Abstract
African hunting dogs (Lycaon pictus) are critically endangered African canids that are actively managed by an SSP in zoos. A review of cases in two pathology databases, Northwest ZooPath and Michigan State University, identified 45 individual wild dogs in their archives. Of these, 20 individuals had tumors of the skin. These skin tumors included apocrine hyperplasia, adenomas, and adenocarcinomas; mammary adenomas and adenocarcinomas; mast cell tumors; a hemangioma; and a lipoma.
The apocrine tumors were most common (14 of 20 animals) and ranged from areas of glandular hyperplasia to adenocarcinoma. An additional three cases were also reported previously by two of the authors.1 As seen in these dogs, the behavior and morphology of these tumors are unusual, in that they are typically multiple and found along the dorsal midline, often between the scapulae. These tumors are usually well-demarcated and multi-lobular arranged on a thin fibrovascular network. Distinct ducts were variably present. Individual cells are discrete polygonal with abundant eosinophilic granular cytoplasm, though vacuolation of the cytoplasm is often present suggesting some degree of sebaceous differentiation. Malignancy in these tumors is usually demonstrated by local invasion. In one case, apocrine gland adenocarcinoma was the likely cause of death. A gender predilection for females and possibly a history of contraception are being investigated. Further characterization of these tumors by immunohistochemistry is also pending.
Mammary neoplasia was also observed in 5 of 20 animals. These tumors included adenomas and adenocarcinomas, leading to death in at least one individual. In some cases, these tumors coexisted with apocrine tumors of the dorsal midline. Mast cell tumors were present in 2 of 20 animals with skin tumors. One hemangioma and one lipoma were also reported.
In contrast to this review, a retrospective study of wild dog disease and mortality in captivity in South Africa demonstrated no skin tumors from 87 animals.3 A similar review of morbidity and mortality in a wild population examined 46 animals, and though 85% of the dogs had skin disease, none had neoplasia.2
Literature Cited
1. Trupkiewicz, J. and A. Newton. 2003. Case # 33956. Proceedings of the 2003 C. L. Davis Zoo and Wildlife Pathology Workshop.
2. van Heerden J., M.G. Mills, M.J. Van Vuuren, P.J. Kelly, M.J. Dreyer. 1995. An investigation into the health status and diseases of wild dogs (Lycaon pictus) in the Kruger National Park. J. S. Afr. Vet. Assoc. 66:18–27.
3. van Heerden J., R. Verster, M.L. Penrith, I. Espie. 1996. Disease and mortality in captive wild dogs (Lycaon pictus). J. S. Afr. Vet. Assoc. 67:141–5.