Biology subjects

Chaumeau, V.

Publications and source records attributed to Chaumeau, V..

5 recordsLinked to original sources

bioRxiv2024

Identification of Southeast Asian Anopheles mosquito species with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry using a cross-correlation approach

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) is proposed for mosquito species identification. The absence of public repositories for sharing mass spectra and of open-source data analysis pipelines for fingerprint matching to mosquito species limits widespread use of this technology. The objective of this study was to develop an open-source data analysis pipeline for Anopheles species identification with MALDI-TOF MS. Malaria mosquitos were captured in 33 villages in Karen (Kayin) state in Myanmar. 359 specimens were identified with DNA barcodes and assigned to 21 sensu stricto species and 5 sibling species pairs or complexes. 3584 mass spectra of the head of these specimens identified with DNA barcoding were acquired and the similarity between mass spectra was quantified using a cross-correlation approach adapted from the published literature. A simulation experiment was carried out to evaluate the performance of species identification with MALDI-TOF MS at varying thresholds of cross-correlation index for the algorithm to output an identification result and with varying numbers of technical replicates for the tested specimens, considering PCR identification results as the reference. With one spot and a threshold value of -14 for the cross-correlation index on the log scale, the sensitivity was 0.99 (95%CrI: 0.98 to 1.00), the predictive positive value was 0.99 (95%CrI: 0.98 to 0.99) and the accuracy was 0.98 (95%CrI: 0.97 to 0.99). It was not possible to directly estimate the sensitivity and negative predictive value because there was no true negative in the assessment. In conclusion, the modified cross-correlation approach can be used for matching mass spectral fingerprints to predefined taxa and MALDI-TOF MS is a valuable tool for rapid, accurate and affordable identification of malaria mosquitos.

bioinformatics↗

bioRxiv2024

Identification of Southeast Asian Anopheles mosquito species using MALDI-TOF mass spectrometry

Malaria control in South-East Asia remains a challenge, underscoring the importance of accurately identifying malaria mosquitoes to understand transmission dynamics and improve vector control. Traditional methods such as morphological identification require extensive training and cannot distinguish between sibling species, while molecular approaches are costly for extensive screening. Matrix-assisted laser desorption and ionization time-of-flight mass spectrometry (MALDI-TOF MS) has emerged as a rapid and cost-effective tool for Anopheles species identification, yet its current use is limited to few specialized laboratories. This study aimed to develop and validate an online reference database for MALDI-TOF MS identification of Southeast Asian Anopheles species. The database, constructed using the in-house data analysis pipeline MSI2 (Sorbonne University), comprised 2046 head mass spectra from 209 specimens collected at the Thailand-Myanmar border. Molecular identification via COI and ITS2 DNA barcodes enabled the identification of 20 sensu stricto species and 5 sibling species complexes. The high quality of the mass spectra was demonstrated by a MSI2 median score (min-max) of 61.62 (15.94-77.55) for correct answers, using the best result of four technical replicates of a test panel. Applying an identification threshold of 45, 93.9% (201/214) of the specimens were identified, with 98.5% (198/201) consistency with the molecular taxonomic assignment. In conclusion, MALDI-TOF MS holds promise for malaria mosquito identification and can be scaled up for entomological surveillance in Southeast Asia. The free online sharing of our database on the MSI2 platform represents an important step towards the broader use of MALDI-TOF MS in malaria vector surveillance. Author summaryMosquito-borne diseases like malaria are on the rise globally, and climate change may exacerbate this global threat. Accurate identification of Anopheles mosquitoes, the malaria vectors, is crucial for understanding and controlling the disease. Unfortunately, morphological identification methods require extensive training and molecular methods can be time-consuming, especially when analyzing large samples. In this study, we established a reference database for identifying 25 species of Southeast Asian Anopheles using mass spectrometry, a rapid method based on protein fingerprinting. Using a test panel, we demonstrated the effectiveness of this innovative approach in identifying Southeast Asian Anopheles vectors. Importantly, the online sharing of our database marks an important step towards wider application of the tool, thereby contributing to the global effort to combat malaria.

microbiology↗

bioRxiv2024

Transmission-blocking activity of artesunate, chloroquine and methylene blue on Plasmodium vivax gametocytes.

