5 Facts Pet Parents Need to Know About Protecting Pets From Heartworms

April 17, 2025 at 01:00 AM EDT

SPONSORED CONTENT -- (StatePoint) Heartworms are one of the most common and serious health threats faced by pets. According to the American Heartworm Society, more than a million U.S. pets are infected with heartworms, and incidence numbers are rising—even though heartworms are easily prevented. To equip pet parents to provide the protection their four-legged family members need this summer and year-round, the American Heartworm Society is sharing five vital facts about this deadly threat.

1. A single infected mosquito can spread heartworms to multiple pets. Heartworms aren’t spread from one pet to another. Instead, they are transmitted when a mosquito feeds on an infected animal, such as a dog, coyote, fox or wolf, then later feeds on other susceptible animals and pets. Within months, heartworms grow from tiny larvae into foot-long adult worms that live in pets’ hearts, lungs and blood vessels.

2. Heartworms are found throughout the United States. Warm, humid locales such as the Gulf States and Southeastern U.S. are widely known as hotbeds of heartworm infection, thanks to the presence of mosquitoes that thrive in these conditions. However, heartworms have become increasingly common in regions such as the Southwest, Pacific Northwest, Upper Midwest and New England. One factor supporting broader transmission is the practice of transporting homeless dogs for adoption from areas of the country where heartworms are extremely common to locales that formerly had few cases. Studies also suggest that mosquitoes prefer feeding on pets with heartworms over pets that don’t harbor them. Finally, mosquitoes are opportunistic pests that require only small amounts of standing water—including puddles or half-full watering cans—to breed.

3. Heartworms aren’t just going to the dogs. While dogs are highly susceptible to heartworm infection, cats and ferrets get heartworms, too. One thing all three species have in common is that they can become very ill, and even die, if infected with heartworms. That’s why the American Heartworm Society recommends heartworm screening and year-round prevention for all pets.

4. There’s no “season” for heartworms. While the risk of heartworm spread is greatest for pets from spring through fall, experts advise that pets be maintained on heartworm prevention year-round. Estimating when the first and last mosquito of the so-called season will appear is a dangerous guessing game, given the volatility of weather conditions in even the coldest parts of the country. Furthermore, buildings, parking lots and other structures in city and suburban communities can create sheltered “heat islands” with significantly warmer conditions than surrounding open areas. Mosquitoes also survive and thrive by relocating indoors or taking refuge in garages and crawl spaces when temperatures drop.

5. Prevention beats treatment every time. While heartworms in dogs can be treated, treatment can be expensive and requires multiple veterinary visits and months of activity restriction. Cats and ferrets, meanwhile, have no medications to cure their heartworms, because the treatment used in dogs is not safe for them. Fortunately, heartworms can be prevented with veterinary-prescribed medications that are safe, effective and affordable.

For more information on heartworm prevention and management, visit heartwormsociety.org.

Heartworms pose huge health risks for pets. Fortunately, protecting them from infection is simple.

*****

Photo Credit: (c) EyeEm Mobile GmbH / iStock via Getty Images Plus

About Us

Additional Information

Website & Technical Help

5 Facts Pet Parents Need to Know About Protecting Pets From Heartworms

More News