Pet Health Library – Marin Pet Hospital, San Rafael, CA

Heartworm is a preventable, but serious and potentially fatal, parasite

that primarily infects dogs, cats and ferrets. It can also infect a variety
of wild animals, including wild canids (e.g., foxes, wolves, coyotes), wild
felids (e.g. tigers, lions, pumas), raccoons, opossums, and pinnipeds (e.g.,
sea lions and seals), as well as others. There have been documented
human infections, but they are thought to be rare and do not usually
result in signs of illness.

How is heartworm transmitted and what does it cause?

Where are heartworms found?

Geographically, heartworms are a potential threat in every state as
well as in many other countries around the world. All dogs, regardless
of age, sex, or living environment, are susceptible to heartworm
infection. Indoor, as well as outdoor, cats are also at risk for the disease.
If you plan to travel with your dog or cat to a different part of the
country, or another country, ask your veterinarian about the risk of
heartworm infection in the area where you are going to relocate or
visit.