Diabetes mellitus is an endocrine disease that manifests as an inability of the animal's body to utilize carbohydrates (sugars) properly. This occurs either because the pancreas does not manufacture sufficient quantities of the hormone the body requires for this function (insulin) or because the body's cells no longer recognize it properly.
The upshot of this fundamental aberration in carbohydrate utilization is that these basic, energy providing nutrients (sugars) are not able to enter the body's cells to "feed" them. Instead, they linger in the bloodstream while the body itself literally starves.
By way of handling this starvation state, the body does things like start to break down all its tissues, fats first, to attempt to generate energy with which to feed itself. In the absence of the insulin required to allow sugars to gain entry to the cells, these efforts typically lead to a dangerous metabolic state called ketosis. Moreover, when sensitive tissues like the brain don't receive the required amount of energy, serious neurologic disruption--and death--can ensue.
Diabetes mellitus is considered a multifactorial disease in origin, meaning that a variety of factors play into its individual acquisition. While obesity is considered to be a primary risk factor for diabetes in cats, drugs (such as corticosteroids) and genetic predisposition is considered to play a role as well, despite the fact that its mode of inheritance is poorly understood.
In dogs, however, genetic predisposition to diabetes mellitus seems to play a larger role than obesity or exposure to certain drugs. At the very least, the genetics of canine diabetes has been better studied than for felines. Diabetes mellitus in the keeshond, for example, has been determined to be inherited as an autosomal recessive trait. Indeed, the most severe forms of the disease have been identified in dogs as young as six months of age and its genetic origins in these cases are undisputed.
Symptoms and Identification
The most obvious, initial symptoms of diabetes revolve around excessive thirst and urination along with appetite increase paired with weight loss.
Excessive thirst and urination happens because the huge quantity of sugar in the bloodstream "spills" into the urine and "pulls" water out of the bloodstream along with it, thereby dehydrating an animal should insufficient drinking occur. Due to the high levels of bacteria-attracting sugar in the urine, urinary tract infections are a routine finding, as well.
Increased appetite and weight loss happens because the body is unable to effectively use the food it takes in as energy. Hunger is never satisfied despite a typically ravenous appetite and weight loss is almost always a feature.
Diagnosis is achieved through bloodwork revealing high blood sugar levels along with urinalysis confirming the presence of sugar in the urine. Ketones, the breakdown product of aberrant fat metabolism may also be detectable in the urine.
Predisposed breeds include:
Long-term, the treatment of choice in dogs requires the administration of injectable insulin to drive sugar molecules into the body's needy cells. Dietary changes will also help. They temper sudden spikes in sugar levels with lower glycemic index ingredients. In cats, weight loss and dietary changes will often suffice for long term treatment of diabetes. In dogs, particularly for those that suffer less environmentally-influenced forms of diabetes, insulin is almost always required long-term.
Short-term, most patients will require hospitalization. Some may even need intensive care should their presentation be complicated by a variety of other problems secondary to the diabetes (this is a common scenario).
If specialist-quality intensive care is required in the short term, some diabetics can readily rack up veterinary bills in the five to ten-thousand dollar range. Most, however, are expensive to handle at the time of the initial diagnosis ($500 to $3,000) but will become more manageable as time progresses. Including the cost of insulin, syringes, veterinary monitoring and the premium paid in prescription pet foods, most diabetic pet owners should expect to pay an average of $100 to $200 every month.
Keeping pets a healthy weight and eliminating risk factors like corticosteroid drug therapy are helpful. For severely genetically predisposed dogs, however, the disease is not preventable except by means of limiting access of affected or carrier animals to the gene pool. In keeshonds, both parents of affected dogs are always considered carriers. For keeshonds as well as for other breeds, affected dogs and their first degree relatives should not be bred.
Nelson, R.W. 1995. Diabetes Mellitus. In S.J. Ettinger and E.C. Feldman (eds.). Textbook of Veterinary Internal Medicine, p. 1510-1537. W.B. Saunders Co., Toronto.