Pathogenicity of recent isolates of infectious bursal disease virus in specific-pathogen-free chickens: protection conferred by an intermediate vaccine strain.
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.
Rosales
A G
AG
Department of Avian Medicine, College of Veterinary Medicine, University of Georgia, Athens 30602.
Villegas
P
P
Lukert
P D
PD
Fletcher
O J
OJ
Mohamed
M A
MA
Brown
J
J
D000818:Animals; D002645:Chickens / Q000276:immunology*; D007243:Infectious bursal disease virus / Q000276:immunology / Q000302:isolation & purification / Q000472:pathogenicity*; D012087:Reoviridae / Q000472:pathogenicity*; D013047:Specific Pathogen-Free Organisms; D014611:Vaccination / Q000662:veterinary; D014765:Viral Vaccines / Q000276:immunology*; D014774:Virulence
D014765:Viral Vaccines