Pathogenicity of recent isolates of infectious bursal disease virus in specific-pathogen-free chickens: protection conferred by an intermediate vaccine strain |
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Authors: | A G Rosales P Villegas P D Lukert O J Fletcher M A Mohamed J Brown |
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Affiliation: | Department of Avian Medicine, College of Veterinary Medicine, University of Georgia, Athens 30602. |
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Abstract: | The pathogenicity of recent isolates of infectious bursal disease virus and the protection conferred against them by a commercial vaccine strain of intermediate virulence were examined in specific-pathogen-free chickens. Based on clinical signs, mortality, and macroscopic lesions in susceptible chickens, the isolates designated as A-Delmarva and U-28 were distinct from a previously known serotype I virulent isolate (Edgar). Histopathological analysis of the bursa of Fabricius did not establish differences between the field isolates. Although the vaccine strain produced some degree of bursal damage in antibody-free chickens, it was significantly less severe than the damage caused by the field isolates. The active immune response induced by vaccination was cross-protective against the pathological effects produced by the different isolates used in this study. |
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