Biology subjects

Girod, R.

Publications and source records attributed to Girod, R..

5 recordsLinked to original sources

bioRxiv2022

Relevance study of vector competence and insecticide resistance in Aedes aegypti laboratory lines

The urban mosquito species Aedes aegypti is the main vector of arboviruses worldwide. Mosquito control with insecticides is the most prevalent method for preventing transmission in the absence of effective vaccines and available treatments; however, the extensive use of insecticides has led to the development of resistance in mosquito populations throughout the world, and the number of epidemics caused by arboviruses has increased. Three mosquito lines with different resistance profiles to deltamethrin were isolated in French Guiana, including one with the I1016 knock-down resistant allele. Significant differences were observed in the cumulative proportion of mosquitoes with a disseminated chikungunya virus infection over time. In addition, certain genes (CYP6BB2, CYP6N12, GST2, trypsin) were variably overexpressed in the midgut at 7 days after an infectious blood meal in these three lines. Therefore, detoxification enzymes and kdr mutations may contribute to an enhanced midgut barrier and reduced dissemination rate. Our work shows that vector competence for chikungunya virus varied between Ae. aegypti laboratory lines with different deltamethrin-resistance profiles. More accurate verification of the functional association between insecticide resistance and vector competence remains to be demonstrated. ImportanceThree Ae. aegypti lines, isolated from the same collection site, underwent different insecticide selection pressures against deltamethrin under laboratory conditions. As a result, they developed different resistant profiles. In this study, when these lines were fed an artificial infectious blood meal containing chikungunya virus, all three lines including the reference strain showed a high infection rate. There was no statistical difference in infection rate found; however, the dissemination rate of the virus from midgut to head were significantly different. A higher resistance level detected by the WHO test was correlated with a lower viral dissemination rate for each strain. This study presented evidence that the insecticide selection pressure or the existence of insecticide resistance could lead to differences in viral dissemination or even transmission in mosquito populations. We hope that our study can give more insights into understanding the roles of mosquito insecticide resistance on viral transmission.

molecular biology↗

bioRxiv2022

Genetic and microbial diversity of the invasive mosquito vector species Culex tritaeniorhynchus across its extensive inter-continental geographic range

Culex (Cx.) tritaeniorhynchus is a mosquito species with an extensive and expanding inter-continental geographic distribution, currently reported in over 50 countries, across Asia, Africa, the Middle East, Europe and now Australia. It is an important vector of medical and veterinary concern, capable of transmitting multiple arboviruses which cause significant morbidity and mortality in human and animal populations. In regions endemic for Japanese encephalitis virus (JEV) in Asia, Cx. tritaeniorhynchus is considered the major vector and this species has also been shown to contribute to the transmission of several other significant zoonotic arboviruses, including Rift Valley fever virus and West Nile virus. Significant variation in vectorial capacity can occur between different vector populations. Obtaining knowledge of a species from across its geographic range is crucial to understanding its significance for pathogen transmission across diverse environments and localities. Vectorial capacity can be influenced by factors including the mosquito genetic background, composition of the microbiota associated with the mosquito and the co-infection of human or animal pathogens. In addition to enhancing information on vector surveillance and potential risks for pathogen transmission, determining the genetic and microbial diversity of distinct populations of a vector species is also critical for the development and application of effective control strategies. In this study, multiple geographically dispersed populations of Cx. tritaeniorhynchus from countries within Europe, Africa, Eurasia and Asia were sampled. Molecular analysis demonstrated a high level of genetic and microbial diversity within and between populations, including genetic divergence in the mosquito CO1 gene, as well as diverse microbiomes identified by 16S rRNA gene amplicon sequencing. Evidence for the detection of the endosymbiotic bacteria Wolbachia in some populations was confirmed using Wolbachia-specific PCR detection and sequencing of Wolbachia MLST genes; in addition to PCR-based detection of insect-specific viruses. Laboratory vector competence showed Cx. tritaeniorhynchus from a Greek population are likely to be competent vectors of JEV. This study expands understanding of the diversity of Cx. tritaeniorhynchus across its inter-continental range, highlights the need for a greater focus on this invasive vector species and helps to inform potential future directions for development of vector control strategies.

