Abstract
Necropsy of 2 racing pigeons that had suffered from sluggishness, loss of appetite, and diarrhea revealed severe peritonitis. Microscopic examination showed atrophy of the lymphoid follicles with severe depletion of lymphocytes and reticular-cell replacement in the bursa of Fabricius. Abundant botryoid basophilic intracytoplasmic inclusion bodies were found in reticular cells and in macrophages in the bursal follicle. In addition, chlamydial intracytoplasmic inclusion bodies were found in macrophages infiltrating the polyserositic lesions. Electronmicroscopical examination of basophilic inclusion bodies in the bursa of Fabricius revealed numerous virus particles resembling circovirus. They were about 15 nm in diameter and demonstrated a paracrystalline arrangement. Our findings confirm these cases as concomitant infection with a circovirus and with Chlamydia psittaci, suggesting the existence of a pigeon circovirus in Japan.
