FAQs About Heartworm in Pets

Heartworm disease is a serious disease caused by a parasitic worm called Dirofilaria immitis and spread through the bite of a mosquito.

In the United States, heartworm disease is most common along the Atlantic and Gulf coasts, and along the Mississippi River, but has been reported in dogs in all 50 states.

Here are a few frequently asked questions about heartworm along with answers.

Q: First Off: What is Heartworm?

A: Heartworm is an internal parasite that can infect animals, including cats and dogs.

Q: Is Heartworm Dangerous?

A: Yes. Heartworm can result in severe lung disease, other organ damage, heart failure and even death in dogs and cats.

Q: How Does Heartworm Infection Occur?

A: The worms live inside a mosquito for a short transition period in order to become infective and able to cause heartworm disease. When a mosquito carrying the disease bites an animal, the mosquito transmits miniscule heartworm larvae into the animal’s bloodstream. From there, they make their way to the heart, lungs and surrounding blood vessels.

Q: How Big is an Adult Heartworm?

A: Heartworm males can reach about 4-6 inches in length and females up to 12 inches in length, and can survive 5 to 7 years in dogs and up to 3 years in cats.

Q: How Does the Cycle of Infection Continue?

A: Adults living inside an infected animal mate and give live birth to larvae. These larvae enter that animal’s bloodstream. When a mosquito bites this animal, larvae are transmitted to the mosquito. This mosquito can start the cycle again by biting the next animal.

Q: What are the Signs of Heartworm Disease?

A: Signs and symptoms vary. If the infection is light, there may be no signs or mild symptoms such as an occasional cough and tiredness after moderate activity. Common signs of heavy infection include weight loss, poor haircoat, exercise intolerance, coughing, fever, trouble breathing and signs of heart failure.

Q: Can You Test for Heartworm?

A: Yes. The heartworm test requires just a small blood sample from your pet and your veterinarian will recommend a further testing if they think it’s necessary.

Q: Is Heartworm a Problem Year-round?

A: Contrary to what owners may think, the American Heartworm Society’s recommendation is to use heartworm all-year-round, no matter what the season, and have your pet tested every 12 months!

Q: What are the High-risk Areas in the United States?

A: The five states with the highest incidence of heartworm are Mississippi, Louisiana, South Carolina, Arkansas, and Alabama.

Q: What Should I Do to Keep My Dog Safe from Heartworm?

A: The best heartworm treatment is year-round prevention! Talk to your veterinarian to decide which preventive is best for your pet. It’s easier, less expensive and much less stressful to prevent heartworm disease in dogs than it is to cure it.

Q: Can Heartworm Disease be Cured?

A: Treatment is available, but can be costly. For safety reasons, it’s vital to confirm diagnosis before proceeding with treatment. During and after treatment dogs should rest and not exercise for a period of time, as directed by your veterinarian.

Q: Is Heartworm Disease Contagious?

A: No. Heartworm disease is not contagious and is only spread through the bite of a mosquito. A dog cannot catch the disease from being near an infected dog.

Q: Can Cats Become Infected with Heartworms?

A: Yes. Heartworm disease in cats is a bit different than in dogs, and cats are not as susceptible to infection as dogs. The average lifespan of heartworms in cats is only 2 to 4 years, whereas in dogs it is 5 to 7 years. Signs include coughing, asthma-like attacks, vomiting, lack of appetite and weight loss. Some cats even struggle to walk, faint or have seizures. Cats with heartworm disease rarely show signs of heart failure, but rather respiratory signs that are the most obvious due to the lung damage caused by the heartworms. Again, prevention is the best treatment! Talk to your veterinarian to decide which preventive is best for your cat.