Mechanisms of action of nutritional tools to control intestinal zoonotic pathogens

Poultry can carry different zoonotic pathogens in their intestinal tract, including Salmonella and Campylobacter. Recent E.U. regulations constitute an incentive for the poultry producers to take measures aiming at reducing the degree of contamination in the live birds. Moreover, for Salmonella national control plans are implemented. Many different tools are available that can help reducing the level of contamination. Among these tools, numerous feed additives are on the market for which a claim is made with respect to reduction of carriage of Salmonella and other zoonotic agents. Most of these additives can be classified as prebiotics, probiotics, synbiotics, short chain fatty acids or mixtures of natural plant extracts. Most claims are based on trial and error experiments. In recent years however, both in vivo and in vitro experiments have provided a better understanding of the pathogenesis of the carrier state in chickens infected with different zoonotic agents. Simultaneously, insight has grown in specific and non-specific protection mechanisms in the chicken intestinal tract. By combining new information on the intestinal mucosal barrier with new data on pathogenesis of the infections, a rational explanation can be provided for the activity of certain feed additives. Some of the newly discovered mechanisms appear to be generic. Therefore in the near future it may be possible to exploit and to steer these intestinal mucosal protection mechanisms.