Introduction

Osteoarthritis (OA) is a serious malady of numerous species kept in zoologic collections. Clinical and radiographic signs can be seen in middle-aged animals and certainly in geriatric patients. This condition is especially noted in primates and cats from the genus Panthera.⁶ Medical management of domestic species includes rest, analgesics, and even surgical management. Glycosaminoglycans and glucosamines have recently found a place in zoologic medicine and have their value.⁷ Analgesics include opioids and nonsteroidal anti-inflammatories (NSAIDs). Opioids have limitations and may even be contraindicated in felids. NSAIDs have limitations with metabolism as well in these animals but with careful monitoring may be effective.

While animals in zoologic collections serve several purposes, their educational value may be the most significant. As such, it is well to think of them as companion animals and manage them as such to maximize their health and welfare. One such aspect of this care is behavioral modification/enrichment including the training of animals to facilitate medical management. The combination of this type of management has led to the use of a novel therapeutic approach in osteoarthritis in large cats to a satisfactory conclusion.

Case Report 1

A female Bengal tiger (Accession No. 50386) was first diagnosed with osteoarthritis of both coxofemoral joints on physical exam in May 1998 at 10 years of age. Pertinent medical history included a chronic struvite cystitis that was eventually controlled with ammonium chloride and antibiotics as needed. In spring and early summer of 1999, the tiger was noted by the caretaking staff to have a decrease in activity, especially swimming, moving off and onto a bench, running, and stretching up trees on the display. By July, conditioning to allow voluntary blood draws from the lateral tail vein was a steady husbandry feature. Because this was in place, the decision was made to try etodolac as an analgesic for the hip osteoarthritis and suspected spinal arthritis seen in large felids. Etodolac was started at 5 mg/kg PO q 48 h for five doses (600 mg at an estimated weight of 120 kg based on the latest physical exam). At the end of this course the response was judged to be excellent by the staff. The tiger was then tapered off to 600 mg q 72 h, again with an overall improvement in activity and comfort level. When the dose was extended beyond this interval there was some notation that she would be stiff in the mornings and subjectively did not appear to be as comfortable as before. The 72-hour interval was reinstated and has been in place ever since. Serum chemistries from blood samples taken from the tail vein while awake prior to etodolac therapy (n=3) revealed the following means: BUN 34 mg/dl, Cr 2.3 mg/dl, albumin 3.7 g/dl, AST 21 IU/L. Samples taken after the start of therapy (n=5) revealed the following means: BUN 39.4 mg/dl, Cr 2.34, albumin 3.4 g/dl, AST 20.2 IU/L. No statistic comparisons were attempted because of the small sample sizes, but it appears that the etodolac has not affected these parameters. Subjectively, this tiger has responded extremely well by running onto the display, climbing trees, and especially by swimming.

Case Report 2

A second female Bengal tiger (Accession No. 50385) was diagnosed radiographically with coxofemoral osteoarthritis in 1998. Several courses of chondrotin sulfates and glycosaminoglycans were initiated but appeared to be ineffective at improving the tiger’s condition. In spring of 1999 she developed a left forelimb lameness and a slight right-rear leg lameness. A course of etodolac was instituted on this animal as above at the same dose and interval. Blood was collected in the same manner as well. The clinical response was not as dramatic as in the first tiger, so a physical exam was performed. Severe proliferative osteoarthritis of the left elbow was seen radiographically. Several large osteophytes were surgically removed in an attempt to alleviate the discomfort and to return to normal use. Because the proliferation was so vast, this was minimally effective. Etodolac was reinstituted after the surgery. This tiger is not as reliable for voluntary blood sampling as the previous case, so awake sampling is limited, but a single sample taken prior to the etodolac revealed a BUN 24 mg/dl, Cr 2.5 mg/dl, albumin 3.4 g/dl, AST 21 IU/L. Post-therapy values are essentially identical with the means (n=2) of BUN 27.5 mg/dl, Cr 2.65 mg/dl, albumin 3.6 g/dl, AST 30.5 IU/L. Subjectively, this animal does move better than before the etodolac and the hindlimb lameness is essentially resolved, but the forelimb lameness persists. This tiger has, however, become the most dominant one of the group of three females and will run and jump upon her bench readily.

Discussion

Osteoarthritis is a disease of captivity in large felids. In a study of museum specimens OA could not be documented in wild felids of the genus Panthera.⁶ Degenerative spinal disease is another musculoskeletal condition that affects this genus in captivity that may warrant analgesic use.⁴ Analgesics for management of OA in this genus ranges from aspirin to glycosaminoglycans and glucosamines.⁷ Etodolac has not been studied in cats and is not recommended for this species because of the toxic effects of other NSAIDs.² In one review, NSAIDs are not even listed as a therapeutic option for domestic cats with OA.³ Etodolac at approximately 5 mg/kg q 48 h and then tapering to effect has resulted in good clinical resolution in one tiger (case report 1), and a combination of surgery and etodolac has resulted in satisfactory results in the other (case report 2). Hepatotoxicity associated with NSAID use are typically hepatocellular in nature, and dogs on a short course of etodolac have seen transient hypoalbuminemia.¹ Monitoring of serum chemistries demonstrated no change in liver or renal function over a protracted course of therapy, and no clinical signs of side effects were observed in either cat. Neither cat had a gastroscopic exam to rule out gastric ulceration, but no gastrointestinal signs have been observed. Objective evaluation such as gait analysis is not practical in this situation. Subjective evaluation from clinical staff and caretakers are in consistent agreement that both cats are improved since the etodolac therapy has been instituted. This evaluation may be the best overall assessment of pain control.¹ While both cats have varying degrees of coxofemoral OA, the tiger in case report 2 also had severe changes in both elbows with one requiring surgical removal of free osteophytes. While her clinical improvement has improved, her overall quality of life she has not responded as well as the tiger in case report 1. Etodolac has been reported to not only arrest the progression of osteoarthritis but also if instituted early enough actually reverse its clinical effects, leaving only residual pathology (i.e., osteophytic changes).⁵ Early diagnosis through a progressive preventive medicine program along with operant conditioning will allow early interventions and appropriate followups to ensure the highest standard of care for captive wildlife.

Literature Cited

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