abstract

In February of 2007, Snow, a 12-year-old intact female polar bear, was anesthetized for routine physical exam. She had a five year history of a seasonal pruritic dermatopathy, beginning in early fall and extending through to the following spring. Clinical signs ranged from mild alopecia and erythema to severe excoriation over the head, neck, axilla, and interscapular regions. Multiple endocrine tests, skin scrapings, cultures and biopsies yielded little information of diagnostic or therapeutic value. Psychogenic factors were considered and addressed both environmentally and medically. A hypoallergenic food trial was also attempted without success.

Blood collected during this examination was submitted for routine CBC and chemistries, and results were found to be within normal limits. An additional sample was sent to a commercial diagnostic laboratory for specific allergen sensitivity testing (Allercept®, Heska Veterinary Diagnostic Laboratories, Loveland, CO). Skin biopsies taken at that time were submitted for histopathology, and interpreted as mild diffuse hyperkeratosis with crusting. Fungal cultures were negative at four weeks.

Results from the allergen testing were surprising. Two separate sets of allergens specific to individual geographical regions of the country were assayed, as well as a food protein panel. Overall, this bear reacted very strongly to environmental factors such as house dust mites, as well as a variety of grass and weed pollens. Of the food allergens, milk was the only one to elicit what would be considered a positive result in companion animals. For controls, these tests were also performed on the other three conspecifics held at Sea World Orlando, and only her male sibling exhibited any significant levels, yet not to the magnitude of Snow.

High dose corticosteroid therapy was instituted (prednisone 280 mg. P.O. BID) in addition to an antihistamine (hydroxyzine 500 mg. P.O. TID). She was on concurrent glucosamine therapy for osteoarthritis resulting from metabolic bone disease as a young cub prior to coming to Sea World. The exhibit and holding areas were thoroughly cleaned and new filters installed in the air handling system. Whereas straw was occasionally placed in her enclosure for bedding, this practice was immediately eliminated.

Although treatment was started during a period when the bear would normally have begun to show mild seasonal clinical improvement, response to this new pointed therapy was dramatically augmented. Within a few weeks, her pruritus was greatly reduced, and her fur began to gradually regrow. By four weeks post initiation of treatment, her coat condition had improved to a point previously unseen by any caretakers since her dermatopathy had first been noted.

Since that time, in an attempt to avoid the potential side effects of long term corticosteroid therapy, a subsequent 30 day trial of cyclosporine has been tried without positive response.

Briefly stated, the technology utilized in this case is an ELISA test which detects and quantitates allergen specific IgE, the immunoglobulin usually found in elevated levels in the blood of allergic animals. This particular test can detect as little as 0.3 nanograms of allergen specific IgE, even while in the presence of one million times normal circulating levels of nonspecific IgE.² Additionally, this type of testing can facilitate hyposensitization/desensitization therapy in the patient, despite its obvious challenges in administration to polar bears.

While there has been one previous case report of atopic dermatitis in polar bears,¹ this is believed to be the first account of the use of this testing modality in this species, and may prove to be of some benefit to zoological institutions in diagnosing bears with seasonal pruritic skin conditions, as well as subsequent therapeutic options, including immunotherapy.

acknowledgements

Many thanks to the Animal Care Department of Sea World Orlando for their assistance in the management and photo documentation of this case.

References

1.  Harper J, White S, Stewart L, Pelto J. 1988. Proceedings of the American Association of Zoo Veterinarians. 97-98.

2.  Technical Press Release on behalf of Heska Veterinary Diagnostic Laboratories, Loveland, CO, 2001.