Plasmodium vivax is now the main cause of malaria outside Africa. The gametocytocidal effects of antimalarial drugs are important to reduce malaria transmissibility, particularly in low transmission settings, but they are not well characterized for P. vivax. The transmission-blocking effects of chloroquine, artesunate and methylene blue on P. vivax gametocytes were assessed. Blood specimens were collected from patients presenting with vivax malaria, incubated with or without the tested drugs, and then fed to mosquitos from a laboratory-adapted colony of Anopheles dirus (a major malaria vector in Southeast Asia). The effects on oocyst and sporozoite development were analyzed under a multi-level Bayesian model accounting for assay variability and the heterogeneity of mosquito Plasmodium-infection. Artesunate and methylene blue, but not chloroquine, exhibited potent transmission-blocking effects. Gametocyte exposures to artesunate and methylene blue reduced the mean oocyst count 469 fold (95%CI: 345 to 650) and 1438 fold (95%CI: 970 to 2064) respectively. The corresponding estimates for the sporozoite stage were a 148 fold reduction (95%CI: 61 to 470) and a 536 fold reduction (95%CI: 246 to 1311) in the mean count, respectively. In contrast, high chloroquine exposures reduced the mean oocyst count by only 1.40 fold (95%CI: 1.20 to 1.64) and the mean sporozoite count 1.34 fold (95%CI: 1.12 to 1.66). This suggests that patients with vivax malaria often remain infectious to anopheline mosquitos after treatment with chloroquine. Immediate initiation of primaquine radical cure or use of artemisinin combination therapies would reduce the transmissibility of P. vivax infections.

microbiology↗

bioRxiv2022

pWCP is a widely distributed and highly conserved Wolbachia plasmid in Culex mosquitoes worldwide

Mosquitoes represent the most important pathogen vectors and are responsible for the spread of a wide variety of poorly treatable diseases. Wolbachia are obligate intracellular bacteria that are widely distributed among arthropods and collectively represents one of the most promising solutions for vector control. In particular, Wolbachia has been shown to limit the transmission of pathogens, and to dramatically affect the reproductive behavior of their host through its phage WO. While much research has focused on deciphering and exploring the biocontrol applications of these WO-related phenotypes, the extent and potential impact of the Wolbachia mobilome remain poorly appreciated. Notably, several Wolbachia plasmids, carrying WO-like genes and Insertion Sequences (IS), thus possibly interrelated to other genetic units of the endosymbiont, have been recently discovered. Here we investigated the diversity and biogeography of the first described plasmid of Wolbachia in Culex pipiens (pWCP) in several islands and continental countries around the world--including Cambodia, Guadeloupe, Martinique, Thailand, and Mexico--together with mosquito strains from colonies that evolved for 2 to 30 years in the laboratory. Together with earlier observation, our results show that pWCP is omnipresent and strikingly conserved among Wolbachia populations within mosquitoes from distant geographies and environmental conditions. These data suggest a critical role for the plasmid in Wolbachia ecology and evolution, and the potential of a great tool for the further genetic dissection or potential manipulation of the endosymbiont.

microbiology↗

bioRxiv2018

Herd protection against Plasmodium falciparum infections conferred by mass antimalarial drug administrations and the implications for malaria elimination

IntroductionAll nations of the Greater Mekong Subregion have committed to elimination of malaria by the year 2030. Elimination efforts rely on increasing access to diagnosis and treatment. However, asymptomatic infections pose a major challenge for these efforts. One approach towards eliminating asymptomatic reservoirs is targeted mass antimalarial drug administration (MDA). Here we present a fine scale spatiotemporal analysis of malaria incidence and prevalence in villages undergoing MDA.\n\nMethodsFour villages along the Myanmar-Thailand border were selected for a MDA pilot study based on clinical records and prevalence surveys. Passive detection of clinical episodes was facilitated through community based malaria clinics in each village. All villagers were screened using venous blood and ultra-sensitive qPCR (uPCR) for detection of parasites at baseline and every subsequent 3 months until month 18 (M18). A final screening was done at M24. MDAs were conducted on M0, M1 and M2 in two villages and on M9, M10, M11 in the remaining two villages. Which villages received early or deferred MDA was decided using restricted randomization. MDA participation, clinical episodes and uPCR detected infections were mapped to participant houses. Scan statistics were used to test for clusters of malaria episodes, malaria infections and non-adherence to MDA. Mixed effects regressions were used to test for risk factors for clinical episodes after MDA.\n\nResultsNeighborhood level MDA adherence was a major predictor for clinical episodes of malaria post-MDA, suggesting a strong herd effect. Each village had a cluster of P. falciparum infections at M0. After M0, there were no clusters of uPCR detectable P. falciparum infections. Clinical episodes of P. falciparum occurred in one village only which had a cluster of non-adherence to MDA and a high mosquito vector human biting rate. Individuals with subclinical P.falciparum infections were more likely to have subsequent clinical episodes than individuals who had no subclinical infections. Individuals who lived in a house with someone who had a clinical episode were more likely to also have a clinical episode subsequently than individuals residing in a house free of P.falciparum infections.\n\nConclusionTo our knowledge this is the first study to show a herd effect from MDA for malaria. These data and results have significance for spatial targeting of interventions for malaria elimination. Clusters of non-adherence to MDA participation can lead to failed elimination if they occur among individuals with asymptomatic infections and given sufficient mosquito vector exposure. Community participation, which can be facilitated through community engagement, is key to MDA success.

epidemiology↗