title: Serological responses to Mycoplasma synoviae in chickens infected with virulent or avirulent strains of Marek's disease virus.
abstract: The pathogenicity and immunosuppressive capability of five strains of Marek's disease herpesvirus (MDHV) was examined. Three of the strains (ALA, MISS, NCS) were isolated from flocks experiencing vaccine breaks while the other two strains (GA, HN) represented prototype virulent and avirulent viruses. Pathogenicity of MDHV strains was evaluated on their ability to cause mortality, their ability to cause gross or microscopic lesions, and the median latent period to death (MLPD) for each strain. Antibody responses to Mycoplasma synoviae (MS) were tested by the serum plate agglutination and hemagglutination inhibition tests. Chicks infected with the virulent strains of MDHV had greater mortality, greater lesion incidence, and shorter MLPD that did chicks infected with the avirulent HN strain. Infection with virulent strains reduced the antibody response to MS and caused severe bursal lesions. Chicks infected with the avirulent HN strain exhibited a slight immunosuppression, but they had no evidence of bursal destruction.
mesh_terms: D000818:Animals; D002645:Chickens / Q000276:immunology*; D005856:Germ-Free Life; D008381:Herpesvirus 2, Gallid / Q000276:immunology*; D009175:Mycoplasma Infections / Q000276:immunology / Q000662:veterinary*; D011201:Poultry Diseases / Q000276:immunology*