Abstract
It is well known that macropods utilize the tail as an aid in balancing.1,2 The evolution of pentapedal gait allows the kangaroo to move more economically than similar sized running bipeds or quadrupeds.1 These facts cause obvious concerns when considering the ramifications of tail amputation.
A 5-year-old intact female red kangaroo (Macropus rufus) was presented with an abnormal positioning of the tail and weight loss of several days duration. Physical examination revealed cellulitis and devitalization of the distal ½ of the tail. Radiographs revealed osteomyelitis of several coccygeal vertebrae. Amputation of an estimated 85% of the tail was performed under general anesthesia. The animal recovered uneventfully and adapted well to the loss of the tail.
Case Report
A 5-year-old intact female red kangaroo (Macropus rufus), weighing 17 kg, was presented with an abnormal positioning of the tail and weight loss of several days duration. The animal was housed with 28 additional conspecifics of various ages and genders in a five-acre naturalistic exhibit during the day. During the evening, the animals were housed in an outdoor gravel and sand yard measuring 25×20 m, with access to indoor wooden stalls with cement floors. The kangaroos were maintained on a pelleted alfalfa-based diet (Mazuri ADF, Purina Mills, Inc., St. Louis, MO, USA), with alfalfa hay and a variety of natural enrichment “treats” consisting of whole wheat bread, bamboo, vegetables, and fruits.
The animal was immobilized with 275 mg ketamine hydrochloride (Ketaset, Fort Dodge Laboratories, Fort Dodge, IA, USA) and 75 mg xylazine hydrochloride (Rompun, Bayer Corp., Shawnee Mission, KS, USA), and maintained on 2.5% isoflurane (AErrane, Ohmeda Pharmaceutical Products Division, Inc., Liberty Corner, NJ, USA) via facemask. Intravenous buffered lactated fluids (LRS, Abbott Laboratories, Chicago, IL, USA) were administered at 20 ml/kg/h. Physical examination revealed devitalized “dry gangrene” tissue of the distal half of the tail with a 8×5 cm necrotic area over the ventral aspects of coccygeal or caudal (Cd) vertebrae 9–11. Survey radiographs revealed osteomyelitis of Cd 5–6 and Cd 11–12. Blood for a complete blood count (CBC) and selected serum chemistries were unremarkable.
The combination of weight loss, necrosis, devitalization, and ascending osteomyelitis precluded medical therapy, and the tail was amputated. Standard technique for tail amputation as for dogs was performed.3 After sterile preparation, the skin was incised in a double, dorsoventral “V” over Cd 3–4, with the dorsal aspect extending beyond the ventral aspect. The median caudal artery and the paired lateral caudal arteries and veins were identified and ligated with 3–0 polyglactin (Vicryl, Ethicon, Inc., Somerville, NJ, USA). Blunt dissection of the sacrocaudal musculature continued to the coccygeal vertebrae. The coccygeal vertebrae and tail were removed after separation of Cd 3 and 4. Approximately 80 cm of the tail was removed. The remaining tissue was irrigated with 100 mg of gentamicin sulfate (Gentocin, Schering-Plough Animal Health Corp., Omaha, NE, USA) in 10 ml of a 0.9% saline solution (0.9% NaCl, Abbott Laboratories, Chicago, IL, USA). Fascia muscle sheaths were sutured together in a linear pattern with 2–0 polyglactin simple interrupted sutures. The skin was closed with 1–0 nylon non-absorbable sutures (Ethilon, Ethicon, Inc., Somerville, NJ, USA) in a simple interrupted pattern.
The remaining 8–10 cm of tail was bandaged and changed every 6–9 days during immobilization with 2 mg/kg tiletamine/zolazepam (Telazol, Fort Dodge Laboratories, Fort Dodge, IA, USA). A total of six bandage changes were performed. Aerobic cultures revealed scant growth of beta-hemolytic Streptococcus, heavy growth of Klebsiella pneumoniae, and heavy growth of Enterococcus faecalis. Anaerobic cultures were negative. Based upon aerobic sensitivities, antibiotic therapy was initiated with 28 mg/kg sulfadimethoxine/trimethoprim (Tribrissen 48%, Mortar and Pestle Pharmaceuticals, Des Moines, IA, USA) intramuscularly once daily for 14 days. Sutures were removed 5 weeks after the initial surgery.
Only minor difficulty was noted when the animal started to recover, but adaptation to the tail loss was rapid. The tail “stub” does not touch the ground, yet the animal is able to stand erect when startled. When walking, the kangaroo places noticeably more direct weight upon the tarsal joints. This may predispose to future arthritic problems but has not been noted to date. The muscles of the hind limb have hypertrophied, especially what appear to be the gluteal and thoracolumbar muscles, and the animal has minimal balancing problems. On very rare occasions, the kangaroo cannot right itself from a laterally recumbent position. In these instances, keepers have assisted in righting the animal.
Tail amputation in this kangaroo was considered a complete success, and would be contemplated in any severely traumatized, neoplastic, or infectious process involving the tail of macropods housed at the Kansas City Zoological Gardens.
Acknowledgments
The author greatly appreciates the efforts of the animal health and zookeeper staff for postoperative care of this kangaroo.
Literature Cited
1. Dawson, T.J. 1983. Monotremes and Marsupials. Edward Arnold (Publishers) Limited, Bedford Square, London, 67–69.
2. Domico, T. 1993. Kangaroos: The Marvelous Mob. Mandarin Offset, Hong Kong, China. 23.
3. Slatter, D. 1993. Small Animal Surgery. WB Saunders, Philadelphia, Pennsylvania. 344.