Spontaneous diabetes mellitus is rare in the ferret and poorly characterized from a pathological point of view. Diabetes may be a rare, usually transient, complication of pancreatectomy performed for the treatment of an insulinoma. Subjects with adrenal disease sometimes have persistently raised glycaemia, although this resolves after surgical or medical treatment of the adrenal pathology. Diabetes is characterized by low levels of insulin in the blood stream or by the development of resistance to insulin, with a consequent impairment in the metabolism of fats, proteins and carbohydrates.
CLINICAL SIGNS
The classical clinical signs of diabetes mellitus are polyphagia, polyuria/polydipsia, lethargy and weight loss; in severe cases there may be cataracts and diabetic neuropathy with weakness and ataxia.
DIAGNOSIS
The diagnosis is based on finding blood glucose levels persistently above 400 mg/dl (usually the levels exceed 500 mg/dl), with glycosuria. Ketonuria may be found in animals with ketoacidosis.
The hyperglycaemia due to diabetes should be differentiated from the transient abnormality associated with stress; in the latter case, there is no glycosuria and the levels of glucose in the blood, albeit raised, are not usually very high. In doubtful cases the blood test can be repeated, trying to minimise the stress to the animal while taking the sample. The value of assaying fructosamine, useful for establishing whether the hyperglycaemia is chronic, has not yet been validated in the ferret.
A complete blood count, X-rays and ultrasound studies are useful for evaluating the presence of concomitant disorders, although not for the diagnosis of diabetes. Before starting treatment, it is important to exclude the presence of adrenal disease as the cause of hyperglycaemia.
TREATMENT
The treatment of diabetes in the ferret is not standardised and has been extrapolated from that used in the cat. One suggested protocol consists of slow or ultraslow insulin, starting with 1 U per ferret every 12 hours and then increasing the dose until glycosuria or ketonuria disappears. The owner should be instructed to test the urine daily with a dipstick to determine the presence of glycosuria or ketonuria, thereby indirectly confirming the hyperglycaemia, before administering the insulin. Some owners are able to monitor the glycaemia itself periodically, using a specific hand-held instrument to test a drop of blood obtained by pricking the animal’s footpad with a lancet. The animal’s diet should be of excellent quality, rich in proteins and contain little or no carbohydrates.
If the hyperglycaemia appears after a partial pancreatectomy, usually no therapy is needed and the condition resolves spontaneously within a few weeks.