Question

Why are nodules present in visceral organs in lymphoid leucosis?

Answer 1

Members of this RNA group of viruses have similar physical and molecular characteristics and share a common group-specific antigen. Detection of the major antigen (p27) present in the core of leukosis/sarcoma viruses forms the basis of several diagnostic tests. Lymphoid leukosis occurs naturally only in chickens. Experimentally, some of the viruses of the leukosis/sarcoma group can infect and produce tumors in other species of birds or even mammals. The infection is known to exist in virtually all chicken flocks except for some SPF flocks from which it has been eradicated. Tumor mortality commonly accounts for ~1%–2% of birds, with occasional losses of ≥20%. Subclinical infection, to which most flocks are subject, decreases several important performance traits, including egg production and quality. The frequency of infection has been reduced substantially in the primary breeding stocks of several commercial poultry breeding companies, particularly egg-type breeders. In recent years this control program has expanded, and infection has become infrequent or absent in certain commercial flocks. The frequency of lymphoid leukosis tumors even in heavily infected flocks is typically low (<4%), and disease is often inapparent. As much as 1.5% excess mortality per wk has been reported in commercial broiler-breeder flocks naturally infected with subgroup J avian leukosis virus.