Pathology of lymphosarcoma in sheep induced with bovine leukemia virus.

Sixty-nine sheep were infected with bovine leukemia virus from bovine lymphosarcoma materials. Twenty-four developed lymphosarcoma and died from 13 to 66 (average, 29) months later. Circulating lymphocytes were increased to leukemia levels (70,000 to 403,000/cu mm blood) in only eight sheep within 2 to 3 months of death. Various lymph nodes and visceral organs including heart, abomasum, uterus, kidneys, and urinary tract were commonly affected as in cattle with the adult form of lymphosarcoma. In one sheep the skin was involved. The liver was involved in only one case. This was in contrast to more frequent involvement reported in literature for naturally occurring lymphosarcoma. The neoplasms in experimental sheep are regarded as a mixture of reticulum or histiocytic cells and lymphoid cells with transitional forms supported by a usually sparse and diffuse fibroplasia and a web of silver-staining reticulin fibers.