Mycobacterial osteomyelitis in captive marsupials

Area of Science:

• Veterinary Pathology
• Zoological Medicine
• Microbiology

Background:

• Mycobacterial infections can cause significant morbidity and mortality in captive wildlife.
• Osteomyelitis, an infection of the bone, poses diagnostic and therapeutic challenges, particularly in non-domesticated species.
• Early detection and accurate identification of causative agents are crucial for effective management of infectious diseases in zoological collections.

Observation:

• Three marsupials at the National Zoological Park presented with clinical signs suggestive of osteomyelitis.
• Affected species included a Matschiei's tree kangaroo (Dendrolagus matschiei), a Parma wallaby (Macropus parma), and a long-nosed rat kangaroo (Potorous tridactylus).
• Clinical and pathological findings ranged from disseminated granulomatosis to localized bone lesions with necrosis and exudate.

Findings:

• Acid-fast organisms were detected via fluorescent staining in bone marrow and granulomas of the wallaby and rat kangaroo, respectively, though cultures remained negative.
• Mycobacterium avium serotype 15 was successfully isolated from the ischium and liver of the affected Matschiei's tree kangaroo.
• The diagnostic utility of auramine-O-rhodamine staining was demonstrated, while culture limitations were also highlighted.

Implications:

• This case series underscores the importance of considering mycobacterial infections in marsupials with bone abnormalities.
• The identification of Mycobacterium avium serotype 15 provides valuable etiological data for wildlife disease surveillance.
• Improved diagnostic strategies, potentially combining advanced staining techniques with molecular methods, may be necessary for definitive diagnosis of mycobacterial osteomyelitis in wildlife.