Abstract
Lymphoma is the most common neoplasm diagnosed in domestic cats.1 Further, lymphoma is becoming increasingly more common in exotic felids. Approximately 70% of domestic cats with malignant lymphoma are feline leukemia virus (FELV) positive, but the rate of positives varies with the anatomic form of lymphoma.3 In contrast, FELV is rarely detected in malignant lymphomas in exotic feline species. Treatments for lymphoma have been attempted in domestic cats and in general their lymphomas respond poorly to chemotherapies and have shorter remissions than other domestic animals.1,2 Treatments for lymphoma in exotic felids are 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. This study explores 27 cases of lymphoma in exotic felids collected through zoological institutions and those published in the literature. Factors such as species, sex, age at diagnosis, methods of diagnosis, lymphoma treatment(s), and period of survival after diagnosis were compared. Species diagnosed with lymphoma included 12 (44.4%) African lions (Panthera leo), 5 (18.5%) tigers (3 Amur tigers [Panthera tigris altaica], a bengal tiger [Panthera tigris tigris], and a white tiger [Panthera tigris]), 2 (7.4%) cheetahs (Acinonyx jubatus),4 2 (7.4%) mountain lions (Felis concolor), and one case each in a bobcat (Felis rufus), a clouded leopard (Neofelis nebulosa), a leopard (Panthera pardus), a pampas cat (Felis colocolo), a Siberian lynx (Felis lynx), and a snow leopard (Uncia uncia). Methods of diagnosis ranged from physical examination, ultrasound, radiographs, complete blood count (CBC), biopsies, fine needle aspirates, ocular examinations, and necropsy. The diagnosis of malignant lymphoma was confirmed in all cases by microscopic evaluation. Treatments consisted of no treatment, supportive care treatments, splenectomy, ovariohysterectomy and enterotomy, and various chemotherapies. Survival after diagnosis ranged from zero days to 7 mo. One case, an African lion, was treated by a splenectomy, followed by chemotherapy with doxorubicin HCl (doxorubicin hydrochloride injection, USP, Ben Venue Labs, Bedford, OH, USA; 30 mg/m2 IV once), prednisone (Roxane Laboratories, Inc., Columbus, OH, USA; 0.55 mg/kg PO every other day), and lomustine (CCNU®, Bristol-Myers Squibb Co., Princeton, NJ, USA; 60 mg/m2 PO every 21 days for four treatments, then every 6 wk). Complete clinical remission was confirmed 2 mo after treatment was initiated through bone marrow biopsy results and a CBC. Treatment is ongoing and no clinical relapse has been noted since February 2004.
Acknowledgments
The authors would like to thank the following institutions or organizations for their participation in this study: Audubon Zoo, Binder Park Zoo, Buffalo Zoo, Cincinnati Zoo and Botanical Garden, Granby Zoo, Hogle Zoo, Indianapolis Zoo, Knoxville Zoo, Minnesota Zoo, National Zoo, Philadelphia Zoo, Potter Park Zoo, San Francisco Zoo, Toledo Zoo, Toronto Zoo, Tulsa Zoo, Wildlife Way Station, and Woodland Park Zoo.
The authors would also like to thank: Potter Park Zoo’s animal keepers, Gerry Brady, Dennis Laidler, and the rest of the zoo and society staff and volunteers; Ramona Kwapisyewski, CVT Surgeons of Mid-Michigan, James Ford and crew; MSU CVM: George Bohart, Lori Bidwell, Heather Flaherty, Diana Rosenstein, Bryden Stanley, Brian Teunissen, Jennifer Thomas, Cheryl Swenson, Vanessa Rengstorf, and all of the MSU CVM students who helped.
Literature Cited
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4. 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.