SCRATCHING THE SURFACE OF CANINE SKIN DISEASE

by Dr. Rob Hilsenroth,Morris Animal Foundation

The skin is the largest organ in an animal's body. The unique design of the skin allows it to perform many important functions. Most of the skin is soft, pliable and covered with hair. In certain areas, however, the skin is custom-made to perform specific functions, such as that of the nose and the foot pads of the paws. Skin has the remarkable ability to heal if damaged or to regrow if removed. Skin can even be surgically removed from one area of the body and placed in another site to grow É a process called grafting.

What is the function of skin?

The primary purpose of skin is to protect the body from insults like trauma and microorganisms. The skin is also responsible for keeping the dog warm. It does this by producing hair and maintaining an insulating layer of fat. Specialized skin of the paw pads and tongue allow dogs to cool themselves by letting moisture evaporate.

The skin helps regulate the body's moisture balance by creating a barrier to the outside environment. It keeps itself pliable by producing oils from the glands called sebaceous glands, which are located all over the body. Skin oils also contribute to the external barrier against bacteria.

The skin is a sensory organ as well; it contains nerve endings called sensory receptors to provide touch and pain sensation. It's very easy to take the skin for granted, but it's critical to an animal's survival.

What kinds of skin diseases can a dog get?

Like any other tissue in the body, the skin is subject to disease. Despite the wonderful versatility of the skin, it has only a small number of ways to respond to insult or injury. Disorders of the skin are often challenging for the veterinarian to diagnose since many skin diseases look very much alike. In addition, the skin can often be affected by disease occurring elsewhere in the body. This is referred to as secondary skin disease.

Skin that is unhealthy can either be dry and flaky, or greasy with a strong odour. When the skin is unhealthy, the dog's coat is usually affected. Hair may fall out, creating bald patches, or the hair may be brittle and dull. Irritated skin is often red and ÒangryÓ looking. Small raised bumps or crusty scabs may appear. Diseased skin is uncomfortable and may cause a dog to scratch excessively, damaging the skin further. Chronically irritated skin can change colour and become wrinkled and tough.

A common disease of dogs is called seborrhoea. Seborrhoea refers to the rapid death and subsequent new production of skin cells. Skin cells normally die off and are replaced at a relatively rapid rate as compared to other tissues in the body. But the normal rate of turnover is accelerated with this disease. Seborrhea results in dry, flaky skin (seborrhoea sicca) or greasy, foul-smelling skin (seborrhoea oleosa). These conditions allow the skin to become easily infected with bacteria and yeast which further skin damage and increase the affected dog's discomfort.

What causes seborrhoea?

Seborrhoea is a skin disease that is often secondary to problems such as allergies, poor nutrition, mange, hormone deficiencies or hormone excess. In these cases, if the underlying disease is diagnosed and treated or cured, the seborrhoea will greatly disappear.

Some dogs are unfortunate enough to be born with seborrhoea as a primary disease. In these cases, no underlying cause for the disease can be found. Primary seborrhoea is believed to be an inherited disorder. It is seen often in the Spaniel and Terrier breeds, and less commonly in Labrador Retrievers, Doberman Pinschers and Chinese Shar-Peis. At this time, there is no cure for this disease and dogs must be carefully managed their whole lives to keep them comfortable.

How can primary seborrhoea be treated?

Dogs with primary seborrhoea are usually treated with shampoos. Owners often need to bathe their dogs two to three times a week with therapeutic shampoos just to control the symptoms and try to prevent skin infections. Skin infections invariably occur, however, requiring treatment with antibiotics. A group of drugs called retinoids, which are derived from vitamin A, have been tried for the treatment of primary seborrhoea with variable results. These drugs are very expensive and may have undesirable side effects including eye and liver problems.

What is being done for dogs with primary seborrhoea?

Morris Animal Foundation and the Golden Retriever Club of America recently funded Dr. Ken Kwochka's study at the Ohio State University College of Veterinary Medicine. The study, "Treatment of Canine Idiopathic Seborrhoea with 1,25-Dihydroxyvitamin D3" explored the possibility of using a drug called calcitrol (a vitamin D derivative) to control the symptoms of primary seborrhoea in dogs. The results of Dr. Kwochka's work suggest that calcitrol may be a new and safer alternative to the retinoids for dogs with this chronic, uncomfortable disease.
Rob Hilsenroth, DVM, is Executive Director of Morris Animal Foundation. This nonprofit organization sponsors animal health studies at veterinary schools and institutions throughout the U.S and in other parts of the world. All annual unrestricted contributions to the foundation support health programs not the cost of administration or fund-raising.

If you'd like to make a contribution, write Morris Animal Foundation, 45 Inverness Drive East, Englewood, CO 80112.
For more information, please call (800) 243-2345.