Investigation into resistance to experimental Salmonella challenge in neonatal leghorn chickens

Abstract

The purpose of the following studies was to investigate selected mechanisms of resistance to Salmonella typhimurium or S. enteritidis experimental challenge in neonatal Leghorn chickens. Immunoprophylaxis of Salmonella infections in poultry through the administration of recently characterized avian cytokines may represent a viable means of controlling Salmonella in commercial poultry flocks. In the present investigation, we evaluated two recently characterized avian cytokines, Salmonella enteritidis-immune lymphokine (SE-ILK) or recombinant turkey interferon gamma (rtIFNγ), for efficacy in protecting neonatal Leghorn chickens from experimental Salmonella challenge. Additionally, our laboratories have observed a seasonal pattern of apparent maternal-associated protection in Leghorn chickens which occurs naturally in the state of Texas during the warmer months of the year. We hypothesized that a potential heat-stress associated maternal factor, which improves innate mechanisms of resistance to invasive Salmonella challenge, may be transmitted vertically from hen to progeny, and tested this hypothesis experimentally in the present investigation. To evaluate the potential protective effect of the in ovo, oral, or intraperitoneal (IP) administration of SE-ILK in neonatal Leghorn chickens against S. typhimurium colonization, chicks were challenged with S. typhimurium at selected times post-SE-ILK administration, and estimates of cecal colonization were obtained by collecting cecal contents and enumerating viable S. typhimurium. While data obtained in the present experiments were variable, suggestion of the ability of SE-ILK to protect chicks against S. typhimurium colonization was observed in two experiments. When the administration of rtIFNγ to Leghorn chicks was evaluated for potential protection against invasive S. enteritidis challenge, a consistent pattern of protection was observed. In three independent experiments, significant (P<0.05) protection against internal organ invasion in Leghorn chicks was observed when the IP administration of rtIFNγ preceded S. enteritidis experimental challenge. To investigate the observed apparent heat-stress associated maternal mechanism of resistance in neonatal Leghorn chickens, we reared adult breeding hens under elevated environmental temperatures and measured resistance of progeny to S. enteritidis challenge. Results obtained from the present experiments did not identify a degree of resistance in progeny obtained from heat-stressed hens, as susceptibility to experimental S. enteritidis challenge was not different in progeny from heat-stressed or control hens.