Levels of insecticide resistance to deltamethrin,malathion,and temephos,and associated mechanisms in Aedes aegypti mosquitoes from the Guadeloupe and Saint Martin islands(French West Indies)

Background:In the Guadeloupe and Saint Martin islands,Aedes aegypti mosquitoes are the only recognized vectors of dengue,chikungunya,and Zika viruses.For around 40 years,malathion was used as a mosquito adulticide and temephos as a larvicide.Since the European Union banned the use of these two insecticide molecules in the first decade of the 21st century,deltamethrin and Bacillus thuringiensis var.israelensis are the remaining adulticide and larvicide,respectively,used in Guadeloupe.In order to improve the management of vector control activities in Guadeloupe and Saint Martin,we investigated Ae.aegypti resistance to and mechanisms associated with deltamethrin,malathion,and temephos.Methods:Ae.aegypti mosquitoes were collected from six different localities of Guadeloupe and Saint Martin.Larvae were used for malathion and temephos bioassays,and adult mosquitoes for deltamethrin bioassays,following World Health Organization recommendations.Knockdown resistance(Kdr)genotyping for V1016I and F1534C mutations,and expression levels of eight enzymes involved in detoxification mechanisms were examined in comparison with the susceptible reference Bora Bora strain.Results:Resistance ratios(RR50)calculated for Ae.aegypti larvae showed high resistance levels to temephos(from 8.9 to 33.1-fold)and low resistance levels to malathion(from 1.7 to 4.4-fold).Adult females displayed moderate resistance levels to deltamethrin regarding the time necessary to affect 50%of individuals,varying from 8.0 to 28.1-fold.Molecular investigations on adult mosquitoes showed high resistant allele frequencies for V1016I and F1534C(from 85 to 96%and from 90 to 98%,respectively),as well as an overexpression of the glutathione S-transferase gene,GSTe2,the carboxylesterase CCEae3a,and the cytochrome genes 014614,CYP6BB2,CYP6M11,and CYP9J23.Conclusions:Ae.aegypti populations from Guadeloupe and Saint Martin exhibit multiple resistance to organophosphates(temephos and malathion),and pyrethroids(deltamethrin).The mechanisms associated with these resistance patterns show strong frequencies of F1534C and V1016I Kdr mutations,and an over-expression of CCEae3a,GSTe2,and four cytochrome P450 genes(014614,CYP9J23,CYP6M11,CYP6BB2).These results will form the baseline for a deeper understanding of the insecticide resistance levels and associated mechanisms of Ae.aegypti populations and will be used to improve vector control strategies in Guadeloupe and Saint Martin.

Impact of past and on-going changes on climate and weather on vector-borne diseases transmission:a look at the evidence

Background:The climate variables that directly influence vector-borne diseases'ecosystems are mainly temperature and rainfall.This is not only because the vectors bionomics are strongly dependent upon these variables,but also because most of the elements of the systems are impacted,such as the host behavior and development and the pathogen amplification.The impact of the climate changes on the transmission patterns of these diseases is not easily understood,since many confounding faaors are acting together.Consequently,knowledge of these impacts is often based on hypothesis derived from mathematical models.Nevertheless,some direct evidences can be found for several vector-borne diseases.Main body:Evidences of the impact of climate change are available for malaria,arbovirus diseases such as dengue,and many other parasitic and viral diseases such as Rift Valley Fever,Japanese encephalitis,human African trypanosomiasis and leishmaniasis.The effect of temperature and rainfall change as well as extreme events,were found to be the main cause for outbreaks and are alarming the global community.Among the main driving factors,climate strongly influences the geographical distribution of insect veaors,which is rapidly changing due to climate change.Further,in both models and direct evidences,climate change is seen to be affecting veaor-borne diseases more strikingly in fringe of different climatic areas often in the border of transmission zones,which were once free of these diseases with human populations less immune and more receptive.The impact of climate change is also more devastating because of the unpreparedness of Public Health systems to provide adequate response to the events,even when climatic warning is available.Although evidences are strong at the regional and local levels,the studies on impact of climate change on vector-borne diseases and health are producing contradictory results at the global level.Conclusions:In this paper we discuss the current state of the results and draw on evidences from malaria,dengue and other vector-borne diseases to illustrate the state of current thinking and outline the need for further research to inform our predictions and response.