Mycobacterium intracellulare (MIT) was diagnosed postmortem by culture and histopathology in seven birds from a flock of little blue penguins (Eudyptula minor) at the Henry Doorly Zoo (HDZ) representing 20% of the population deaths. Clinical signs in affected birds included respiratory distress with chronic debilitation. On exam, plaques were noted in the larynx, trachea, and soft tissue of the caudal oropharynx.
A treatment protocol of rifampin (Sandoz Inc., Princeton, New Jersey, USA; 15 mg/kg PO SID), ethambutol (Pantheon Inc., Toronto, Ontario, Canada; 15 mg/kg PO SID) and clarithromycin (Abbott Laboratories, North Chicago, Illinois, USA; 10 mg/kg PO SID) was initiated in 2004. Gastric washes, fecal samples and throat plaques were obtained antemortem on five birds and tested by culture and polymerase chain reaction (PCR). MIT was detected on gastric wash and throat plaque PCR. Antimicrobial susceptibilities indicated the organism was sensitive to the regimen. Three more birds died during treatment. After the seventh bird died, a susceptibility performed in 2007 indicated the MIT was resistant to most antibiotics tested including rifampin and ethambutol. One more death occurred. Treatment was changed to minocycline (Ranbaxy Pharmaceuticals Inc., Jacksonville, Florida, USA; 10 mg/kg PO BID) and clarithromycin (10 mg/kg PO SID).
Clinical signs and visualization of plaques have not recently been noted. The proposed mechanism of transmission is exposure to wild birds but the etiology has not been determined. Avian mycobacteriosis caused by MIT has not previously been reported in this species.
The authors would like to thank the laboratory staff at the University of Nebraska Medical Center and the veterinary technicians and the aquarium bird keeper staff at Omaha’s Henry Doorly Zoo for their participation and support in this case study.