Pathogenesis of Newcastle Disease in Vaccinated Chickens: Pathogenicity ofIsolated Virus and Vaccine Effect on Challenge of Its Virus

[摘要] References(19)Cited-By(1)The pathogenicity of Newcastle disease (ND) virus, isolated from ND outbreak invaccinated chickens, was evaluated through experiments. The pathogenicity indexes (meandeath time (MDT); 58 hr, intracerebral pathogenicity index (ICPI); 1.7 and intravenouspathogenicity index (IVPI); 2.51) indicated that the ND virus was velogenic. The ND viruscaused lymphocytic necrosis in the spleen with fibrinous exudation and proliferation ofmacrophages, sinusoidal fibrin exudation in the liver, proliferation of macrophages in thelung, lymphocytic necrosis and depletion in the bursa of Fabricius, cecal tonsils andthymus, necrosis of bone marrow, tracheitis, conjunctivitis and necrosis of featherepithelial cells in specific-pathogen-free chickens. Immunohistochemically, ND virusantigens were seen in the lesions mentioned above. The ND virus could not induce theencephalitis and pancreatitis that were observed in the natural case of ND in vaccinatedchickens. There was no clinical disease in vaccinated chickens after the challenge of theND virus. In diluted ND vaccine experiments, chickens vaccinated with a high dilution ofvaccine and then challenged with the ND virus showed clinical sign and mortality withpancreatic focal necrosis. Vaccine diluted with fresh tap water had no effect onprotection against the challenge of the ND virus. This study suggests that impropervaccination may be involved in outbreaks of ND in vaccinated chickens.

[学科分类] 兽医学

[关键词] Newcastle disease;pathogenesis;specific-pathogen-free chicken;vaccinated chicken