Q. I just moved to New Jersey from Georgia. In Georgia, my veterinarian always recommended heartworm preventative because it is a common disease there. Do I still need to give my dog heartworm preventative every month in this area?

Heartworms (Dirofilaria immitis) are parasites that can infect the bloodstream of dogs and cats, as well as other animals. They are spread by mosquitoes. Once an infected mosquito bites your dog, the immature heartworms, or larvae, mature in the blood and travel to the pulmonary artery, one of the main vessels leaving the heart.

Heartworms can cause severe damage, even if your dog is not showing any external signs. Most commonly, they cause damage to the lungs as the worms travel out of the pulmonary artery into the lungs. As the body tries to attack the worms, the immune response can also lead to problems like kidney disease and clotting abnormalities. With severe infections the heartworms can extend to the inside of the heart, occupying the space that normally fills with blood. If there are enough worms this can cause caval syndrome, a life threatening situation where the worms prevent the heart from functioning normally and can cause an abnormal build-up of fluid in the body.

Since heartworms need mosquitoes to be transmitted, heartworm disease is more prevalent in areas with heavy mosquito populations, like Georgia. It can, however, exist anywhere mosquitoes live and it does exist in the New Jersey/New York area.

Heartworm disease is easily preventable by administering a monthly heartworm preventative tablet. Since the disease can cause so many problems and the treatment is very costly and associated with many side effects, it is highly recommended to give your dog a heartworm preventative on a monthly basis. Heartworm preventatives are typically very safe and most also protect against various types of intestinal parasites. If there has been a period of time when your dog was not receiving preventative, it is important that your dog be tested for heartworm disease before starting preventative again since there can be reactions when the preventative is given to dogs with heartworms.

— Jennifer Mulz

DVM