genetics↗

bioRxiv2022

Decoding rRNA Sequences for Improved Metagenomics in Sylvatic Mosquito Species

As mosquito-borne virus epidemics are often preceded by undetected spillover events, surveillance and virus discovery studies in non-urban mosquitoes informs pre-emptive and responsive public health measures. RNA-seq metagenomics is a popular methodology but it is constrained by overabundant rRNA. The lack of reference sequences for most mosquito species is a major impediment against physical and computational removal of rRNA reads. We describe a strategy to assemble novel rRNA sequences from mosquito specimens, producing an unprecedented dataset of 234 full-length 28S and 18S rRNA sequences of 33 medically important species from countries with known histories of mosquito-borne virus circulation (Cambodia, the Central African Republic, Madagascar, and French Guiana). We also evaluate the utility of rRNA sequences as molecular barcodes relative to the mitochondrial cytochrome c oxidase I (COI) gene. We show that rRNA sequences can be used for species identification when COI sequences are ambiguous or unavailable, revealing evolutionary relationships concordant with contemporary mosquito systematics. This expansion of the rRNA reference library improves mosquito RNA-seq metagenomics by permitting the optimization of species-specific rRNA depletion protocols for a broader species range and streamlined species identification by rRNA barcoding. In addition, rRNA barcodes could serve as an additional tool for mosquito taxonomy and phylogeny.

bioinformatics↗

bioRxiv2021

Differential transcriptomic response of Anopheles arabiensis to Plasmodium vivax and Plasmodium falciparum infection

Plasmodium vivax malaria is now recognized as the second most dangerous parasitic threat to human health with the regular decrease of Plasmodium falciparum worldwide over recent decades. A very limited numbers of studies address the interaction of P. vivax with its Anopheles mosquito vectors. Those studies were conducted in P. vivax endemic countries with P.vivax local major vectors for which limited genomic and genetic tools are available. Despite the presence of P. vivax in several African countries and increasing reports on its occurrence in many others, there is virtually no data on the molecular responses of Anopheles arabiensis, a major African mosquito vector, to P. vivax, which limits the development of further "mosquito-targeted" interventions aimed at reducing P. vivax transmission. Taking advantage of the situation of Madagascar where P. falciparum, P. vivax and An. arabiensis are present, we explore the molecular responses of An. arabiensis towards these two human malaria parasites. RNA sequencing on RNAs isolated from mosquito midguts dissected at the early stage of infection (24 hours) was performed using mosquitoes fed on the blood of P. vivax and P. falciparum gametocyte carriers in a field station. From a de novo assembly of An. arabiensis midgut total RNA transcriptome, the comparative analysis revealed that a greater number of genes were differentially expressed in the mosquito midgut in response to P. vivax (209) than to P. falciparum (81). Among these, 15 common genes were identified to be significantly expressed in mosquito midgut 24 hours after ingesting P. vivax and P. falciparum gametocytes, including immune responsive genes and genes involved in amino-acid detoxification pathways. Importantly, working with both wild mosquitoes and field circulating parasites, our analysis revealed a strong mosquito genotype by parasite genotype interaction. Our study also identified 51 putative long non-coding RNAs differentially expressed in An. arabiensis mosquito infected midgut. Among these, several mapped to the published An. arabiensis genome at genes coding immune responsive genes such as gambicin 1, leucine-rich repeat containing genes, either on sense or antisense strands. This study constitutes the first comparison of An. arabiensis molecular interaction with P. vivax and P. falciparum, investigating both coding and long non-coding RNAs for the identification of potential transcripts, that could lead to the development of novel approaches to simultaneously block the transmission of vivax and falciparum malaria.

microbiology↗

bioRxiv2020

Variation in pyrethroid resistance phenotypes in Anopheles darlingi from residual malaria transmission area: warning on suspected resistance built-up in French Guiana.

Anopheles darlingi is the major vector of malaria in South America. In French Guiana, malaria transmission occurs inland and along the rivers with a particular reemergence in the lower Oyapock area. Control against malaria vector is performed using deltamethrin indoor residual spraying and long lasting impregnated bednets. For four years, the level of resistance to pyrethroids was monitored using CDC bottle tests in An. darlingi populations. Resistance built-up was suspected in a mosquito population in malaria endemic area but did not sustained, supposably due to the reintroduction of susceptible alleles. No mutation on the insecticide target genes was found, metabolic resistance is then suspected.

zoology↗