The Oncogenic Spectrum of Two “Pure” Strains of Avian Leukosis

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Abstract
Under experimental conditions conducive to full expression of their pathogenic properties, two “pure” strains of avian leukosis were studied. Six experiments involving 3,178 chickens were performed. Cell-free preparations of erythroblastosis strain R (Beard) caused visceral lymphomatosis in a high percentage of birds that survived the erythroblastosis. Similar cell-free preparations of the myeloblastosis strain A (Beard) caused myeloblastosis, visceral lymphomatosis, renal adenocarcinomas, and osteopetrosis. All combinations except myeloblastosis-visceral lymphomatosis were observed. Infectious levels were found in the oral washings and extracts of droppings (fecal-urinary) from chickens that showed signs of leukosis after intravenous inoculation of plasma from chickens with leukosis strain R and from others with leukosis strain A. Virus was also found in similar collections from noninoculated chickens that showed no evidence of disease, and were reared in contact with others inoculated with strain R. The virus of leukosis strain R and strain A was transmitted by bird-to-bird contact; the former produced erythroblastosis and visceral lymphomatosis, and the latter, visceral lymphomatosis, osteopetrosis, and renal adenocarcinomas in noninoculated pen mates.