Case study: Iatrogenic diabetes mellitus in a koala (Phascolarctos cinereus) receiving treatment with prednisolone
Lathe, SE 2016, Journal of Wildlife Rehabilitation, vol. 36, no. 2, pp. 7-10.
A female koala that was brought into a wildlife hospital developed diabetes mellitus during treatment with prednisolone. After cessation of prednisolone treatment, blood glucose levels in the koala decreased to below the nominal reference range.
Physical examination of the koala upon admission to the hospital revealed extensive dermatitis over the body, along with excessive salivation due to unknown causes. Subsequent testing of the affected areas of the skin identified a mixed infection of Malassezia species along with unidentified Gram-positive cocci. To treat the bacterial-fungal mixed infection, the koala was given a treatment course of oral trimethoprim-sulfamethoxazole (TMS) and nystatin, along with prednisolone for relief of severe itching caused by dermatitis. At day one of treatment, the initial blood glucose of the koala was observed at 4.82 mmol/L, well within the reference range of 2.7 – 7.2 mmol/L. At day seven, the blood glucose levels had increased to 20.01 mmol/L, with urinalysis observing glucose in the koala’s urine, indicative of diabetes mellitus. Treatment with prednisolone was ceased on day 13 of the treatment course, while anti-fungal and -bacterial medications continued to be given to the koala. A decrease of blood glucose levels to 1.2 mmol/L was observed on day 19 of treatment.
Throughout the course of treatment, the koala exhibited weight loss, polydipsia and lethargy, which have been attributed to diabetes mellitus. While there were improvements in the skin condition of the koala, the cause for continued excessive salivation was never identified. Coupled with the continued weight loss, the prognosis of the koala was determined too poor and the koala was euthanised after a month of treatments. Samples taken for a post-mortem examination determined that the pancreas and adrenal gland had no histological abnormalities. For type 1 diabetes in humans and canines, inflammation of the pancreas usually occurs, resulting in histological changes. TMS and nystatin had not been previously reported to induce changes in the blood glucose levels. Hence, rather than an auto-immune condition causing diabetes, it was suggested that the prednisolone treatment had reduced secretion of insulin, induced insulin resistance, or a combination of both.
This study documents the first time that diabetes mellitus in a koala was reported to be induced by a glucocorticoid. It is possible that diabetes mellitus may be an unrecognised consequence of treatment with glucocorticoids in koalas. As this study indicates the susceptibility of koalas to the development of diabetes mellitus while being treated with prednisolone, additional clinical management strategies are required, such as regular blood glucose analysis and urinalysis. Additionally, glucocorticoid treatment should only be used when necessary.
Summarised by Daniel Chew
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