Biology subjects

Bastard, J.

Publications and source records attributed to Bastard, J..

3 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↗

bioRxiv2020

Drivers of ESBL-producing Escherichia coli dynamics in calf fattening farms: a modelling study

The contribution of bacteria in livestock to the global burden of antimicrobial resistance raises concerns worldwide. However, the dynamics of selection and diffusion of antimicrobial resistance in farm animals are not fully understood. Here, we used veal calf fattening farms as a model system, as they are a known reservoir of Extended Spectrum {beta}-Lactamase-producing Escherichia coli (ESBL-EC). Longitudinal data of ESBL-EC carriage and antimicrobial use (AMU) were collected from three veal calf farms during the entire fattening process. We developed 18 agent-based mechanistic models to assess different hypotheses regarding the main drivers of ESBL-EC dynamics in calves. The models were independently fitted to the longitudinal data using Markov Chain Monte Carlo and the best model was selected. Within-farm transmission between individuals and sporadic events of contamination were found to drive ESBL-EC dynamics on farms. In the absence of AMU, the median carriage duration of ESBL-EC was estimated to be 19.6 days (95% credible interval: [12.7; 33.3]). In the best model, AMU was found to influence ESBL-EC dynamics, by affecting ESBL-EC clearance rather than acquisition. This effect of AMU was estimated to decrease gradually after the end of exposure and to disappear after 62.5 days [50.0; 76.9]. Moreover, using a simulation study, we quantified the efficacy of ESBL-EC mitigation strategies. Decreasing ESBL-EC prevalence by 50% on arrival at the fattening farm reduced prevalence at slaughter age by 33.3%. Completely eliminating the use of selective antibiotics had a strong effect on average ESBL-EC prevalence (relative reduction of 79.6%), but the effect was mild if this use was only decreased by 50% compared to baseline (relative reduction of 3.7%).

microbiology↗

bioRxiv2019

Dynamics of Livestock-Associated Methicillin Resistant Staphylococcus aureus in pig farms networks: insight from mathematical modeling and French data

Livestock-associated methicillin resistant Staphylococcus aureus (LA-MRSA) colonizes livestock animals worldwide, especially pigs and calves. Although frequently carried asymptomatically, LA-MRSA can cause severe infections in humans. It is therefore important to better understand LA-MRSA spreading dynamics within pig farms and over pig farms networks, and to compare different strategies of control and surveillance. For this purpose, we propose a stochastic meta-population model of LA-MRSA spread along the French pig-farm network (n=10,542 farms), combining within- and between-farms dynamics, based on detailed data on breeding practices and pig exchanges between holdings. We calibrate the model using French epidemiological data. We then identify farm-level factors associated with the spreading potential of LA-MRSA in the network. We also show that, assuming control measures applied in a limited (n=100) number of farms, targeting farms depending on their centrality in the network is the only way to significantly reduce LA-MRSA global prevalence. Finally, we investigate the scenario of emergence of a new LA-MRSA strain, and find that the farms with the highest indegree would be the best sentinels for a targeted surveillance of such a strains introduction.

microbiology↗