Diabetes is a complicated condition caused by either an absolute or relative deficiency of insulin which results in hyperglycaemia (elevated blood glucose levels) and glycosuria (glucose in the urine). Diabetes mellitus is most common in older cats. Neutered cats, male cats and obese cats are at an increased risk of developing this condition. Genetic predisposition to diabetes is well recognised in people, and recently there has been evidence, that genetics may play a role in the development of diabetes in cats. In some countries the Burmese breed has been identified as being predisposed to diabetes, and analysis of pedigrees has suggested that this is an inherited trait.
Normal actions of insulin
Insulin is produced by the pancreas which is a small organ located in the abdomen, close to the stomach and the liver. Insulin is released into the bloodstream where it travels to all the tissues of the body. Its main role is to enable cells to take up glucose (sugar) which is needed as an energy source. Insulin also stimulates uptake of various other substances including amino acids (building blocks for proteins), fatty acids (needed for making cell membranes), potassium and magnesium by tissue cells. In the liver, insulin has important roles which include production of glycogen (a carbohydrate energy store) and fat. Insulin also reduces the amount of glucose made and released by the liver.
Diabetes mellitus
In diabetic cats, there is a relative or absolute deficiency in insulin resulting in impaired glucose uptake by tissue cells which causes hyperglycaemia. As the cells are starved of glucose, they switch to using fat and protein as an energy source. This is facilitated by breakdown of body stores of fat and protein, resulting in weight loss and the accumulation of toxic waste products which can precipitate a diabetic crisis (ketoacidosis).
An absolute insulin deficiency may arise as a direct failure of the pancreas to produce insulin. However, in most diabetic cats there is a combination of insufficient insulin secretion by the pancreas and what is known as peripheral insulin resistance. Peripheral insulin resistance describes the situation whereby cells of the body fail to respond to insulin as effectively as they should. Insulin resistance can be caused by a number of conditions including pregnancy, obesity, some drugs (eg, corticosteroids such as prednisolone, progestagens such as megestrol acetate – ‘Ovarid’;Virbac), other hormonal conditions such as hyperadrenocorticism (tumour of the pituitary or adrenal gland resulting in excessive production of corticosteroids by the body) and acromegaly (a tumour producing excessive amounts of growth hormone).
Clinical signs
In diabetic cats, the hyperglycaemia is so severe that glucose is excreted in the urine (glycosuria). Glucose takes water with it so an increased volume of urine is produced (polyuria). To compensate for this, and so that dehydration is prevented, the cat develops an increased thirst (compensatory polydipsia). Weight loss and a voracious appetite (polyphagia) are also frequently seen and these may be the original reasons for presentation to a veterinary surgeon. Therefore the main clinical signs seen in a diabetic cat are: • Weight loss • Polyphagia • Polyuria/polydipsia
These signs are not always present or may pass unnoticed. For example, the increased thirst may not be recognised if the cat is drinking from water sources outdoors while not noted to be drinking more in the home.
Other clinical signs which may be seen in diabetic cats include:
• Straining to pass urine and/or passing bloody urine associated with a bacterial urinary tract infection (bacterial cystitis) • Enlargement of the liver evident on examination by a veterinary surgeon (hepatomegaly) • Poor coat
In a small number of diabetics, the nerves supplying the legs, and in particular the hind legs, may be affected resulting in a classic plantigrade stance (sunken hocks). This is caused by a peripheral neuropathy. Very rarely, the eyes may be affected by cataracts and retinal abnormalities which develop associated with the diabetes. This can cause problems with vision, including blindness in the most severely affected cats. Systemic hypertension (high blood pressure) is a recognised potential complication of diabetes in people and has also been reported in a small number of diabetic cats.
Most diabetic cats will remain well in themselves but ketoacidosis is a potential complication that can be seen in any uncontrolled diabetic. In this situation, the cat may become extremely depressed with signs such as vomiting, diarrhoea, complete loss of appetite, dehydration, collapse and coma. If any of these signs are seen in a diabetic cat, it is cause for immediate concern and a veterinary surgeon should be contacted as soon as possible.
Diagnosis
Diabetes mellitus is suspected in cats showing the appropriate clinical signs but other diseases may also cause similar signs. For example, other important causes of weight loss in an older cat including kidney disease, cancer, hyperthyroidism (overactive thyroid gland) and inflammatory bowel disease need to be ruled out. The earlier that diabetes can be detected the better and so routine urine checks in cats above 7 years old are recommended.
Blood and urine tests are required to confirm a diagnosis of diabetes. Although hyperglycaemia and glycosuria are found in diabetic cats, cats can also suffer from a stress-associated hyperglycaemia which can cause glycosuria and therefore confuse diagnosis. For this reason, a single blood or urine sample cannot be considered as diagnostic of diabetes. One solution to this problem is for the cat’s owner to collect a urine sample whilst the cat is in its non-stressful home environment. The easiest way of doing this is to replace normal cat litter with non-absorbent cat litter (supplied by a vet) so that a sample can be collected. The urine sample can be taken to a veterinary surgeon for testing or the hospital may give you some test strips to use at home. Another solution is to measure the blood levels of fructosamine which more accurately reflects the long-term blood sugar levels and so may help to distinguish between stress-associated hyperglycaemia and diabetes mellitus. Fructosamine is a glycosylated serum protein molecule which is present in higher concentrations when the blood glucose concentration is high. An elevation in serum fructosamine indicates that there has been significant hyperglycaemia during the previous two to three weeks. This test can also be used for long-term monitoring of how well stabilised a diabetic cat receiving therapy is.
Treatment options
Diabetes mellitus is usually a treatable condition and although it requires considerable dedication and commitment from owners, it can be a very rewarding problem to manage.
Feline Leukaemia (FeLV) is from the same virus group as Feline Immunodeficiency Virus (FIV) and is also similar to HIV in humans. As well as causing tumours, FeLV damages the cat’s immune system, making them susceptible to other infections. It is spread via cat-to-cat contact and is more common in multi-cat households. Kittens can also catch the virus from their mothers, either in the womb or via infected milk.
Looking After the older Cat
The best types of cat toys are those that encourage chasing and hunting-type behaviour. Toys that do this are those that move quickly and unpredictably. Good examples are fishing rod-type toys, or balls intended for cats and kittens. Suitable cat toys are available from most pet shops, pet supermarkets and Rosegreen Pet Supplies.
Example of a cattery is the late 1960s
of animals, but thankfully, the light of knowledge and experience has swept across most areas. This enlightenment is due in no small part to FAB and the vision of Joan Judd, Sophie Hamilton-Moore and their colleagues.