|PORTER, JR., ROBERT|
Submitted to: Journal Of Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/1/1999
Publication Date: N/A
Interpretive Summary: The immune system of the newly hatched chick lacks the ability to fully respond to infections. The current study examined just how well the serum and intestinal immune system in these young birds could respond to an infection by Salmonella enteritidis (SE). We found that challenging birds at this young age results in a long term persistent infection which severely inhibits their immunity - only half of the birds produces detectable antibodies at any one time. This poor response to the infection lasted at least 23 weeks and was observed in both the serum and intestine. Responsiveness to vaccination with inactivated SE or Newcastle disease virus was also reduced which could have serious implications for vaccination regimens currently in place in the field. These results indicate that infection of birds with SE in the hatchery could result in serious problems for the flock and reveal the importance of minimizing the exposure of chicks to SE at this very susceptible period.
Technical Abstract: Newly hatched chicks lack immunological maturity which could compromise their ability to respond to infection by pathogens such as Salmonella enteritidis (SE). A study was conducted where chicks were infected with a sublethal dose of SE at one day post hatch and the systemic and intestinal immune responses to the challenge were followed over time. Birds infected at this age experienced difficulty in clearing the infection and 50 percen of the individuals remained persistently infected out to 23 weeks of age. These birds exhibited only a marginal systemic and mucosal humoral immune response to the infection . No or little response was observed one week post challenge; responses increased somewhat over time. On many of the sampling times, 50 percent or more of the culture-positive birds lacked a detectable plasma &/or intestinal response. Levels of 1,000-100,000 SE/gram feces could be found in the intestines of birds eliciting a good IgA response indicating that, when these birds did respond mucosally, the IgA produced was incapable of clearing the organism once the infection was established. Birds infected at this time period also experienced reduced ability to respond to vaccination. These results demonstrate that exposure of chickens SE early in their life interferes with the ability of these individuals to humorally respond to the infection and to other antigenic stimuli and such effects can be observed over a long time span.