Intervention strategies for Salmonella enteritidis in poultry flocks: a basic approach.

Poultry laying flocks can become infected with Salmonella enteritidis by several routes. In this study a model is presented of the cumulative infection curve of S. enteritidis in laying flocks. Based on this model and practical results the contribution of different routes to the infection can be estimated providing a basis for an effective intervention strategy. For illustration, the cumulative infection curve of S. enteritidis in Dutch laying flocks is analysed. This curve shows a low level of infection at the start of the laying period which indicates that the contribution of the vertical infection route (from infected breeding flocks to progeny) is small. The course of the infection curve indicates that there is a high probability of infection in the first part of the laying period. The result suggests that the laying flocks become infected mainly from the farm environment including not properly cleaned and disinfected poultry houses and infected vermin present on the farm. As a consequence, intervention in The Netherlands should be directed to trace S. enteritidis-contaminated laying farms and eradicate the contamination.