Mycobacterial conjunctival granuloma in a Scaly-sided merganser (Mergus squamatus)

摘要

A five-year-old, female scaly-sided merganser was presented with a chronic recurrent conjunctivitis of the left eye. Physical examination showed a caseous nodular lesion at the palpebral conjunctiva associated with excessive tearing. Necropsy revealed caseous necrotic debris at the left conjunctiva and infra-orbital sinus, but also multiple granuloma in several internal organs. Histological examination showed granulomatous splenitis, hepatitis, arteritis, fibrinonecrotic enteritis and conjunctivitis, and also amyloidosis of liver and spleen. Bacterial and molecular tests of a conjunctival swab in the live animal showed the presence of a multiresistant Escherichia coli strain and Chlamydia psittaci, respectively. These bacteria had only a secondary pathogenic role. No premortem cytological examination or Ziehl-Neelsen (ZN) staining of the histological section of the conjunctiva biopt or additional tests, such as blood test and radiographs, were performed. Finally, a Mycobacterium avium infection of the conjunctiva and internal organs was confirmed following necropsy by ZN staining and PCR analysis. Local and systemic antimicrobial treatments with fluoroquinolones, tetracyclines and aminoglycosides were unsuccessful.