title: Effect of infectious bursal agent on the response of chickens to Newcastle disease and Marek's disease vaccination.
abstract: White Leghorn chickens raised from one day old in an environment contaminated by the infectious bursal agent (IBA) had lower geometric mean titers (GMT) as measured by the hemagglutination-inhibition (HI) test to the Newcastle disease virus (NDV), than control Leghorns reared in an uncontaminated environment. Immunosuppression, defined as a reduction in GMT, was most pronounced at 35-56 days old for Leghorns vaccinated with NDV at 1 and 28 days or at 28 days. In a separate trial with broilers, immunosuppression was similar at 42-56 days old. This study also demonstrated that IBA infection in chickens increased susceptibility to Marek's disease (MD). The unvaccinated control chickens infected with IBA averaged 56.3% MD lesions, whereas unvaccinated controls not exposed to IBA averaged only 18.1% macroscopic lesions. It was also found that 20.7% of the HVT-vaccinated chickens exposed to IBA had gross MD lesions, whereas those HVT-vaccinated chickens reared in an environment free of IBA had 2.99% gross MD lesions.
mesh_terms: D000818:Animals; D002060:Bursa of Fabricius / Q000276:immunology; D002645:Chickens / Q000276:immunology*; D006564:Herpesviridae / Q000276:immunology*; D007165:Immunosuppression Therapy; D007243:Infectious bursal disease virus; D008380:Marek Disease / Q000276:immunology; D009521:Newcastle Disease / Q000276:immunology; D009522:Newcastle disease virus / Q000276:immunology*; D011201:Poultry Diseases / Q000276:immunology*; D012087:Reoviridae; D014422:Turkeys; D014611:Vaccination / Q000662:veterinary