If you’re running low on your pet’s heartworm preventative, you might be wondering if it’s okay to skip a few months over the winter. The truth is, no matter where you live, you should protect your pets against heartworm all year.

It’s a widely circulated myth that pets can only contract heartworm disease in the summertime. While heartworm infections are more prevalent in warmer weather, it’s possible for pets to get infected in the winter.

How Do Pets Get Heartworm Disease?
Heartworm is spread from animal to animal via mosquitoes. As a mosquito feeds off an infected animal, they take in microfilariae, tiny baby heartworms that circulate through the bloodstream. Inside the mosquito, the microfilariae mature into larvae, which it then transmits to another animal.

Since mosquitoes are the only vectors of heartworm, veterinary professionals once believed that it was safe to forgo preventives in the winter months, when mosquitoes are scarce. Now we know that some species of mosquito do not die off by wintertime. Instead, they may hibernate and temporarily become active on an unseasonably warm day.

Also, keep in mind that while mosquitoes are not normally active when it’s 50 degrees Fahrenheit or cooler outside, they can remain active indoors. It’s not uncommon for homes with a water leakage or other damp indoor environment to become a breeding ground for mosquitoes at any time of year. This is also why indoor-only cats need heartworm preventative too.

What’s more, staying on a year-round monthly schedule makes it easy to remember to give your pets heartworm preventatives on time. You can even travel with your pet to a warm destination in the winter without having to worry about their exposure to heartworm.

What If I Skipped Heartworm Preventative This Past Winter?
If your pet has been off heartworm preventative for a few months, you’ll need to see your veterinarian before restarting.

When a pet becomes infected with heartworm larvae, they will not show signs of infection right away. It will take about 45 days for the larvae to mature into juvenile adults. If the pet takes a heartworm preventative before that period, the medication will kill the larvae before they mature.

If a pet has an active heartworm infection, and they are given a preventative, at best, the preventative will not be effective on adult heartworms and they will still be infected. At worst, the medication may kill microfilariae in the blood so rapidly that the pet can actually have an anaphylactic reaction and possibly die.

That’s why your veterinarian tests your pet for heartworm every year, and why it’s so important to have your pet re-tested if you have skipped more than one dose.

It takes six months for a pet to test positive for heartworm, so your pet will need to be re-tested if there is a chance they have been exposed.

More Reasons To Give Heartworm Medication Year-Round
Monthly heartworm preventatives like Heartgard Plus not only protect your pet from heartworm disease, but also protect them against other common parasites that they can pick up at the park, like roundworm and hookworm. Trifexis even protects your pets against fleas, and Simparica Trio covers fleas, ricks, and heartworms!

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