Heartworm disease is a serious yet preventable disease spread by mosquitoes. A female mosquito ingests heartworm larvae from an infected dog while obtaining a blood meal. The larvae further develop inside the mosquito, and then the mosquito injects more mature larvae into another susceptible dog. This dog becomes infected with heartworm disease.

The heartworm larvae migrate in the dog's body from the area of the mosquito bite and eventually enter the dog's blood. Adult heartworms develop in the right side of the heart and major lung blood vessels, causing damage to these vessels and obstructing normal blood flow. Over 250 adult worms may develop in a dog's heart and vessels. Direct infection from dog to dog does not occur. The heartworm larvae must develop inside the mosquito to reach their infective stage.

Many dogs do not have symptoms of heartworm disease until severe infection occurs. Common early symptoms include coughing and difficulty breathing. Decreased ability to exercise, abdominal swelling, and muscle wasting occur as the disease progresses. Finally, death results from heart failure.

Treatment of heartworm disease is not without risk, and each dog must be thoroughly evaluated to determine the likelihood of treatment complications. Treatment is also expensive.

The treatment protocol consists of two phases. During the first phase, the dog is given medication to kill the adult heartworms. Any physical exertion must be prohibited for several weeks following this treatment. The second phase of treatment occurs several weeks later when medication is given to the dog to kill the heartworm larvae. The dog is subsequently placed on heartworm prevention.

Heartworm disease is an illness that can be easily prevented. Heartworm preventives are available as daily or monthly chewable tablets. Most heartworm preventives also provide some protection against some intestinal parasites.

Dogs over 6 months of age should be confirmed heartworm-negative by a simple blood test before beginning any type of heartworm prevention. Year-round prevention is recommended in climates that support year-round mosquito activity.

"An ounce of prevention is worth a pound of cure" certainly applies to heartworm disease.

By taking simple preventive measures, your dog will live a much longer, healthier, happier life. See your veterinarian for further information and recommendations regarding heartworm prevention in your area.