Of all canine parasites, heartworms are the most life-threatening. With only a few exceptions, heartworms exist throughout the United States and are rapidly becoming more and more of a problem as dogs and their owners travel throughout the U.S. carrying undetected disease with them.

Heartworms live primarily in the heart of the dog, where mature females release thousands of tiny larvae called microfilaria. These immature forms depend upon a mosquito to transfer them from one infected dog to a non-infected dog. After passing the disease to the next dog, these microfilaria develop and grow in the dog, eventually finding their way to the heart and arteries of the lungs.

     - symptoms:   Unfortunately, until the disease reaches an advanced stage, which may take months or years, dogs show few, if any, clinical signs. However, as the disease advances signs such as weight loss, loss of stamina, difficulty breathing or persistent coughing generally occur. Adult heartworms, which can reach 10-14 inches in length, can restrict blood flow to vital organs such as the lungs, liver and kidney. Left undetected and untreated, this disease is often fatal.

     - treatment:   Fortunately, there is good news. Early detection and treatment often rid the dog of the disease with minimal after-effects. Most dogs lead active, happy lives after recovery from the treatment. Testing involves a brief visit to the veterinarian; filter or serum tests, or both, are done. If negative results are obtained you should start and keep your dog on heartworm prevention year-round. If, however, your dog's test results are positive, your veterinarian will discuss treatment options with you.