Disseminated avian mycobacteriosis in a free-living grey heron (Ardea cinerea).

Wild birds share with humans the capacity for moving fast over large distances. During migratory movements, birds carry pathogens that can be transmitted between species. One of these concerning pathogens is Mycobacterium spp. A necropsy was performed in a grey heron (Ardea cinerea) that had been medically treated for a polyarthritic process. Grossly, firm white-yellowish nodules of various size, resembling granulomas, were observed in right carpal joint, both patellar joints, neck musculature, palate, pharynx, larynx, nasal sinuses, pericardial sac, air sacs, proventriculus and intestinal serosa, pancreas, kidneys, adrenal glands, and oviduct. Microscopically, these lesions were composed of multinucleated giant cells, large macrophages, and lymphocytes, with a central zone of necrosis and in some cases with peripheral fibrosis. Acid-fast bacilli were detected within these lesions. Lesions were cultured and Mycobacterium avium subsp. avium was identified. To the best of our knowledge this is the first description of mycobacteriosis in grey herons. Although the grey heron is currently considered a least-concern species, avian mycobacteriosis remains a threat on the conservation management of endangered avian species, and constitutes a public health concern as well.