A model of Salmonella infection within industrial house hens

Effect of genetic resistance of the hen toSalmonellacarrier-state on incidence of bacterial contamination: synergy with vaccination

“…Indeed, Protais et al [9] observed large differences when comparing poultry lines inoculated at the same time and with the same dose of inoculation. The model derived by Prévost et al [7] may be used for such data: since each line was reared separately, it was possible to process one subpopulation at a time. However, that is not the most general case, especially since genetics is partly involved in the control of the hens' rate of infection [2].…”

“…However, that is not the most general case, especially since genetics is partly involved in the control of the hens' rate of infection [2]. The model developed by Prévost et al [7] was therefore extended to fit the heterogeneity of the degree of resistance within a population. Theoretical results showed that, as it was the case in a homogenous population [7], the existence of an equilibrium is dependant on the reproductive number R 0,p , that is the number of secondary Salmonella infections generated by an infected animal.…”

“…The model described in Prévost et al [7] was implemented with two subpopulations that have different genetic values. We denote by N the total number of hens (thereafter assumed to be constant in time) and N 1 and N 2 the number of hens in the two subpopulations such that N = N 1 + N 2 .…”

“…Since the different parameters of the model are described in [7], here we will only give a brief description of them. Within each subpopulation (i = 1, 2): -κ i : is the exposition rate which modulates the transmission of the infection, -g i : the rate of translocation of the digestive barrier, -η i : the recovery rate, which depends on innate and acquired immunity leading to bacterial clearance, -ν i : the rate of return of recovered hens to the susceptible S status, -λ : the rate of natural mortality of Salmonella in the hen house, -β Ei : the rate of bacterial excretion by hens suffering from digestive contamination, -β Ii : the rate of bacterial excretion by hens suffering from systemic contamination.…”

“…But none of them are able to assure zero risk of animal contamination and human transmission, at least when used alone. In a previous study [7,8], we derived mathematical models for Salmonella transmission and used them to identify the most important factors of variation of egg contamination rate and thus of risk of human contamination. More precisely, we built a mathematical model to assess Salmonella dissemination within the flock.…”