What is Heartworm Disease?

     Canine heartworm disease develops when a dog is bitten by a mosquito carrying microscopic heartworm larvae (juvenile worms) of a parasite called Dirofilario immitis.  As a mosquito feeds, these microscopic larvae are deposited on the dog and quickly penetrate the skin to begin their migration into the dog’s bloodstream.  Adult heartworms can grow 10-12 inches in length and make their home in the right side of the heart and pulmonary (lung) arteries, often causing lung disease and heart failure.

Who should be tested?

     Annual testing is recommended for monitoring the success of any heartworm prevention program. All dogs more than six months of age should be tested for heartworms prior to initiating a preventive program. Heartworm preventives are effective when given properly and on a timely schedule.  It is important to note that these medications are quickly eliminated from a dog’s body shortly after they are given and do not continue to protect the dog from future infection.  Instead, they eliminate infections acquired since the last dose.  All approved heartworm preventives are highly effective, safe, easy to use, relatively inexpensive, and often provide treatment for additional parasites.  Prevention is always more safe and affordable than treating dogs with adult heartworm infections.

     Please remember, it is your responsibility to faithfully maintain the program you have selected in consultation with your veterinarian.  The best way to eliminate the risk of heartworm infection in your dog is to institute a year round prevention program.

     Be certain to have all pets tested prior to initiating or restarting any heartworm prevention program, as administration of some preventives can cause life-threatening reactions when given to heartworm-infected pets.

            prepared by American Heartworm Society