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Can Cats Get Heartworms From Fleas?

Dr. Mark is a veterinarian with over 40 years of experience in the field. He works with dogs, cats, exotics, and livestock.

Fleas are a pain for cats, but they do not cause heartworm.

Fleas are a pain for cats, but they do not cause heartworm.

Even though heartworms are spread by blood, and fleas drink blood, they are not able to spread heartworms. (1) The heartworm parasite (Dirofilaria immitis) is only able to develop in the body of a mosquito and is only transmissible via mosquito bites.

If you want to prevent infection, the most important thing is to keep your cat inside to reduce the risk of he or she being bitten by mosquitoes. If you live in an area where heartworms are endemic, the best thing to do is keep your cat on heartworm preventative.

In general, cats are not as susceptible to heartworms as dogs, as the worms do not thrive the same way in cats. (2)


  1. American Heartworm Society. 2022. Heartworm in Cats.
  2. US Food and Drug Administration. 2019. Keep the Worms Out of Your Pet’s Heart! The Facts about Heartworm Disease.

This article is not meant to substitute for diagnosis, prognosis, treatment, prescription, or formal and individualized advice from your veterinarian. Animals exhibiting signs and symptoms of distress should be seen by a veterinarian immediately.

© 2022 Mark dos Anjos DVM