Biology subjects

Chevalier, V.

Publications and source records attributed to Chevalier, V..

4 recordsLinked to original sources

bioRxiv2025

Quantitative evaluation of dogs as sentinels for Rift Valley fever virus circulation in Madagascar

Sentinel animals may play a key role in surveillance of zoonotic arbovirus circulation, particularly in developing countries with low levels of investment in health. This study aimed to assess the relevance of using dogs as sentinel animals for Rift Valley fever virus (RVFV) surveillance in Madagascar. Serological surveys were conducted on 513 dogs and 135 cattle in the Ifanadiana district. In addition, 486 human dry blood samples available from the same area were used. Serostatus against RVFV was determined using a competitive Enzyme-Linked Immunosorbent Assay (cELISA) for dog and cattle samples, and a Multiplex Bead Assay (MBA) for human samples. Serocatalytic models fitted to age-stratified serological data were developed to estimate the RVF force of infection (FOI) under several hypotheses, ranging from no relationship to proportional FOIs between humans, cattle, and dogs. Antibodies to RVFV were detected in 23 of 513 dogs (4.5%; 95% confidence interval (95% CI): [2.9 - 6.7]), in 86 of 486 humans (17.7%; 95% CI: [14.4 - 21.4]), and in 33 of 135 cattle (24.4%; 95% CI: [17.5 - 32.6]). Based on the deviance information criterion, the best supported model indicated that FOI in humans and cattle was proportional to FOI in dogs. Proportionality parameters were estimated at 2.6 (95% credible interval (95% CrI): [1.4 - 5.1]) for humans and 3.5 (95% CrI: [1.3 - 6.4]) for cattle. Our findings suggest that sampling dogs could be used to identify RVFV circulation in endemic areas, and infer the exposure of humans and cattle in these areas in Madagascar. This original result paves the way for an innovative surveillance method for RVFV in Madagascar and other endemic countries, but also for other arboviruses such as West Nile virus. Author SummaryRift Valley fever (RVF) is a viral zoonosis transmitted by mosquitoes and through contact with the blood, tissues or body fluids of infected animal. The disease has caused at least three major epidemics in Madagascar to date. RVF mainly affects ruminants through abortion and high mortality rate in young animals, and a range of influenza-like to more severe syndromes that can lead to death in some cases in humans. Dogs that interact with humans and are exposed to mosquito bites in the same environment may not develop clinical signs or sufficient viremia to infect vectors, but they could still develop an immune response when exposed to RVF virus (RVFV). This study aimed to assess the relevance of using dogs as sentinel animals for RVFV circulation on the island. Serocatalytic models were developed using serological data to represent and quantify the relationships between the force of infection (FOI) of RVFV exerted on dogs, humans and cattle. We found a proportional relationship between the FOI exerted on dogs and that exerted on humans and cattle. These findings support the relevance of using dogs as sentinel animals for monitoring the circulation of RVFV and arboviruses in general.

pathology↗

bioRxiv2025

Characterization and evolutionary history of novel SARS-CoV-2-related viruses in bats from Cambodia

Circulating bat coronaviruses present a significant pandemic threat, yet our understanding of their genetic diversity and evolutionary dynamics remains limited. Over 3 years, we sampled 1,462 bats in Cambodias Steung Treng province, identifying extensive and diverse coronaviruses co-circulation. Using metatranscriptomic and amplicon sequencing, we generated 33 complete sarbecovirus genomes, revealing novel lineages that cluster into four distinct groups, each associated with different Rhinolophus bat species. Our analysis highlights rapid migration and recombination of sarbecovirus lineages over short distances and timescales. Of note, the receptor-binding domains of two novel viral groups exhibit high similarity to SARS-CoV-2, and pseudovirus assays confirmed the ability of this spike protein to mediate entry into cells expressing human ACE2, suggesting a potential zoonotic risk. The observed genetic diversity underscores the urgent need for continuous surveillance to identify high-risk animal-to-human interfaces and inform pandemic preparedness.

microbiology↗

bioRxiv2019

Rift Valley fever in northern Senegal : a modelling approach to analyse the processes underlying virus circulation recurrence

