Submitted to: American Veterinary Medical Association Abstract
Publication Type: Abstract Only
Publication Acceptance Date: July 16, 2005
Publication Date: July 16, 2005
Citation: Davis, C.A., Mays, J.K., Pandiri, A., Fadly, A.M. 2005. Comparative evaluation of the pathogenicity of an extraneous subgroup A avian leukosis virus isolated from commercial Marek's disease vaccines [abstract]. American Veterinary Medical Association. p. 58. Technical Abstract: The pathogenicity of an extraneous subgroup A avian leukosis virus (ALV-A), isolated from commercial Marek's disease vaccines (Fadly et. al., Proc. USAHA; 2003; p.524-525) and termed B-39, was compared with that of Rous-associated virus-1 (RAV-1), the prototype strain of ALV-A. Chickens from ADOL lines 15I5 X 71 and 0 were used; each chicken from each line was intra-abdominally inoculated with approximately 10,000 infectious units of RAV-1 or B-39 virus at 7th day of embryonation. At hatch, and at 4, 8, and 16 weeks of age, chickens were tested for viremia, antibody and cloacal shedding; chickens were also observed for ALV-induced tumors within 16 weeks of age. In addition, at 8 and 16 weeks of age, bursa of Fabricius from three chickens per treatment group was microscopically examined for early lesions of ALV-induced transformation. Viremia and cloacal shedding results suggest that chickens from both lines were equally susceptible to infection with either virus. Within 16 weeks of age, none of the chickens inoculated with B-39 virus developed tumors, compared with 62%-67% of the chickens inoculated with RAV-1. The data suggest that strain B-39 of ALV-A is either non-oncogenic or of a very low oncogenicity, compared with that of RAV-1, the prototype strain of ALV-A.