Ask a Vet with Dr. Sam: Can cats get heartworm?

I heard that April is Heartworm Awareness Month. Can cats get heartworm?

Yes, though heartworm is much more common in dogs, cats can get heartworm too. How do they get it? A cat must be bitten by an infected mosquito in order to become infected with heartworms – heartworms are not transmitted directly from one cat to another or from a dog directly to a cat. Infected cats serve as hosts for other mosquitos, who ingest immature heartworm larvae when they bite an infected cat. The larvae mature for 10-30 days in the mosquito’s gut then move to its mouth. When an infected mosquito bites a cat, it injects infective larvae into the cat. Two host animals are required to complete the complex life cycle of a heartworm!

The larvae migrate into the cat’s bloodstream and end up in the right side of the heart and the pulmonary arteries. They mature into adult heartworms capable of reproduction within six to seven months. About eight months after infection, they begin to produce larvae that will live in the cat’s blood for about one month (during which time, they can infect mosquitoes). 

Are you thinking what I’m thinking? “This sounds bad, what do I do to prevent heartworm in my cat?” This is a great question to discuss with your veterinarian. Feline heartworm disease is challenging to diagnose because there are no specific clinical signs and there is no drug approved for treating heartworms in cats. Heartworm disease is serious and the best treatment right now is prevention (you can get a prescription for a heartworm preventative from your veterinarian). Many cat owners are surprised to learn that indoor cats need to be protected too – it’s estimated that approximately 1/3 of infected cats live indoors only!

For more information on heartworm, talk to your pet’s veterinarian, check out the FDA’s website, or visit the American Heartworm Society’s website.

Do you have a question for the vet? We want to hear it! Email questions to steph@mrfrs.org.