Diabetes is a complicated condition caused by a deficiency of insulin which results in elevated blood glucose levels and 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, particularly from Australia and New Zealand, that genetics may play a role in the development of diabetes in cats. In these 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 . Glucose takes water with it so an increased volume of urine is produced. To compensate for this, and so that dehydration is prevented, the cat develops an increased thirst. Weight loss and a voracious appetite 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
• Increased appetite
• Increased drinking and urinating

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
• 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). 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. 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 (see later).

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) or clean aquarium gravel 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.

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.

Management of predisposing factors
Initial management may involve addressing factors which have precipitated or complicated the diabetes such as treating obesity or withdrawing drug therapy. If no predisposing causes of the diabetes can be identified, or if correction of these do not lead to resolution of the diabetes, then specific treatment is required.

Dietary management of diabetes
Underweight diabetic cats may need energy dense diets until their weight normalises. Obese diabetic cats should be put onto a weight loss regime, under the guidance of a veterinary surgeon, as obesity interferes with the way insulin works. In some of these cats, this may resolve the diabetes.

Research has shown that low carbohydrate and high protein diets can help to reduce the requirements for insulin and improve diabetic management. A variety of commercial petfood manufacturers produce prescription low carbohydrate diets suitable for use in diabetic cats.

It is recommended, as far as possible, to keep the diet constant both in terms of what is fed as well as timing of meals and so on. Altering the feeding regime may upset the stabilisation of the diabetes. However, it is not necessary to feed cats at strict meal times - it is fine to stick to the feeding regime that your cat is already used to.

Insulin therapy
In most diabetic cats, insulin therapy is required, at least initially. Insulin is given by an injection under the skin of the scruff and most cats will be stabilised on a regime involving either once or twice daily injections. The exact site of administration should be changed on a daily basis to reduce any scarring or reaction at the injection site which may limit insulin absorption. Special insulin syringes with very fine needles are used so that the cat will hardly feel the injection. Veterinary surgeons often recommend that diabetic cats are offered food just before they receive their insulin so that the cat is distracted by eating and does not notice the injection.

There are a number of different types of insulin available and different cats respond better to one type than another. The dose required by each cat is also very variable and it may take several weeks to stabilise the diabetes. Many veterinary surgeons will hospitalise diabetic cats undergoing initial stabilisation.

Prognosis
The long-term outlook for cats with diabetes mellitus varies according to how old they are, how easy it is to stabilise their diabetes, whether they have any other diseases and how severe these are. In one study, the average survival time for diabetic cats was around 2 years. Many diabetic cats have an excellent quality of life and are extremely rewarding cases to treat.

Hyperthyroidism (overactive thyroid glands) is a very common disorder of older cats. It is caused by an increase in production of thyroid hormones from the thyroid glands, which are situated in the neck. Clinical signs associated with hyperthyroidism can be quite dramatic and cats can become seriously ill with this condition. However, in most cases hyperthyroidism is treatable and most cats will make a complete recovery.

Thyroid hormones have an important role in controlling the body's metabolic rate and thus the general activity level, so cats with hyperthyroidism tend to burn up energy too rapidly and typically suffer weight loss despite having an increased appetite and increased food intake.

In the vast majority of cases the increased thyroid hormone production is due to a benign (non-cancerous) change. Both of the thyroid glands are involved, although one gland may be more severely affected than the other. The abnormal thyroid tissue becomes enlarged, but the underlying cause of this change is currently unknown. Cats usually respond extremely well to treatment, and if the condition is recognised early and treated appropriately, then the outlook for the affected cat is generally very good.

A malignant (cancerous) tumour known as a thyroid adenocarcinoma can also be an underlying cause of some cases of hyperthyroidism. Fortunately this is rare, and is only the cause in around one to two per cent of all hyperthyroid cats. When a thyroid adenocarcinoma is present treatment is much more difficult.

Typical clinical signs

Hyperthyroidism is almost exclusively seen in middle- to old-aged cats, and is rarely seen in cats less than seven years of age. Male and female cats are affected with an equal frequency and although no studies have shown any breeds that are particularly prone to developing hyperthyroidism, there is some evidence that it is less common in Siamese cats.

Cats affected with hyperthyroidism usually develop a variety of clinical signs, which are usually quite subtle at first, but then become more severe as the disease progresses. Also, as this disease occurs mostly in older cats, some affected cats will have other diseases that can complicate and even mask some of the clinical signs.

The 'classic' signs of hyperthyroidism are:

• weight loss, usually despite an increased appetite

• increased thirst

• increased irritability

• restlessness or even hyperactivity.

• many affected cats have a rapid heart rate

• an unkempt coat

• mild to moderate diarrhoea and/or vomiting is also quite common

• affected cats will be noticeably intolerant of heat and seek out cooler places to sit, and some (especially advanced cases) may pant when they are stressed.

