Heartworm Prevention

In our climate, heartworm disease is a year-round threat for all dogs and cats in our care. Spread by mosquitoes, heartworms are difficult to treat and potentially deadly. Fortunately, regularly administered heartworm preventives reduce the threat of heartworms to near zero.

What is a Heartworm?

Heartworm disease is caused by a parasitic worm called Dirofilaria immitis. Once transmitted to a pet by a mosquito, heartworms mature into adults, mate and produce offspring while living inside the infected animal. The worms are called “heartworms” because the adults live in the heart, lungs and associated blood vessels.

Heartworm Preventives

Most commonly-used heartworm preventives come in tablet form, with the monthly dosage based on the pet’s body weight.

The preventive works by killing any heartworm larvae that may be present in your pet’s body from a mosquito bite that occurred since you administered the preventive the previous month.  The active ingredients do not stay in your pet’s bloodstream for the 30 days between doses, but the monthly dose prevents any heartworm larvae from reaching adulthood because it takes longer than a month for the larvae to mature.

Preventives do not kill adult heartworms already present.

Required Testing

You can purchase heartworm preventives only by prescription from a veterinarian, and the prescription can be written or renewed only after a blood test to confirm your pet does not have an active infection of heartworms. Pets already infected with heartworms who receive preventive can have severe, life-threatening reactions to the dying, circulating larvae in their bloodstreams. That’s why the doctors at Brownsburg Animal Clinic will not prescribe or renew a prescription for heartworm preventives without a test.

Often, active heartworm infections in animals on preventive happen when the owner forgets a dose or runs out for a month or two. Even clients who faithfully administer the preventive can unknowingly miss a dose if their pet spits out the pill or vomits it up in the yard. Testing at least once a year, or at any time you want to resume using preventives after one or more missed doses, is the best way to minimize risk and provide the best care for your pet.

Year-Round Protection

In our climate, mosquitoes are much more numerous during the spring, summer and fall than in winter, but any time we experience unseasonably warm temperatures, mosquitoes can appear right here in Brownsburg during the winter months, too.

Because of these unpredictable seasonal temperature changes, the American Heartworm Society now recommends year-round prevention in every state. We strongly recommend year-round protection for Brownsburg-area pets, too.

As an added benefit, some heartworm preventives help control other parasites, such as fleas, mites, ticks, roundworms, hookworms and whipworms. Talk to your veterinarian about the available options and guidance in selecting the best product for your pet.