Heartworm Disease

July 2012, Dr. Bridget Overbey, DVM

Heartworm disease is a serious and potentially fatal condition of dogs and cats caused by a parasitic worm that spreads through the bite of infected mosquitoes. Once bitten by an infected mosquito, the heartworm larvae develops into an adult worm over several months and travels to the lungs, arteries, and heart of the infected animal. While it is rare for dogs and cats that have never traveled outside of Washington to become infected with heartworms it has been diagnosed in all 50 states and is endemic in parts of Oregon. Nearly all dogs exposed to heartworm larvae will develop adult worms, and more than 30 worms can be present in the heart of an infected dog. While cats are slightly more resistant to infection, 60-90% of exposed cats developing adult worms, they are much more sensitive, and even 1 or 2 worms can be fatal. Signs of heartworm disease include coughing, fainting, tiring easily, and even heart failure. Due to the spread of heartworm disease and its serious complications the American Heartworm Society recommends yearly testing for dogs and cats beginning at six months of age while keeping pets on year round heartworm preventative. Fortunately there are several options for monthly heartworm preventative for dogs and cats. Revolution is a topical monthly medication approved for both dogs and cats that is also effective for flea, ear mite, and some tick control. Trifexis is a monthly chewable heartworm preventative for dogs that also kills adult fleas, roundworms, hookworms, and whipworms. Heartgard is also a monthly chewable medication available for dogs and cats that prevents heartworm infection, as well as treating some intestinal parasites. If you have any questions about any of these medications or heartworm disease please talk to your veterinarian. Dr. Bridget Overbey, DVM