• most hyperthyroid cats will show some degree of polyphagia (excessive appetite) and restlessness, but in some advanced cases there will be generalised weakness, lethargy and loss of appetite and the signs will be less characteristic.

SKIN PROBLEMS

Recurrent skin infections generally have an underlying cause. As the inner ear is simply a continuation of the skin surface, anything which is affecting the skin can also affect the ears, and predispose them to becoming infected.

The major causes of skin problems are:

Allergies – there are 4 main causes of skin allergies. An animal with one allergy is likely to be allergic to other things as well. The 4 main allergens are:

• Atopic dermatitis – along with a flea allergy this is the most common type of allergy in dogs. This is an allergy to substances in the air, including pollens, house dust mite faeces, molds and animal sources such as cat saliva. It generally causes a seasonal pattern of skin problems and begins at 1-3 years of age.

• Flea allergy dermatitis – this is an allergy to the saliva of fleas. In dogs it typically causes lesions over the tail and down the back legs. It can present in many ways in cats, often with lesions in front of the ears or scabs over the body from scratching. It is the most common skin allergy in cats.

• Food allergy – an allergy to food can cause skin signs. The animal will often be vomiting or have diarrhoea as well, but they will not always have gastrointestinal signs.

• Contact allergy – animals can be allergic to almost anything they come into contact with. A plant called Wandering Dew is a common cause of contact allergies.

The allergies that we have some control over are food and flea allergies. A special hypoallergenic diet can be trialled for 8 weeks to determine whether food is a likely cause, and strict flea control with a good quality flea treatment is used to eliminate any response to fleas. (All pets in the household will need to be treated and possibly the house if flea numbers are a problem)

Sometimes by controlling these 2 allergens there will be a reduced reaction to other allergens.

Mange – this is a mite infestation of your pets skin.

It is diagnosed by obtaining a skin scraping and looking for the presence of mites.

Treatment depends on the type of mite found.

Hormonal imbalances can also cause skin signs. The type suspected will depend on the lesions present. There will typically be other signs present, but this will depend on the type of hormonal imbalance present. Diagnosis is through blood tests.

Treatment for skin problems can be on-going. Therapeutic options include:

• Specific treatment if an underlying cause is able to be identified. Unfortunately this is not always possible.

• Antibiotics to treat any skin infections, as infection will cause itchiness and worsen the signs.

• Shampoos to reduce allergens on the skin surface and to moisturise the skin.

• Avoiding known sources of contact allergens.

• Steroids or other immunomodulators, to modify the allergic response.

• Diet, there are several prescription diets available to support the skin and help reduce symptoms.

OBESITY

Obesity is the second most common disease seen in cats and dogs and is a serious medical condition. It is a systemic disease, with metabolic, hormonal and immunological changes. It is associated with an increased risk of many diseases including:

• osteoarthritis

• cruciate ligament rupture

• cancer, especially mammary tumours in female dogs

• skin disease

• diabetes mellitus

• pancreatitis

• tracheal collapse

• dystocia (difficulty giving birth)

• hepatic lipidosis (liver infiltrated by fat)

• hypertension (high blood pressure)

• idiopathic cystitis in cats

The only body change that has been shown to increase an animals lifespan is being lean. Being lean can increase the lifespan of an animal by 2 years, and will also result in better health during their life.

Weight loss should be slow, with an aim of 1-2% weight loss per week. An excessive rate of weight loss results in a reduced metabolic rate, reduced rate of weight loss relative to the predicted rate of weight loss, loss of muscle mass and weight gain once the diet is stopped. There are several strategies to produce weight loss:

• Feed 80% of the amount that is currently being fed – this is usually effective as each animal has an individual metabolic rate, just like each person has an individual metabolic rate. This can be difficult if you have an animal that begs for food. This needs to include every food source, as treats given to animals can have a high caloric density, and what would be a small amount for a human can be a huge increase for a cat or dog.

• Feed a low calorie diet – there are several diets available that have a reduced calorie quantity. These diets enable you to feed a similar volume of biscuits, and reduces begging for food by your pet. Weight loss diets are generally low fat, high fibre, high water diets to provide low caloric density and high bulk, decreasing hunger.

• Moderate exercise – this can be walking, swimming, playing with balls or kongs (balls that can be filled with food so the animal needs to roll the ball around to get the food out), or toy mice or a light for cats. Excessive exercise can lead to a compensatory food intake and can cause joint damage in overweight animals so should be avoided.

A weight loss programme is always easier to stick to when you can see that you are getting results. Tracking the weight loss can be done by weighing the animal once a fortnight. Remember, weight loss should be slow, so it will take some time for the results to be seen, but it is well worth it. You control what food your animals get, so you have complete control over the weight they are.