lymphoid leukosis

noun

: a neoplastic disease of chickens that is caused by a retrovirus (species Avian leukosis virus of the genus Alpharetrovirus) and is characterized by the formation of nodular or diffuse lymphoid tumors composed mostly of B cells and occurring especially in the bursa of Fabricius, liver, and spleen and sometimes in the kidneys and gonads

Chickens with lymphoid leukosis show nonspecific clinical signs including inappetence, weakness, diarrhea, dehydration, and emaciation.

—The Merck Veterinary Manual, 9th edition

see avian leukosis