Management of spontaneous diabetes mellitus in a companion rat (Rattus norvegicus)

Background

Rats are a common model for diabetes mellitus in humans, but spontaneous diabetes in pet rats has not been described.

Case Description

A 1-year, 5-month-old, intact male domestic rat (Rattus norvegicus) was evaluated for polydipsia and weight loss. Diagnostics revealed glucosuria and hyperglycemia (414 mg/dL; normal 89–165 mg/dL) consistent with diabetes mellitus. Hypercholesteremia and elevated liver enzymes were also noted. Treatment with glipizide (0.5–1 mg/kg, orally, every 12 hours), metformin (50–150 mg/kg, orally, every 12 hours), and intermediate-acting porcine insulin (1–3 units, subcutaneously, every 12 hours) were ineffective at producing normoglycemia. Long-acting glargine insulin (1 unit, subcutaneously, every 12 hours) resulted in improved body weight and longer periods of normoglycemia for 3 months. Eleven months after diagnosis, the rat presented with rapid weight loss and tail necrosis; euthanasia was elected. On histopathology of the pancreas, the few visible islets and lack of amyloid production was considered more consistent with insulin-dependent (type I) diabetes mellitus than insulin-independent (type II). Other necropsy findings included bronchopneumonia, radiculoneuropathy, skeletal muscle necrosis of the tail, and chronic renal disease.

Conclusions and clinical relevance

Although uncommon, diabetes mellitus should be considered in pet rats presenting with polydipsia, polyuria, and weight loss. Insulin therapy may be useful for treatment of diabetes mellitus in pet rats but requires careful monitoring and further evaluation.