Unusual pathology of canary poxvirus infection associated with high mortality in young and adult breeder canaries (Serinus canaria)

Mortality in excess of 65% occurred in a flock of 450 canaries (Serinus canaria). Clinical signs in the canaries included severe respiratory distress, loss of feathers and/or scaly skin on the head, neck and back, anorexia, loss of weight and fluffed-up appearance of several days duration before death. Gross pathology in most of the canaries included thickened eye lids and small scab-like nodules on the skin of the head and neck, enlarged thymus, mild to severe consolidation of lungs and exudate in the sinuses and trachea. A few birds also had thickened air sacs and enlarged and pale spleens. Microscopically unusual lesions included severe epithelial proliferation and hypertrophy and mononuclear inflammatory cells containing eosinophilic intracytoplasmic inclusion bodies of poxvirus in the thymus, bursa of Fabricius, spleen, bone marrow, air sac, peritoneum, external and middle ears, and lachrymal gland. Similar inclusion bodies associated with inflammation were also seen in the epidermis, dermis, feather follicles, conjunctivae, sinuses, turbinates, choana, oral mucosa including tongue, oesophagus, larynx, trachea, syrinx and bronchi and parabronchi of lungs. Some of the birds also had concurrent bacterial, mycotic and polyomavirus infections. Poxvirus was isolated from lungs and skin in chicken embryo liver cells and confirmed as avian poxvirus by polymerase chain reaction.