Transmission of Erythroleukosis in Young Chickens

IN THE spring of 1935 a spontaneous outbreak of erythroleukosis occurred in two pens of young chickens at this ex-periment station. The disease occurred in pens 2 and 3 in a brooder house housing eight pens of Single Comb White Leghorn chickens ranging in age from 2 to 10 weeks. The construction of this house was such that the only means of entrance into these two pens was through the other pens. The disease did not appear in any of the other groups of chickens in this house. There were 108 chickens 39 days of age in pen 2 when the disease was first diag-nosed. Two days later the disease was diagnosed in pen 3, which contained 123 chickens 30 days of age. Diagnosis was based upon macroscopic lesions, blood-film, and histopathological examinations. During 14 days following the onset in pen 2, 32.4 percent of the chickens died or were destroyed. During 11 days following the onset in pen 3, 14.6 percent of the chickens died or were destroyed. Blood-films were made from each sick chicken before it was destroyed. These blood-films were stained by Wright's meth-od. The presence in the blood-films of varying numbers of erythroblasts and dis-torted erythrocytes or immature myelo-blastic cells was considered as diagnostic evidence of the disease. On autopsy en-largement of the liver was observed in all chickens. The spleen was enlarged in all but one and the kidneys enlarged in 21 out of S3. Table 1 gives the results of autopsies and examination of blood-films of the chickens which died or were de-stroyed during the 14 and 11 days respec-tively following the outbreak in pens 2 and 3. Histopathological sections made from TABLE 1.—Results of autopsies and examination of blood-films in a spontaneous outbreak of erythroleukosis in young chickens Blood pictur