Abstract

Nocardia spp. are aerobic actinomycetes characterized by branching filamentous Gram positive rods. Pathogenic nocardioforms including N. asteroides complex (N. nova, N. farcinica, N. brasiliensis, N. transvalensis) and N. otitidiscaviarum are ubiquitous in soil and water. They can opportunistically infect cetaceans through dermal contamination of wounds or inhalation of airborne particles. Specific cases reported by Robeck and Dalton in belugas described variations in clinical presentation involving neonates and adults, from a well-circumscribed mass/abscess to pneumonia and disseminated granulomatous lesions.¹

We report 4 serial infections of Nocardia spp. in a 35 yr old female beluga (Delphinapterus leucas) over the course of 4 years. They were treated successfully with trimethoprim sulfadiazine (TMS) 1:2 formulation, although treatment side-effects were observed. A novel formulation of TMS 1:2 was chosen following experience with successful treatment of nocardiosis in a 39 yr female beluga from the same exhibit, in 2007.³ This current beluga's infections were characterized by large subcutaneous granulomas or abscesses found on the caudoventral aspect of the abdomen and a large macular lesion near the scapula. Wounds were managed with surgical drainage or aspiration of the wound contents and oral TMS 1:2 formulation (8–10 mg/kg once daily), supplemented with oral folic acid (0.05 mg/kg three times daily). Three out of four infections occurred during pregnancy with no adverse effects to the fetus. Systemic spread of infection was not detected by screening of blood and milk samples for Nocardia spp. with bacterial PCR (Univ. of Illinois).

Sulfonamide antimicrobials are known to elicit some hypersensitivity reactions such as: fever, cutaneous eruption, hepatitis and blood dyscrasias (thrombocytopenia, neutropenia).² Previous accounts of hypersensitivity reactions, such as thrombocytopenia, neutropenia, have been reported in killer whales and a beluga.^1,3,4 Other associated clinical signs of hypersensitivity in a canine study included keratoconjunctivitis sicca (KCS), hemolytic anemia, arthropathy, uveitis, skin and mucocutaneous lesions, proteinuria, pancreatitis, facial edema, pneumonitis, facial palsy and meningitis.⁵ The clinical signs observed in this beluga case included appetite loss, azotemia, mucocutaneous ulceration, thrombocytopenia and neutropenia. Treatment duration with TMS 1:2 ranged from 50–97 days. Hypersensitivity reactions with TMS 1:2 were duration and dose dependent. Treatment with folinic acid, steroids and antihistamines was used to aid clinical recovery from the hypersensitivity. Other signs of azotemia and mucocutaneous ulceration responded to supportive therapy. The Nocardia sp. identified in this beluga was found to be sensitive to minocycline, doxycycline, amikacin and cefuroxime and TMS. Other oral antibiotics were found to be inferior to TMS 1:2 for the treatment of subcutaneous nocardiosis in this beluga. Therefore, close monitoring of clinical signs and blood parameters is necessary when using TMS 1:2 to identify early signs of hypersensitivity reactions, however it remains the treatment of choice when treating Nocardia spp. in cetaceans.

Acknowledgements

The authors would like to thank the veterinary and Wild Arctic animal training staff at SeaWorld San Diego.

* Presenting author

Literature Cited

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