Feline Heartworm

Heartworm infection is caused by a parasitic worm called Dirofilaria immitis. Infected mosquitoes carrying heartworm larvae (baby heartworms) transmit the parasite when they bite a cat. The worms make their home in the cat's circulatory system and can cause the animal to become very sick. While percentages vary regionally, the percentage of cats that have heartworm infection in the U.S. ranges from 1-14%.1 A study from North Carolina shows that both indoor and outdoor cats are susceptible, though cats that spend more time outside increase their chances of being bitten by mosquitoes.2

Signs of Possible Infection

Signs of heartworm infection in cats may include coughing, intermittent vomiting that is usually unrelated to eating, lethargy, lack of appetite, weight loss and signs that mimic asthma or allergic bronchitis. Heartworm infection can lead to lung damage, respiratory distress, seizures and even death. Cats often show no signs of infection, so it's important to ask your veterinarian about heartworm testing as part of your cat's annual wellness exam.


The American Heartworm Society Guidelines list specific treatments available for heartworm-infected cats with or without acute signs. They range from treating obvious clinical signs with inflammation-reducing steroids (prednisone) to stabilizing very ill cats with treatments appropriate for shock. According to the circumstances, options include giving fluids, oxygen, keeping cats confined, medications to help them breathe easier, steroids to reduce inflammation, drugs for their heart and lungs, antibiotics and nursing care.

Testing and Prevention

Heartworm infection can be hard to diagnose. It may be necessary to run multiple tests depending on initial findings and signs. There is now an in-clinic test that detects heartworm antigen and allows you to get results within minutes, enabling your vet to discuss prevention and/or management options with you before you leave the clinic. Additionally, x-rays and other diagnostic methods may be used to determine or confirm the stage of infection.

Leading experts such as the American Heartworm Society recommend conducting a blood test to determine if your cat has already been infected. As there hasn't been a highly effective treatment for heartworm infection yet developed, prevention is by far the best method to keep your cat free of infection. Monthly preventive treatment is available through your veterinarian.

1 Miller MW, Atkins CE, Stemme K, et al. Prevalence of exposure to Dirofilaria immitis in cats in multiple areas of the United States. In: Seward RL, ed. Recent Advances in Heartworm Disease: Symposium '98. Proceedings of the American Heartworm Society. p 161-6.

2 KNOW Heartworms Inside & Out, Volume 1. Available at: Accessed July 2007.

Q. I thought heartworm infection was a dog disease. Cats can get heartworm too?

A. Yes, cats are also affected by this parasite. Although heartworm is often considered a canine disease, it turns out that cats are also at equal risk for heartworm infection.

Q. How can I prevent heartworm infection in my cat?

A. There are preventative medications available that are very effective. Most of the preventatives are administered on a monthly basis and are widely available. Talk to your vet to learn more.

Q. Can I get this disease from my pet?

A. No, this disease cannot be transmitted from your pet to you or your family.

View all questions

Thank You

Your email has been sent to your friend