Immunological and genetic aspects of resistance to Salmonella in broilers

Abstract

Salmonella can be a threat for both public health and economy. Salmonellosis is one of the most common food-borne diseases in human. The economical problems in the poultry industry are caused by treatment of the infection, and the infection might lead to high levels of mortality of the flock. Moreover, the infection might lead to decreased animal welfare. To prevent these infections, and their consequences in chicken, birds can be vaccinated or treated with antibiotics. However, the use of antibiotics and vaccines has been criticized because of the possible development of antibiotic resistant bacteria and the potential dangers of antibiotic and vaccine residues in animal-derived food products. A solution to those issues could be the enhancement of natural genetic resistance, by improving the reaction of the host to a pathogen. This can be accomplished e.g. when the immune response of poultry can be enhanced. Research described in this thesis, provides insight on the differences in immune responses between chickens and within chicken lines in relation to disease resistance. Results of in vitro and in vivo studies showed, that the innate immune response played an important role in chickens in relation to natural and disease resistance. Furthermore, several genes were identified that were associated with Salmonella resistance in chicken. Overall, this study confirmed that disease resistance to Salmonella is a polygenic trait, which makes it difficult to apply in breeding strategies. However, together with other strategies to control Salmonella that already exist, the genetic approach may provide additional means to reduce the transmission of the infection and control Salmonella.