Modelling <em>Salmonella</em> spread in a pig farm under three biosecurity strategies

National audiencePork products contribute to human cases of salmonellosis. The Salmonella contamination level of pigs at slaughter age is a critical point in the contamination of the human food chain. Our aim here is therefore to assess this risk by estimating the prevalence in those pigs. The propagation of Salmonella occurs within and between pig herds, but we first chose to concentrate on the farm level. At this level, recommendations to reduce Salmonella transmission were determined from previously identified risk factors. However, the efficiency of these measures has not yet been evaluated. A stochastic mathematical model was hence developed to simulate the pig population dynamics and pathogen transmission within a French farrow-to-finish herd in order to test different management options. We considered the producers’ measures that influence the contact structure and the direct and indirect transmission of Salmonella. A particular attention was paid to (i) the composition and housing of pig batches (strictly separate batches to loose batch mixing) and (ii) hygienic control measures (all-in-all-out, cleaning, disinfection). The proportion of pigs at slaughter age either carrying or shedding Salmonella was obtained under different management strategies. The effects of control measures were described depending on whether these actions were implemented separately or combined