Heartworm is a very serious disease that may result in heart failure and/or complications which usually prove fatal. Most people in the U.S. must give their dogs preventative medicine to protect them against heartworm. Heartworms live in the dog’s heart and damage the heart and lungs. Heartworm larvae are spread from infected dogs to healthy dogs by mosquitoes. In high incidence areas such as the southeastern United States, both dogs and cats are at higher risk for heartworm disease and cats need to be on heartworm preventative too.

Heartworm infection is easily prevented but can be difficult as well as costly to cure. Currently, we recommend that our canine patients receive heartworm preventative once monthly beginning at age nine weeks year round. Cats do not need to be on heartworm preventative because we are a low incidence area.

Traveling increases your pets’ risk. Areas with standing water such as irrigated fields, rivers, ponds, and lakes increase the risk of mosquitos and therefore heartworm disease. Greatest transmission of disease occurs in late summer. Even indoor pets are at risk.

Diagnosis is accomplished through a blood test in order to find the microfilariae, but occasionally a chest x-ray may be required. Dogs need to be tested for heartworm before they are started on preventative medicine except for puppies less than seven months of age. Dogs that are receiving preventative medicine, as directed, need to be tested every 3 years.

Testing recommendations sometimes need to be tailored to the patient’s individual situation. For example, a patient that has missed four or more months of preventative medicine may need to be tested twice – right then and also seven months later. Dogs that travel through Heartworm endemic areas (most of the United States) should be tested annually. Dogs that move here from a Heartworm endemic area should be tested 7 months after they arrive here. Please see the Merial Heartgard Guarantee for their required testing guidelines.

Heartworm Disease not only reduces the patient’s quality of life but also their lifespan, from months to years shorter. This is what makes Heartworm testing and preventative medicine worth it.