Heartworm disease is a serious and potentially fatal disease in pets in the United States and many other parts of the world. It is caused by foot-long worms (heartworms) that live in the heart, lungs, and associated blood vessels of affected pets, causing severe lung disease, heart failure, and damage to other organs in the body. Heartworm disease affects dogs, cats, and ferrets, but heartworms also live in other mammal species, including wolves, coyotes, foxes, sea lions, and—in rare instances—humans.

All dogs should be tested annually for heartworm infection, and this can usually be done during a routine visit for preventive care.

Heartworm infection in cats is harder to detect than in dogs because cats are much less likely than dogs to have adult heartworms. The preferred method for screening cats includes the use of both an antigen and an antibody test (the “antibody” test detects exposure to heartworm larvae). Your veterinarian may also use X-rays or ultrasounds to look for heartworm infection. Cats should be tested before being put on prevention and re-tested (as the veterinarian deems appropriate) to document continued exposure and risk. Because there is no approved treatment for heartworm infection in cats, prevention is critical.