Isolation of Avipoxvirus from Tongue of Canaries (Serinus canaria) Show Severe Localized Proliferative Glossitis

摘要

Poxvirus was the causative agent of two unusual outbreaks of proliferative glossitis in canary (Serinus canaria forma domestica) breeders in the Northern Italy. A total of 45, 7-9-mo-old canaries were submitted in fair postmortem conditions to the Istituto Zooprofilattico Sperimentale delle Venezie at the beginning of November 2005 for diagnostic investigation. Birds belonged to two unrelated and geographically distant aviaries in northern Italy, herein identified as Aviary A and Aviary B. The two breeder flocks had both attended the same bird exposition held at the beginning of October and started experiencing an onset of high mortality 3 wk after the show. Twelve red factor-melanin canaries from Aviary A (Mantua) and 33 dominant white and recessive white canaries from Aviary B (Vicenza) were submitted for laboratory investigations. Clinical signs were unspecific and consisted of depression, ruffling of the feathers, epistaxis, and anorexia due to decreased feed and water intake. Postmortem findings revealed a severe increase in volume, thickening, and hardening of the tongue, which had turned pinkish to dark brown. No apparent gross lesions were noticed in integumentary, respiratory, and digestive systems or other internal organs. Histopathologic evaluation of the tongue revealed severe proliferation of the stratified squamous epithelium containing numerous large eosinophilic intracytoplasmic inclusion bodies (Bollinger bodies) displacing the nuclei of the cells peripherally. Severe ulceration of the surface epithelium, fibrinoheterophilic plaque formation, and moderate basal lymphoplasmacytic infiltrations were also associated with the proliferative lesion. Poxvirus was successfully isolated from the lesions in tissue cultures but not in specific-pathogen-free chicken embryonated eggs. Typical large, brick-shaped viral particles of 300-450 nm were also observed in affected tongues by transmission electron microscopy. This is the first report of multiple outbreaks of "poxvirus glossitis'' in canaries.