Mosquitoes don't discriminate, and on a warm New Hampshire evening they'll bite whatever's nearby, including your dog or cat. That single bite is all it takes to pass along heartworm disease, a condition that can seriously damage your pet's heart and lungs if left unchecked.
The reassuring part is that keeping your pet safe from heartworm is straightforward, affordable, and backed by decades of veterinary research. Below, our team at Animal Care Clinic Monadnock walks through what heartworm disease actually is, the prevention products available, and how to build a protection plan that fits your household.
Here's what we'll cover:
What heartworm prevention actually does for dogs
Whether cats need protection too
The different prevention formats on the market
Why year-round dosing matters, even in New Hampshire winters
How safe these medications really are
Not Just a Dog Problem: Heartworm and Cats
Many pet owners assume heartworm is strictly a canine issue. That's a myth worth clearing up right away. Any mosquito bite carries risk, so both cats and dogs need a prevention strategy tailored to them.
The culprit is a parasite called Dirofilaria immitis. Once a mosquito passes it along through a bite, the worms travel through the bloodstream and settle into the heart, lungs, and surrounding vessels. From there, they multiply and cause damage that can range from mild to catastrophic.
This isn't a disease limited to humid southern states. Cases have been documented in every U.S. state, including here in New Hampshire, where warmer, wetter summers have made mosquito season longer than many residents realize. Cats tend to show fewer obvious symptoms than dogs, which can make heartworm harder to catch early, and unfortunately there's no approved heartworm treatment for cats once they're infected. That makes prevention the only real safeguard for our feline patients.
The American Heartworm Society maintains detailed, regularly updated guidance for pet owners, and it's worth a look if you want to understand the bigger picture of risk and prevention.
Choosing a Prevention Method That Fits Your Pet
There's no single "best" heartworm product. The right choice depends on your pet's temperament, your budget, and how easily you can stick to a schedule. Here's a rundown of the main categories.
1. Monthly Chewable Tablets
These flavored chews are a favorite among dog owners because they're easy to give and often doubling as treats. Most are dosed monthly and also guard against common intestinal parasites like roundworm and hookworm, which are worth watching for in a region with plenty of wooded trails and wildlife.
2. Topical Monthly Applications
Applied directly to the skin, these are a solid alternative for pets that won't tolerate pills, and they're frequently used for cats. Many topical products bundle in flea protection as well, which is handy during the buggier stretches of a New Hampshire summer.
3. Long-Acting Injectable (Dogs Only)
Given by a veterinarian, this option can protect a dog for six months to a full year depending on the formulation. It's a good fit for owners who travel often or simply want one less monthly task to remember.
Do New Hampshire Pets Really Need Year-Round Coverage?
Yes, without question. Even though our winters bring plenty of snow and ice, that doesn't mean mosquito risk disappears entirely. Consider these points:
Mosquitoes can shelter indoors, in barns, sheds, and other sheltered spots, and a string of mild winter days can bring them back out earlier than expected
Gaps in dosing weaken protection: These medications rely on a consistent, uninterrupted schedule, and pausing between seasons undermines their effectiveness
National veterinary organizations agree: The American Heartworm Society, the Companion Animal Parasite Council, and the American Veterinary Medical Association all recommend year-round prevention rather than a seasonal on-and-off approach
Our team at Animal Care Clinic Monadnock sees this play out locally every spring, when owners who skipped winter doses discover their pet needs retesting before restarting prevention. Staying consistent saves you that extra step.
How Safe Are These Products, Really?
No medication is entirely without risk, but FDA-approved heartworm preventatives have been studied extensively and have strong safety track records. Side effects are uncommon, and when they occur, they're typically mild.
Correct dosing matters more than people sometimes realize. Products are formulated by weight range, so always check the label matches your pet's size rather than assuming one product fits all pets equally. If you're ever uncertain about a specific medication, a dosing schedule, or whether it's time to switch formats, that's exactly the kind of question our veterinarians are happy to answer.
The Bottom Line for Local Pet Owners
Heartworm disease is serious, potentially fatal, and entirely preventable with the right approach. Between the mosquito activity we see across the region during warmer months and the way pests can linger indoors through milder winters, New Hampshire pets face real exposure risk throughout the year.
Annual heartworm testing paired with consistent monthly or scheduled prevention gives your pet the strongest defense available. If it's been a while since your last visit, reach out to Animal Care Clinic Monadnock and let's put together a plan that works for your dog or cat's specific needs.
Frequently Asked Questions
Do indoor-only cats in Peterborough still need heartworm prevention?
Yes. Mosquitoes regularly find their way indoors through open doors, screens, or gaps in windows, so indoor cats in Peterborough and the surrounding area still face exposure risk and benefit from monthly protection.
Which heartworm prevention option costs the least?
Monthly oral chewables are generally the most budget-friendly choice, though exact pricing depends on your pet's weight and the specific brand your veterinarian recommends.
Is a heartworm injection better than a monthly pill?
Both are effective when used as directed. The injection offers longer-lasting convenience, while monthly pills give owners more flexibility to adjust or pause under veterinary guidance.
Can I purchase heartworm prevention without visiting a vet first?
Most reputable products require a prescription along with a recent negative heartworm test, and we don't recommend unproven home remedies like garlic or essential oils, since there's no scientific evidence they work.
What should I do if I forget to give a dose?
Give the missed dose as soon as you remember and call your veterinary team for guidance, since skipped doses can lower your pet's protection and may require a follow-up test before restarting.
Ready to get your pet's prevention plan on track? Contact the Animal Care Clinic Monadnock team to schedule a wellness exam, heartworm testing, or a parasite prevention consultation. We're here to help keep your Peterborough companion healthy through every New Hampshire season.
Book an Appointment or call us at (603) 924-9033.