Abstract

Malignant melanoma is a relatively common penguin neoplasia, with a reported prevalence of 2%.¹ These aggressive neoplasms typically occur on the non-feathered skin of the foot or hock, subcutaneous muscle, and the skin of the inguinal region.¹ Immunotherapy has been used in non-domestic mammals with some success.² The canine melanoma vaccine (Oncept®, Merial) targets the protein tyrosinase, which is normally expressed in melanocytes. Tyrosinase is conserved across species and is present in birds.³ Oncept® is a xenogeneic DNA vaccine encoding human tyrosinase, which elicits an antigen-specific immune response in the host directed against melanoma cells. The case presented here describes the diagnosis and treatment of malignant melanoma in a 25-year-old male African penguin, who presented with a raised pigmented mass within the right nare. An excisional biopsy was performed to confirm the diagnosis of a malignant melanoma and a therapeutic plan was initiated including meloxicam, radiation, and immunotherapy. The penguin was vaccinated with the canine melanoma vaccine, Oncept®, which was given intra-dermally every other week for 4 doses and boostered at 6 months, with no adverse effects. Tyrosinase antibody serum levels were measured using an anti-human tyrosinase specific enzyme-linked immunosorbent assay. Increasing human tyrosinase-specific antibody levels were documented in this penguin over the course of the vaccination protocol, indicating a positive humoral immune response to the Oncept® vaccination. The penguin died 15 months after initial diagnosis from an unrelated cause and no evidence of metastasis was identified on necropsy, supporting a positive clinical response of the vaccine.

Acknowledgements

The authors would like to thank the penguin husbandry team at Mystic Aquarium and the radiation oncology team at the Cumming's School of Veterinary Medicine at Tufts University for their assistance with this case.

* Presenting author

Literature Cited

1.  Duncan AE, Smedley R, Anthony S, Garner MM. 2014. Malignant melanoma in the penguin: characterization of the clinical, histological, and immunohistochemical features of malignant melanoma in 10 individuals from three species of penguin. J Zoo Wildl Med. 45:534–549.

2.  Steeil J, Schumacher J, Ramsay EC, Lembcke L, Lee ND. 2013. Application and limitation of advanced diagnostic and therapeutic modalities in zoologic species with malignant melanoma. AAZV Proceedings, Salt Lake City, UT; 71–72.

3.  Austin LM, Boissy RE. 1995. Mammalian tyrosinase-related protein-1 is recognized by autoantibodies from vitiliginous Smyth chickens. An avian model for human vitiligo. Am J Pathol. 146:1529–1541.