Exploring the molecular basis of insecticide resistance in the dengue vector Aedes aegypti: a case study in Martinique Island (French West Indies)

<p>Abstract</p> <p>Background</p> <p>The yellow fever mosquito <it>Aedes aegypti </it>is a major vector of dengue and hemorrhagic fevers, causing up to 100 million dengue infections every year. As there is still no medicine and efficient vaccine available, vector control largely based on insecticide treatments remains the only method to reduce dengue virus transmission. Unfortunately, vector control programs are facing operational challenges with mosquitoes becoming resistant to commonly used insecticides. Resistance of <it>Ae. aegypti </it>to chemical insecticides has been reported worldwide and the underlying molecular mechanisms, including the identification of enzymes involved in insecticide detoxification are not completely understood.</p> <p>Results</p> <p>The present paper investigates the molecular basis of insecticide resistance in a population of <it>Ae. aegypti </it>collected in Martinique (French West Indies). Bioassays with insecticides on adults and larvae revealed high levels of resistance to organophosphate and pyrethroid insecticides. Molecular screening for common insecticide target-site mutations showed a high frequency (71%) of the sodium channel 'knock down resistance' (<it>kdr</it>) mutation. Exposing mosquitoes to detoxification enzymes inhibitors prior to bioassays induced a significant increased susceptibility of mosquitoes to insecticides, revealing the presence of metabolic-based resistance mechanisms. This trend was biochemically confirmed by significant elevated activities of cytochrome P450 monooxygenases, glutathione S-transferases and carboxylesterases at both larval and adult stages. Utilization of the microarray <it>Aedes Detox Chip </it>containing probes for all members of detoxification and other insecticide resistance-related enzymes revealed the significant constitutive over-transcription of multiple detoxification genes at both larval and adult stages. The over-transcription of detoxification genes in the resistant strain was confirmed by using real-time quantitative RT-PCR.</p> <p>Conclusion</p> <p>These results suggest that the high level of insecticide resistance found in <it>Ae. aegypti </it>mosquitoes from Martinique island is the consequence of both target-site and metabolic based resistance mechanisms. Insecticide resistance levels and associated mechanisms are discussed in relation with the environmental context of Martinique Island. These finding have important implications for dengue vector control in Martinique and emphasizes the need to develop new tools and strategies for maintaining an effective control of <it>Aedes </it>mosquito populations worldwide.</p

First report of knockdown mutations in the malaria vector Anopheles gambiae from Cameroon.

International audienceWe report the first finding of the knockdown Leu-Phe and Leu-Ser mutations associated with resistance to pyrethroids and DDT insecticides in the malaria mosquito Anopheles gambiae from Cameroon. The Leu-Phe mutation was found in both the M and S molecular forms of An. gambiae. Importantly, two specimens of the S molecular form were found to carry both mutations in a heterozygous state

Use of an Anopheles Salivary Biomarker to Assess Malaria Transmission Risk Along the Thailand-Myanmar Border.

BackgroundThe modalities of malaria transmission along the Thailand-Myanmar border are poorly understood. Here we address the relevance of using a specific Anopheles salivary biomarker to measure the risk among humans of exposure to Anopheles bites.MethodsSerologic surveys were conducted from May 2013 to December 2014 in 4 sentinel villages. More than 9400 blood specimens were collected in filter papers from all inhabitants at baseline and then every 3 months thereafter, for up to 18 months, for analysis by enzyme-linked immunosorbent assay. The relationship between the intensity of the human antibody response and entomological indicators of transmission (human biting rates and entomological inoculation rates [EIRs]) was studied using a multivariate 3-level mixed model analysis. Heat maps for human immunoglobulin G (IgG) responses for each village and survey time point were created using QGIS 2.4.ResultsThe levels of IgG response among participants varied significantly according to village, season, and age (P&lt;.001) and were positively associated with the abundance of total Anopheles species and primary malaria vectors and the EIR (P&lt;.001). Spatial clusters of high-IgG responders were identified across space and time within study villages.ConclusionsThe gSG6-P1 biomarker has great potential to address the risk of transmission along the Thailand-Myanmar border and represents a promising tool to guide malaria interventions

Seasonal abundance, blood meal sources and insecticide susceptibility in major anopheline malaria vectors from southern Mauritania

