The control of lymphoid leukosis in a flock White Plymouth Rock chickens

Abstract
Lymphoid leukosis (LL) was successfully controlled in a commercial basic breeding line of White Plymouth Rock chickens. The control method has been developed for breeder flocks and consists of three elements: The vaccination raises a solid immunity to horizontal LL virus exposure and, due to the age‐related resistance, tumour formation does not follow. No excretion of LL viruses could be detected in three generations of White Plymouth Rock chickens to which the three elements of the control procedure were applied. Clinical disease was not observed in any of the chickens under notice.