Study on the Pathogenicity of Chinese Strains of Subgroup J Avian Leukosis Viruses

The pathogenicity of 4 Chinese strains of subgroup J avian leukosis viruses (ALV-J), SD9901, SD9902, YZ9901 and YZ9902,was studied. The results showed that only SD9902 among the 4 strains induced mortality from myeloid leukosis (ML). In the 12 meat-type chickens inoculated with SD9902 at 1-day-old, 9 died between 22 days and 38 days after inoculation. No death or ML was found in chickens inoculated with the other 3 strains during the period of 6 months. These results suggested the SD9902 strain of ALV-J was an acute transforming virus, but SD9901, YZ9901 and YZ9902 were non-transforming viruses. All 4 Chinese strains did not induce any tumors in egg-type SPF chickens during 7 months after hatching when viruses were injected into 11-day-old embryos.