Abstract
Lymphomas are common in exotic felids especially in African lions (Panthera leo).1-3 This study evaluates age at diagnosis, sex, clinical signs, lymphoma immunophenotype, treatment(s), and length of survival time from diagnosis. A total of 11 lions were included in this study. The average age at time of diagnosis was 16.5 years, 82% were male. Clinical signs included weight loss, lethargy, seizures, epistaxis, vomiting, collapse, or sudden death. The spleen was significantly enlarged in all but one case. Bone marrow involvement was only detected in one lion, but metastatic spread to peripheral lymph nodes and liver was common. All lymphomas were confirmed microscopically. Eight cases were confirmed to be T-cell lymphomas, and one case was confirmed to be a B-cell lymphoma. Therapies consisted of no treatment, supportive care, splenectomy, and various chemotherapies. Survival after diagnosis ranged from 0 days (euthanasia) to 240 days, with a majority of the animals being dead within 30 days after the diagnosis. One African lion with a small cell T-cell lymphocytic lymphoma was treated by a splenectomy, followed by chemotherapy with Adriamycin (Doxorubicin Hydrochloride Injection, USP, Pharmacia, Inc., Kalamazoo, MI, USA), prednisone (Roxane Laboratories, Inc., Columbus, OH, USA), and lomustine (CCNU®, Bristol-Myers Squibb Co., Princeton, NJ, USA). Complete clinical remission was confirmed by bone marrow biopsy and CBC 2 months after treatment was initiated. Treatment is ongoing and no clinical relapse has been noted for over 16 months. Treatment for lymphoma in exotic felids is uncommon, usually attributed to the challenge of handling the animals, and to typically late diagnosis. Recently, however, chemotherapeutic regimens have been attempted. The actual response to the chemotherapeutic protocols is still largely unknown due to a limited sample size. The long-term survival in the one animal presented here may be due to the fact that it has a small T-cell lymphocytic lymphoma (T-zone lymphoma) which has an indolent biologic behavior.
Acknowledgments
The authors would like to thank the following institutions or organizations for their participation in this study: Hogle Zoo, Knoxville Zoo, Potter Park Zoo, San Francisco Zoo, Toronto Zoo, Wildlife Way Station, and Woodland Park Zoo.
Literature Cited
1. Douglass, E.M. 1979. Lymphosarcoma and blockage of the biliary duct in an African lion (Panthera leo). Vet Med Sm Anim Clin. 74:1637–1641.
2. Marker, L., L. Munson, P.A. Basson, and S. Quackenbush. 2003. Multicentric T-cell lymphoma associated with feline leukemia virus infection in a captive Namibian cheetah (Acinonyx jubatus). J Wildl Dis. 39:690–695.
3. Poli, A., F. Abramo, P. Cavicchio, P. Bandecchi, E. Ghelardi, and M. Pistello. 1995. Lentivirus infection in an African lion—a clinical, pathological and virological study. J Wildl Dis. 31:70–74.