Risk of Salmonella introduction at dairy farms caused by Dutch wildlife.

Abstract

To maintain the high quality of their dairy products, Dutch farmers are required to produce Salmonella-free milk. Wildlife introduction is one of several ways to introduce a Salmonella-infection on a dairy farm. Because of the lack of Salmonella¬-prevalence studies in Dutch wildlife, the present study observes Salmonella prevalence in Salland, the Netherlands. 121 animals were collected from and near dairy farms in Salland, from which two Salmonella-positive samples were obtained from two rats. The study also included 25 rats from two different dumpsites near the region of Salland, which were all Salmonella-free. While the present study has a sufficient number of samples per km2, the sample pool is less representative of real-life wildlife diversity. To estimate the risk wildlife presents for dairy farms, different animal groups have been investigated. For dairy farms in Salland, the biggest risk for Salmonella-introductions are presented by carrion birds and gulls, followed by large flocks of small garden birds. A special case can be made for rats and mice, that rarely introduce Salmonella themselves. Instead, they could maintain the on-farm infection as reservoirs, similar to cats and dogs. Other species, like raptors, carnivores, deer, and wild boars are considered low-risk. Finally, the risk presented by moles, hares, and wild rabbits is uncertain.