Seyed Ahmad Madani - Department of Avian Diseases, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran
Mohammad Reza Haddad-Marandi - Avian Diseases Research Center, School of Veterinary Medicine, Shiraz University, Shiraz, Iran
Fatemeh Arabkhazaeli - Department of Parasitology, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran

A dead canary from a mixed species zoological garden was presented for diagnostic necropsy. Cachexia with prominent atrophy of pectoral muscles, yellowish brown discoloration of the liver and kidney, dark brown to black intestinal contents and moderate proventricular dilatation with some degree of catarrhal gastritis were the significant macroscopic findings. Parenchymatous organs like the liver, the spleen, the lung and the kidneys were extremely affected by massive diffuse necrosis and heavy infiltration of mononuclear inflammatory cells, histopathologically. Many giant bacilli resembling Macrorrhabdus ornithogaster were seen microscopically in the wet smear of the isthmus mucosa. Ghost-like unstained bacilli were revealed in the Giemsa stained contact smears of the liver and spleen. No typical mycobacterial granulomatous lesion was found in different tissues, but in Ziehl-Neelsen stained thin layer histologic sections from the liver, spleen, lung and kidney, numerous acid fast organisms were diffusely distributed. The case was diagnosed an atypical avian tuberculosis with concurrent macrorhabdosis. Mycobacterium sp.are capable of giving rise to a progressive disease in humans, especially in immunocompromised individuals. Cases of avian tuberculosis might be overlooked for lack of pathognomonic lesions suggestive of mycobacteriosis.

Atypical tuberculosis, Canary, Macrorhabdosis, Megabacteriosis, Mycobacteriosis