Heartworm disease is transmitted to cats and dogs by a bite from a mosquito carrying the microscopic heartworm larvae. Heartworms are a parasite known as dirofilaria immitis. They have the appearance of thin spaghetti when they reach adulthood. While both cats and dogs can become infected with heartworm, it is far more prevalent among canines. Cats represent only 10-15 percent of the heartworm cases in the U.S.

Undetected and untreated, adult heartworms will infect the arteries of the heart and lungs. It is an extremely serious condition and can lead to heart failure in your pet. Heartworms are more common in hot and humid areas where mosquito infestations are heavy. The average annual number of canine heartworm cases is highest in the southeast region of the United States. Nevertheless, dogs and cats are at risk for heartworm in every state.

Fast Facts about Heartworm

• Heartworm disease is four times more common in dogs than in cats.

• Pets can’t catch heartworm disease from each other. Only the bite from an infected mosquito can transmit the parasite to your pet.

• Wild animals that can acquire heartworms include the wolf, fox, coyote, muskrat, raccoon and ferret.

• The first documented mention of heartworm disease in dogs appeared in the 1847 Western Journal of Medicine.

• It takes seven months for the heartworm larvae transmitted by the mosquito to mature into adult heartworms in a dog.

• Heartworm disease is a silent killer in its early stages. Your pet could be infected with heartworm for months before you would notice any symptoms. That is another reason why preventative medications are the best option for managing this disease.

Preventing Heartworm

Because treatment of advanced heartworm is risky and difficult in dogs and non-existent in cats, prevention is the best protection you can provide for your pets. Chewable heartworm pills are available in either daily or monthly doses.

Top brands include Heartgard and Tri-Heart Plus. Many pet owners opt for topical medications, which are applied directly to the animal’s skin on a monthly basis. These drugs also help manage fleas, hookworms, mites and roundworms, in addition to controlling heartworms. The most commonly used topical medications include Revolution and Advantage Multi. You should ask your veterinarian or pet health center professional which treatment is the best for your cat or dog.

There is also a low dose injection available (Proheart 6) that protects dogs against heartworms for up to six months. It is less commonly used and has exhibited undesirable side effects in some pets. As with any medication, your veterinarian should provide you with the best recommendations for a preventative medicine.

Preventative heartworm medications may cost $50 to $120 on an annual basis for your pet, but that is considerably less than the cost to treat advanced heartworm in a dog ($200-$1,000) or the heartbreak of not being able to treat an infected cat at all.