Abstract. An epornitic of canary pox occurred in white-crowned sparrows (Zonotrichia leucophrys gambelli) , golden-crowned sparrows (Zonotrichia atricapilla) , and house sparrows (Passer domesticus), which had been caught in the wild and were being studied in laboratories. Of 900 exposed birds, 100 died naturally with the disease and 200 with clinical signs, and their 600 cage mates were killed. The earliest lesion was proliferative dermatitis around the eyes and beak. Next, severe ulcerative dermatitis, often with secondary bacterial and mycotic infections, developed under the wing; rhinitis, pneumonia, pleuritis, and peritonitis occurred in advanced cases. Histologically, there were eosinophilic, sudanophilic, cytoplasmic inclusions in epithelial cells and in subepidermal lymphoreticular cells. The isolated virus produced 100% mortality when inoculated into white-crowned sparrows, house sparrows, and canaries but only local cutaneous reactions in pigeons, turkeys, and chickens.Wild passerine birds are increasingly used in biomedical research. Among the potential diseases in such species, canary pox is probably the most serious threat, since it is highly infectious [3, 271, produces almost 100% mortality in affected birds [3,7, 231, and may occur in a latent form with the virus being shed from lesions for up to 13 months [18]. It may thus be introduced from the wild into stocks of laboratory-maintained birds, with devastating results.The canary poxvirus is one of the four major subgroups of the avian poxviruses ; the other three are fowl poxvirus, pigeon poxvirus, and turkey poxvirus [3,5,8, 13, 351. These three viruses usually cause a cutaneous disease of high morbidity but variable mortality [8]. Large pocks with umbilicated centers form on the skin. Within the cutaneous lesions, which are generally confined to the epidermis, there are pronounced hypertrophy and hyperplasia of epithelial cells. The cytoplasm of these cells often contains Bollinger bodies, that is, large eosinophilic inclusions composed of clusters of viral particles [8,24].
