Heartworm disease poses a significant threat to pet well-being. While heartworms are found in all U.S. states and an estimated 1 million pets are infected, risks are highest for pets in the southern and coastal areas where mosquitoes thrive. Pet owners who understand heartworm disease have the crucial knowledge and the tools to protect their furry pals from this devastating—but preventable—illness. To assist pet owners on their journey to heartworm enlightenment, the Southern Crossing Animal Hospital team answers frequently asked client questions.

Question: What are heartworms?

Answer: Heartworms are parasitic worms that reside in the heart, lungs, and blood vessels of infected pets and wildlife. Infected cats host only one to six worms, but infected dogs can host 30 to 100 or more of the foot-long worms. In an infected pet, heartworms can damage local tissues and eventually lead to heart or respiratory failure.

Q: Are heartworms contagious?

A: Heartworms are not contagious from pet to pet, but the risk of contracting heartworms rises with each infected pet in the community. This is because heartworms are transmitted through the bite of infected mosquitoes, who pick up the heartworm larvae (i.e., microfilariae) from other infected pets or wildlife. The more pets who have circulating larvae in their bloodstream, the riskier the situation for neighboring dogs and cats.

Q: My pet stays mostly indoors. Are they at risk for contracting heartworms?

A: Since heartworm is transmitted by mosquitoes, which frequently enter buildings and homes, all pets are at risk for heartworm infection. Dogs and wild canids are the primary and preferred hosts, but cats, ferrets, and some other mammals can also pick up the disease. Outdoor pets are at increased risk, especially if they aren’t on a prevention medication.

Q: What are heartworm disease signs in dogs and cats?

A: Most infected dogs show no obvious disease signs right away. After the initial infection, the heartworms take several months to grow into adults, and then more time to reproduce and cause damage that could lead to signs, which in dogs may include coughing, fatigue, decreased appetite, or weight loss. Infected cats are often asymptomatic, but they can also develop severe respiratory disease or sudden death, which occurs when the cat’s immune system overreacts to the worms’ presence. 

Q: How is heartworm disease in pets diagnosed?

A: Heartworm disease is diagnosed through blood tests that detect worm antigens or microfilariae in the bloodstream. Screening tests are recommended annually for dogs, or more frequently for pets at high risk or whose preventive treatment has lapsed. A heartworm test does not show positive right away, which means some infections are missed initially, but likely will be detected the following year. Testing for cats is unreliable and difficult to interpret, so is not recommended unless the disease is suspected. 

Q: What is the treatment for heartworm disease?

A: Treatment for heartworm disease in dogs is a multi-step process, because standard dewormers don’t affect adult heartworms. Treatment typically includes two or three injections to kill adult worms, antibiotics and steroids to prevent adverse reactions to the dying worms, and strict cage rest to avoid stressing the heart or lungs. Surgical removal may be required in severe cases in dogs with a high worm burden or in cats with significant and intractable disease, because no other treatment options exist for cats.

Q: Can I prevent heartworm disease in my pet?

A: Prevention is the ideal way to protect pets from heartworm disease. Key preventive measures include administering monthly heartworm prevention medication as recommended by our veterinary team and minimizing your pet’s exposure to mosquitoes. Heartworm prevention is safe and cost-effective compared with risky, painful, and costly heartworm treatments. Ask our team for recommendations for products, which are available in topical, oral, and injectable formulations, that will work best for you and your furry pal.

Heartworms are prevalent in our state and region, putting all pets—including indoor cats—at risk for contracting the disease. The Southern Crossing Animal Hospital team recommends all pet owners provide routine prevention medications and follow species-specific testing protocols for diagnostic screenings. Contact us to schedule your pet’s next routine visit and heartworm test, or to learn more about the impact of heartworm disease on our community.