Salmonella Project 

 

The MATLAB Code for an IBM model will be available soon

 

 

    Salmonella is one of the major sources of toxi-infections in Humans. The association between egg consumption and Salmonella outbreaks is a serious economic and public health problem. To control the incidence of Salmonella in poultry flocks, many prophylactic means have been developed but none allows a total reduction of the risk.

 

                                                                                                

 

    Our goal is to derived models for Salmonella transmission and used them to appreciate the most important factors of variation of egg contamination rate and thus of risk of human contamination [1,3].  Recently, we have shown that  mixing, animals issued from a line selected for a lower (denoted Sal-) or higher propensity to carry Salmonella (denoted Sal+) results in a reduction of the maximal percentage of contaminated animals but doesn't accelerate the extinction of the disease. We have also observed that vaccination and selection should be synergic, since a former contamination reduces the maximal prevalence [2]. These results show that  the interest in the introduction, even at a rather moderate percentage, of animals selected for a reduced rate of Salmonella carrier-state within commercial flock.

 

 

 

 

    Figure 1: This figure corresponds to the production of contaminated eggs. In this figure the crosses represent real data coming from experiments, and the red curve corresponds to the numerical simulation of the model in [1].

 

 

 

    Now, we interest to improve the modelisation of Salmonella infection by introducing the evolution of the bacterial load at the individual level. More precisely, we want to see the role of the immune response on the propagation of the epizooty.  Two models are considered: one deterministic and one Individual Based Model.  The main objective of this work is to construct a visual tool in order to view how the epizooty evolves over time in the flock. (see the following simulation).

 

   

 

 

               

Click here to see numerical simulation of a Salmonella infection in a hens house

 

       

           

In this movie on the left hand side we use the colors below to represent the infection status of hens in the cages

 

 

           

                                              Susceptible  

 

                                              Digestive infection

 

                                              Systemic infection

 

                                              Recovered

                      

 

On the right side figure we represent the density of bacteria in the environment (i.e. in the hen?s house).                                                                                                                                                                                                                                                                                                                    

REFERENCES                                                                         

      

[1] K. Prévost, P. Magal, J. Protais and C. Beaumont (2008), Effect of hens? genetic resistance to Salmonella carrier-state on incidence of bacterial contamination: synergy with vaccination, Veterinary Research 39:20.                                                          

[2] K. Prevost, C. Beaumont, P. Magal (2007), Asymptotic behavior in a Salmonella Infection Model,  Mathematical Modelling of Natural Phenomena, 2, 1, 1-22.                                                                                                     

[3] K. Prevost, C. Beaumont, P. Magal (2006), A Model of Salmonella infection within hens herd. Journal of Theoretical Biology 242, 755?763.