Abstract Background Malaria is endemic in the southernmost Sahelian zone of Mauritania where the major known mosquito vector is Anopheles arabiensis. Understanding seasonal population dynamics, feeding preferences and insecticide resistance status of these vectors in the area is essential to improve vector control measures implemented at a local scale. Here, malaria vector populations’ bionomics is described in two sentinel sites located in the Sahelian zone of Mauritania. Methods Between September 2014 and December 2016, longitudinal entomological surveys were conducted in Kobeni (15°49'N, 09°24'W) and Rosso (16°30'N; 15°48'W), two localities in the southern Sahelian zone of Mauritania. Adult mosquitoes were collected using indoor pyrethrum spray catch (PSC). Morphological and PCR-based methods were used to identify the species, detect Plasmodium parasites and analyze blood meals in individual mosquitoes. WHO insecticide susceptibility tests were performed with malathion (5%), bendiocarb (0.1%), permethrin (0.75%) and deltamethrin (0.05%) using female An. gambiae (s.l.) reared from larval and pupal collections from natural breeding sites. Results A total of 2702 Anopheles mosquitoes were collected by PSC during the study period comprising 2291 Anopheles gambiae (s.l.), 376 Anopheles rufipes and 35 Anopheles pharoensis. In Rosso, all mosquitoes from the An. gambiae (s.l.) complex were molecularly identified as An. arabiensis (n = 455/455, 100%). Anopheles pharoensis represented 2.5% (n = 35/1420) of the specimens collected by PSC in Rosso. In Kobeni, An. arabiensis was dominant (n = 278/301, 92.3%) and occurred together with Anopheles coluzzii (n = 18/301, 6%) and An. gambiae (s.s.) (n = 3/301, 1%). Two An. coluzzii × An. arabiensis hybrids were also detected (0.7%) in Kobeni, and An. rufipes was the only other Anopheles species found resting indoors (n = 376/1277, 29.4%). There was an average of 5.6 and 3.6 indoor resting female An. gambiae (s.l.) per room in Kobeni and Rosso, respectively. Indoor resting female An. gambiae (s.l.) mosquitoes in both sites fed most frequently on bovine blood (35.5% in Rosso and 37% in Kobeni). The proportion of An. gambiae (s.l.) mosquitoes that took human blood was significantly higher in Kobeni (HBI = 37%) than in Rosso (HBI = 5.6%) and 32% of An. gambiae (s.l.) mosquitoes contained blood from more than one host species. None of the 1414 tested mosquitoes in both sites were found positive for Plasmodium spp. sporozoites. WHO insecticide resistance tests revealed resistance to permethrin in the An. arabiensis population from Rosso (mortality = 64%) as well as reduced mortality to deltamethrin (mortality = 97%). Conclusion This study provides updated information on the composition and dynamics of the malaria vector system in southern Mauritania where malaria is endemic. Such data are a necessary prerequisite to devise and implement tailored malaria elimination strategies in areas of low residual transmission

Mosquitoes (Diptera: Culicidae) in Mauritania: a review of their biodiversity, distribution and medical importance

International audienceAlthough mosquitoes (Diptera: Culicidae) are important disease vectors, information on their biodiversity in Mauritania is scarce and very dispersed in the literature. Data from the scientific literature gathered in the country from 1948 to 2016 were collected and analyzed. Overall 51 culicid species comprising 17 Anopheles spp., 14 Aedes spp., 18 Culex spp. and two Mansonia spp. have been described in Mauritania among which Anopheles arabiensis, Aedes vexans, Culex poicilipes and Culex antennatus are of epidemiological significance. Anopheles arabiensis is widely distributed throughout the country and its geographic distribution has increased northwards in recent years, shifting its northern limit form 17 degrees 32'N in the 1960s to 18 degrees 47'N today. Its presence in the central region of Tagant highlights the great ecological plasticity of the species. Conversely, the distribution of Anopheles gambiae (s.s.) and Anopheles melas has shrunk compared to that of the 1960s. Anopheles rhodesiensis and An. d'thali are mainly confined in the mountainous areas (alt. 200-700 m), whereas Anopheles pharoensis is widely distributed in the Senegal River basin. Culex poicilipes and Cx. antenattus were naturally found infected with Rift valley fever virus in central and northern Mauritania following the Rift valley outbreaks of 1998 and 2012. Recently, Ae. aegypti emerged in Nouakchott and is probably responsible for dengue fever episodes of 2015. This paper provides a concise and up-to-date overview of the existing literature on mosquito species known to occur in Mauritania and highlights areas where future studies should fill a gap in knowledge about vector biodiversity. It aims to help ongoing and future research on mosquitoes particularly in the field of medical entomology to inform evidence-based decision-making for vector control and management strategies