanisms in nine Ae. aegypti populations. Statistical multifactorial approach was used to investigate the correlations between insecticide resistance levels, associated mechanisms and environmental factors characterizing the mosquito populations. Bioassays revealed high levels of resistance to temephos and deltamethrin and susceptibility to Bti in the 9 populations tested. Biochemical assays showed elevated detoxification enzyme activities of monooxygenases, carboxylesterases and glutathione S-tranferases in most of the populations. Molecular screening for common insecticide target-site mutations, revealed the presence of the “knock-down resistance” V1016I Kdr mutation at high frequency (>87%). Real time quantitative RT-PCR showed the potential involvement of several candidate detoxification genes in insecticide resistance. Principal Component Analysis (PCA) performed with variables characterizing Ae. aegypti from Martinique permitted to underline potential links existing between resistance distribution and other variables such as agriculture practices, vector control interventions and urbanization. Insecticide resistance is widespread but not homogeneously distributed across Martinique. The influence of environmental and operational factors on the evolution of the resistance and mechanisms are discussed.
Highlights
Dengue fever is a major public health problem in Martinique Island (French-West-Indies) and occurs in an endemo-epidemic pattern [1]
For Bti, a slight resistance to Bti toxins could not be excluded [33], the significant resistant ratios (RRs) measured for Martinique populations compared to the Bora-Bora test population may underline a different genetic background between field populations and laboratory test population
Among target-site mutations conferring resistance to chemical insecticides, only the V1016I Kdr mutation was found in Martinique populations, confirming the results previously obtained by Saavedra-Rodriguez et al [9] in South America and Caribbean
Summary
Dengue fever is a major public health problem in Martinique Island (French-West-Indies) and occurs in an endemo-epidemic pattern [1]. Vector control programs are facing operational challenges with the emergence and development of insecticide resistance in dengue vectors, especially Ae. aegypti [3]. In Martinique, resistance to organophosphates (OPs) and pyrethroids (PYRs) has been reported since the 1980s and 1990s respectively [4,5], and this resistance has recently been shown to be negatively impacting on the efficacy of vector control interventions [6]. A molecular study conducted by Marcombe [7] showed the involvement of both metabolic and target site based resistance mechanisms in a wild population of Martinique (Vauclin) strongly resistant to OPs and PYRs. Biochemical assays revealed significant elevated activities of cytochrome P450 monooxygenases (P450s), glutathione S-transferases (GSTs) and carboxy/cholinesterases (CCEs) at both larval and adult stages. Sequencing of the voltage-gated sodium channel showed high allelic frequency (71%) of the ‘‘knockdown resistance’’ (Kdr) mutation (V1016I) in this Martinique population which confers resistance to DDT and PYRs [8,9]
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