Changes in Salmonella enteritidis contamination in two layer lines vaccinated during the rearing period

Effect of Salmonella vaccination of breeder chickens on contamination of broiler chicken carcasses in integrated poultry operations

While measures to control carcass contamination with Salmonella at the processing plant have been implemented with some success, on-farm interventions that reduce Salmonella prevalence in meat birds entering the processing plant have not translated well on a commercial scale. We determined the impact of Salmonella vaccination on commercial poultry operations by monitoring four vaccinated and four nonvaccinated breeder (parental) chicken flocks and comparing Salmonella prevalences in these flocks and their broiler, meat bird progeny. For one poultry company, their young breeders were vaccinated by using a live-attenuated Salmonella enterica serovar Typhimurium vaccine (Megan VAC-1) followed by a killed Salmonella bacterin consisting of S. enterica serovar Berta and S. enterica serovar Kentucky. The other participating poultry company did not vaccinate their breeders or broilers. The analysis revealed that vaccinated hens had a lower prevalence of Salmonella in the ceca (38.3% versus 64.2%; P < 0.001) and the reproductive tracts (14.22% versus 51.7%; P < 0.001). We also observed a lower Salmonella prevalence in broiler chicks (18.1% versus 33.5%; P < 0.001), acquired from vaccinated breeders, when placed at the broiler farms contracted with the poultry company. Broiler chicken farms populated with chicks from vaccinated breeders also tended to have fewer environmental samples containing Salmonella (14.4% versus 30.1%; P < 0.001). There was a lower Salmonella prevalence in broilers entering the processing plants (23.4% versus 33.5%; P < 0.001) for the poultry company that utilized this Salmonella vaccination program for its breeders. Investigation of other company-associated factors did not indicate that the difference between companies could be attributed to measures other than the vaccination program.

Salmonella carrier-state in hens: study of host resistance by a gene expression approach

Salmonellosis is one of the main causes of food-borne poisoning due to the consumption of contaminated poultry products. In the flocks, Salmonella is able to persist in the digestive tract of birds for weeks without triggering any symptom. In order to identify molecules and genes involved in the mechanism of host resistance to intestinal carrier-state, two different inbred lines of laying hens were orally inoculated with Salmonella Enteritidis. Bacterial colonization and host gene expression were measured in the caecum and its sentinel lymphoid tissue, respectively. Significantly increased expression of chemokine, anti-infectious cytokine, bacterial receptor, antimicrobial mediator and particularly, defensin genes was observed in the line carrying a lower level of bacteria in the caecum. These innate immunity molecules were either constitutively or inductively highly expressed in resistant adult birds and thus present candidate genes to play an important role in the host defence against Salmonella colonization.