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).

**
R****EFERENCES**

[1]
**K. PrÃ©vost, 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.