Atrophy of the primary lymphoid organs of meat pigeons in Italy associated with circoviruslike particles in the bursa of Fabricius.

During a survey effected in a meat pigeon slaughterhouse of central Italy, atrophy of primary lymphoid organs (bursa of Fabricius and thymus) and hypoplasia of bone marrow were observed. Histologic, ultrastructural, and hematologic examinations were performed on a total of 80 randomly selected 30-day-old meat pigeons. By histologic studies, lymphocytic depletion and necrosis with cyst formations in the bursa of Fabricius were detected in all subjects that showed thymus and bursa atrophy at necropsy. Basophilic intranuclear inclusions were also observed in bursal cells. After ultrastructural studies, these inclusions were proved to be viral particles resembling circoviruslike particles in morphology and size. Severe lymphocytic depletion of the bursa was plausibly associated with the presence of the viral particles.