Abstract

A 14-mo-old male neutered Virginia opossum (Didelphis virginiana) was presented in May 2008 with scabs and hair thinning around the right shoulder area. He was treated with a gentamycin/betamethasone topical spray (Butler Animal Health Supply LLC., Dublin, OH 43017 USA), and appeared to improve for about 1 mo; however, he presented again in July 2008 with similar scabs and hyperemia of the skin on the shoulder. Physical examination revealed the presence of fleas, prompting treatment with imidacloprid (Advantage 10, Bayer Animal Health, Bayer Healthcare LLC, Shawnee Mission, KS 66201 USA). He was rechecked 3 wk later and found to be free of fleas. However, the scabs and skin hyperemia were still present. Allergy or contact dermatitis was suspected at this stage, and it was suggested that the cedar mulch, which was used for bedding, be removed.

One week later, treatment with prednisone (Butler Animal Health Supply LLC., Dublin, OH 43017 USA; 1 mg/kg p.o. s.i.d. for 7 days) was initiated, as removal of the cedar mulch had not helped his condition. He improved after the course of prednisone, with the skin hyperemia completely resolved and only a few small scabs remaining. However, this improvement only lasted for 3 wk. Skin and hair samples were sent for fungal culture, and he was bathed in an emollient oatmeal shampoo (Epi-Soothe, Virbac Animal Health, Virbac Corporation, Fort Worth, TX 76137 USA) and dipped in lime sulfur. He was also treated with prednisone (1 mg/kg p.o. s.i.d. for 14 days) again. The culture results indicated that a few colonies of Cladosporidium sp. were grown from the samples submitted, and a miconazole nitrate/chlorhexidine gluconate spray (Malaseb, DVM Pharmaceuticals, Teva Animal Health Inc., Saint Joseph, MO 64503 USA) was prescribed for twice a day application to the affected area for 14 days.

His condition worsened after 1 wk, and he was anesthetized for a full diagnostic work-up. The hair loss was bilaterally symmetric, with flaky skin and exudative dermatitis over the shoulders, hips and base of the tail. Skin scrapes were collected for microscopic examination and culture, and skin biopsies were collected for histopathology. The skin scrapes were negative for ectoparasites under microscopic examination, and the bacterial culture yielded no growth. The skin biopsy revealed multifocal marked chronic ulcerative dermatitis with a mild neutrophilic infiltrate. Blood was also collected for a complete blood count, serum biochemistry analysis, endocrine and thyroid panels, as well as allergy testing (serum IgE). The endocrine and thyroid panels are summarized in Table 1 and allergen panel results in Table 2. Complete survey radiographs were taken and revealed possible narrowing of the spinal canal at T9, near the region of hair loss. The opossum was treated with another course prednisone (1 mg/kg p.o. s.i.d. for 14 days), together with cefpodoxime proxetil (Simplicef®, Pfizer Animal Health, Pfizer, Inc., New York, NY 10017 USA; 15 mg/kg p.o. s.i.d. for 14 days). He improved dramatically on this course of medications, and the oral prednisone was continued for a further 14 days, and then weaned off over a period of seven days.

The significance of the endocrine panel results are unknown because there are no normal opossum reference values available for comparison, but the results may be useful for similar cases in the future. The total thyroxine results were within normal limits (range = 0.1–2.5 µg/dl).¹ The rest of the thyroid panel was hard to interpret due to lack of normal reference ranges, but the free thyroxine and total triiodothyronine values were at roughly the same levels as previous tests conducted on the same opossum. The allergen panel revealed significant titers to milk, and possibly liver and fleas (the test was conducted while the opossum was on prednisone, making interpretation more complicated). At this point in time, it is known for sure that the pruritis/alopecia was responsive to prednisone, indicating that pruritis was the primary problem. There remains the possibility that the prednisone relieved the pain and swelling associated with the possible spinal lesion at T9. An elimination diet will be the next diagnostic step to investigate the significance of the high IgE titer to milk and liver.

This case reveals the gaps in knowledge of disease processes in opossums, even though they have been extensively used as laboratory animals in the past. Hopefully, this case report will spark a wave of reports regarding diseases in opossums and renew interest in the only marsupial species in North America.

Table 1. Endocrine and thyroid test results for a Virginia opossum (Didelphis virginiana) with alopecia and pruritus

^aModified absorbance units (the level of allergen specific Ig detected)
^bScores ranging 0–39 indicate that no circulating allergen specific IgE was detected for the allergens tested.

Table 2. Allergen test results (food panel) for a Virginia opossum (Didelphis virginiana) with alopecia and pruritus

^aAbsorbance units (the level of allergen specific Ig detected)
^bScores ranging 0-39 indicate that no circulating allergen specific IgE was detected for the allergens tested.

Acknowledgments

I would like to acknowledge the staff of Santa Barbara Zoo for their involvement in this case, as well as Greer Labs for performing the allergy panel.

Literature Cited

1.  International Species Information System (ISIS). 2002. Physiological Data Reference Values. International Species Information System. Apple Valley, Minnesota. CD-ROM.