Rift Valley fever (RVF) is endemic in northern Senegal, a Sahelian area characterized by a temporary pond network that drive both RVF mosquito population dynamics and nomadic herd movements. To investigate the mechanisms that explain RVF recurrent circulation, we modelled a realistic epidemiological system at the pond level integrating vector population dynamics, resident and nomadic ruminant herd population dynamics, and nomadic herd movements recorded in Younoufere area [1]. To calibrate the model, serological surveys were performed in 2015-2016 on both resident and nomadic herds in the same area. Mosquito population dynamics were obtained from a published model trained in the same region [2]. Model comparison techniques were used to compare five different scenarios of virus introduction by nomadic herds associated or not with vertical transmission in Aedes vexans. Our serological results confirmed a long lasting RVF endemicity in resident herds (IgG seroprevalence rate of 15.3%, n=222), and provided the first estimation of RVF IgG seroprevalence in nomadic herds in West Africa (12.4%, n=660). Multivariate analysis of serological data suggested an amplification of the transmission cycle during the rainy season with a peak of circulation at the end of that season. The best scenario of virus introduction combined yearly introductions of RVFV from 2008 to 2015 (the study period) by nomadic herds, with a proportion of viraemic individuals predicted to be larger in animals arriving during the 2nd half of the rainy season (3.4%). This result is coherent with the IgM prevalence rate (4%) found in nomadic herds sampled during the 2nd half of the rainy season. Although the existence of a vertical transmission mechanism in Aedes cannot be ruled out, our model demonstrates that nomadic movements are sufficient to account for this endemic circulation in northern Senegal. Author summaryRift Valley fever (RVF) is one of the most important vector borne disease in Africa, seriously affecting the health of domestic ruminants and humans and leading to severe economic consequences. This disease is endemic in northern Senegal, a Sahelian area characterized by a temporary pond network that drive both RVF mosquito population dynamics and nomadic herd movements. Two non-exclusive mechanisms may support this endemicity: recurrent introductions of the virus by nomadic animals, and vertical transmission of the virus (i.e. from infected female mosquito to eggs) in local Aedes populations. The authors followed up during 1 year resident and nomadic herds. They used the data thus obtained to model a realistic epidemiological system at the pond level integrating vector population dynamics, resident and nomadic ruminant herd population dynamics. They found that the best scenario explaining RVF remanence combined yearly introductions of RVFV by nomadic herds, with a proportion of viraemic predicted to be larger in animals arriving during the 2nd half of the rainy season, which is consistent with an amplification of virus circulation in the area during the rainy season. Although the existence of a vertical transmission mechanism in Aedes cannot be ruled out, their results demonstrates that nomadic movements are sufficient to account for this endemic circulation in northern Senegal.

ecology↗

bioRxiv2018

Modelling and assessment of combining gilt vaccination, vector control and pig herd management to control Japanese Encephalitis virus transmission in Southeast Asia

Despite existence of human vaccines, Japanese Encephalitis (JE) remains a prominent public health problem in Southeast Asia (SEA). JE is caused by a Flavivirus which is transmitted between pigs, the main amplifying hosts, by Culex mosquito bites. Therefore, sow vaccination, pig herd management and vector control -or a combination of these three potential control measures, might constitute additional control measures contributing to reduce JE health impact in humans, and economic losses in pig farms. We built a deterministic metapopulation model, combining a pig and a Culex mosquito vector population, to represent JE virus (JEV) transmission dynamic within a pig herd. The dynamic of the epidemiological systems resulted from an infectious process, operating in continuous time, combined with the pig breeding process that was modeled based on discrete events occurring instantaneously. We used this model to simulate JEV transmission within a continuum of plausible pig breeding systems encountered in SEA, ranging from backyards to semi-commercial systems. We then analyzed the joint effects of the three tested control measures, namely sow vaccination, pig herd management and vector control, on several indicators characterizing (i) the ability of different pig breeding systems to be simultaneously profitable and allow JEV eradication in the herd, (ii) the impact of JE on pig production and the profitability of gilt vaccination, and (iii) the risk for human beings living in the vicinity of pig herds and/or near pig slaughterhouses. According to our model, herd management has no effect on JEV circulation. Vector control alone is a major control tool but shows paradoxical effects that should be considered in any mosquito based control strategy. Combining sow vaccination and vector control could be an alternative or an additional measure to human vaccination to efficiently reduce both JE incidence in humans and the economic impact of JE infection on pig farms.\n\nAuthor summaryJapanese Encephalitis (JE) still has an important impact on human health in Southeast Asia. Human vaccination is an efficient tool to protect humans but it may not be effective against emerging strains, and poor or remote population may not be able to afford it. Severe outbreaks still occur. JE virus (JEV) is primarily transmitted between pigs and mosquitoes. When infected after sexual maturity, pigs show reproduction disorders leading to economic losses. We propose a modelling approach to investigate the joint effect of three additional control measures, namely sow vaccination, vector control, and pig herd management on JEV transmission dynamic, risk for humans and pigs, and pig breeding sustainability. According to our results, vector control, associated or not with sow vaccination, may be an efficient tool to reduce JE incidence in both human and pigs.

epidemiology↗