A MULTI-SCALE EPIDEMIC MODEL OF SALMONELLA INFECTION WITH HETEROGENEOUS SHEDDING

Salmonella strains colonize the digestive tract of farm livestock, such as chickens or pigs, without affecting them, and potentially infect food products, representing a threat for human health ranging from food poisoning to typhoid fever. It has been shown that the ability to excrete the pathogen in the environment and contaminate other animals is variable. This heterogeneity in pathogen carriage and shedding results from interactions between the host's immune response, the pathogen and the commensal intestinal microbiota. In this paper we propose a novel generic multiscale modeling framework of heterogeneous pathogen transmission in an animal population. At the intra-host level, the model describes the interaction between the commensal microbiota, the pathogen and the inflammatory response. Random fluctuations in the ecological dynamics of the individual microbiota and transmission at between-host scale are added to obtain a drift-diffusion PDE model of the pathogen distribution at the population level. The model is further extended to represent transmission between several populations. The asymptotic behavior as well as the impact of control strategies including cleaning and antimicrobial administration are investigated through numerical simulation. Resume. Les salmonelles colonisent le tube digestif des animaux d'elevage, comme les poulets ou les porcs, sans les affecter, et peuvent infecter les productions alimentaires. Elles constituent une menace pour la sante humaine allant de l'intoxication alimentairea la fievre typhoide. Il aete demontre que la capacitea excreter le pathogene dans l'environnement et contaminer d'autres animaux est variable. Cette heterogeneite dans le portage et l'excretion du pathogene resulte des interactions entre la reponse immunitaire de l'hote, le pathogene et le microbiote intestinal commensal. Dans cet article, nous proposons un nouveau cadre generique de modelisation multi-echelle de la transmission heterogene d'un pathogene dans une population animale. Au niveau intra-hote, le modele decrit l'interaction entre le microbiote commensal, le pathogene et la reponse inflammatoire. L'ajout de fluctuations aleatoires dans la dynamiqueecologique du microbiote des individus et d'une transmissiona l'echelle inter-individuelle permet d'obtenir un modele EDP de transport-diffusion de la distribution des pathogenesa l'echelle de la population. Le modele est encoreetendu pour representer la transmission entre plusieurs populations. Le comportement asymptotique ainsi que l'impact des strategies de controle,comprenant la desinfection de l'environnement et l'administration d'antimicrobiens, sontetudies par simulation numerique.