ArcaMax

"Today, we know cats are about as susceptible to heartworm as dogs are," Jones says. Even indoor cats can be bitten by mosquitos, and the American Heartworm Society even recommends protection for them.

It's not a good day for the heartworm that's transmitted into a cat. Heartworms in cats may or may not mature into adults. Still, even immature worms can cause damage. The good news is, infected cats typically harbor only one to a handful of worms. The bad news is, even a single worm can be fatal, and there's no treatment.

Some cats develop heartworm-associated respiratory disease (HARD), which has symptoms similar to feline asthma. While HARD can be treated, the cat remains in periodic and often chronic discomfort, and the treatment isn't cheap.

Feline heartworm is the second most common cause of sudden death in cats (next to feline hypertrophic cardiomyopathy, a common heart disease in cats). Obviously, sudden death can't be treated. And, to date, veterinarians have no technology to predict if this sad outcome will occur.

Some cats with feline heartworm show a variety of severe symptoms, such as blood clots in the lungs and lung inflammation, which can occur when the adult worms die in the cat's body. Some cats have more generalized symptoms, such as vomiting. Some lucky cats with feline heartworm have no symptoms, and live out what seems to be a normal lifespan, finally succumbing to cancer or kidney disease at a ripe old age.

"We now understand that just like dogs, all cats with heartworm suffer some damage, and just live with it," says Jones. "Even when cats' immune systems kill off worms before they develop into adults, there may be permanent damage."

There are tests to detect heartworm in cats but they aren't perfect. For dogs, there's an accurate screening test for heartworm, which dogs should get annually, according to Jones.

"There are dogs on preventives who get heartworm, and we to know that," Jones says. While no drug is perfect, heartworm drugs are incredibly effective; the failure rate is exceedingly low. More commonly, a dog may spit out or throw up oral doses in succession, or owner compliance (forgetting to give the heartworm preventative) is poor. Veterinarians report that occasionally dog owners find a secret stash hidden behind a sofa.

Heartworm preventives should not be confused with the medication required to treat heartworm disease. Using a preventative in a dog with active heartworm disease can cause a severe reaction.

There are a variety of heartworm preventives available for dogs, cats, even ferrets. Many also kill intestinal parasites. One product (called ProHeart 6) offers six months of protection; other products are monthly. See your veterinarian for the right recommendation for your pets.

Learn more from the American Heartworm Society: www.heartwormsociety.org.

========

(c) 2015 DISTRIBUTED BY TRIBUNE MEDIA SERVICES, INC.