Canine heartworm disease develops when a dog is bitten by a mosquito carrying microscopic larvae of a parasite called Dirofilaria immitis. As a mosquito feeds, these microscopic larvae infect and begin their migration into the dog’s bloodstream, where they grow into adult worms. Adult female heartworms are larger than male heartworms and can grow 10 to 12 inches in length. They make their home in the right side of the heart and vessels of the lungs, often causing lung disease and heart failure. Although easy to prevent, heartworm disease continues to be a major health problem for dogs living in the United States and wherever mosquitoes live. If you ever see or get bitten by mosquitoes, your dog is at risk!

A heartworm test is simple and only requires a small blood sample from your pet. It works by detecting the presence of heartworm proteins. The test may be read right at the hospital or sent out to a laboratory. If a pet tests positive, further tests may be ordered. Yearly testing is the standard of care and is recommended by the American Heartworm Society.

Heartworm preventive medications are very effective when given properly on the prescribed schedule. It is important to monitor your pet’s weight to ensure your pet falls within the weight range listed on the package. All approved heartworm preventives are typically safe, very easy to use, relatively inexpensive, and some provide treatment for additional parasites. Prevention is always safer and more affordable than treating adult heartworm infections. It is your responsibility to faithfully give your dog the preventive medication as prescribed. The best way to reduce the risk of heartworm infection in your dog is to give the preventive medication year-round. Be certain to have all dogs 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. Routine testing is critical to avoid a delay in detecting early infection and starting life-saving therapy.