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Heartworm Prevention in Colorado Dogs and Cats

July 13th, 2015 by Cherished Companions Animal Clinic

In this Colorado pet family, heartworm prevention will be a priority for Bailey, but not Cinnamon.

Have you noticed you’re swatting a lot of mosquitoes this summer?

We have too!

The onset of a heavy mosquito season in Castle Rock means it’s a good time to talk about heartworm prevention in Colorado dogs and cats.

We’ve put together this article to:

  • Share important heartworm prevention tips
  • Answer your heartworm questions
  • Discuss the biggest misconceptions that pet parents have about heartworm in Colorado

(Simply need a heartworm test and meds? Call our veterinarians at 303-688-3858 or book your visit here.)

First things first, what are heartworms?

Heartworms are, in fact, worms.

They’re transmitted to your pet through mosquito bites.

The worms enter your pet’s body as larvae. They migrate through your pet, attaching themselves in your pet’s pulmonary vasculature system (the lung area).

Over six to seven months, the larvae mature into adult worms.

Heartworms can grow so long that they cross your pet’s heart valves and cause heart failure.

They also can cause significant damage to the lungs and arteries.

Are cats at risk for heartworm disease too?

Yes, though, heartworm disease is much less common in cats than in dogs.

Cats are not a primary host, and most worms don’t grow into adult heartworms in cats.

If you’re getting ready to move from Colorado to a part of the country where heartworm is rampant and you’re worried about your cat, our veterinarians are happy to discuss putting your cat on heartworm prevention medicine.

Otherwise, it typically isn’t something you have to worry about for your cat in Castle Rock.

Dogs are at greater risk.

They’re a primary host for heartworm, and they can get infected much easier.

Murray, this Colorado dog, is a primary host for heartworm. Callie, the cat, is not.

What’s one of the biggest misconceptions about heartworm in Colorado?

Some pet parents believe their dogs or cats can’t get heartworm disease because:

  • They don’t expose their pets to other animals or
  • They primarily keep their pets inside

But as we noted above, heartworm isn’t transmitted directly from animal to animal.

Heartworm is carried from one animal to another through mosquitoes.

And there’s no way to know if a mosquito is infected or not.

So, if you let your dog outside (particularly at dusk or dawn) or you ever have mosquitoes in your house, there is a chance for heartworm.

Are dogs at risk for heartworm year round in Colorado or just during the summer and fall?

The risk of heartworm is the highest when mosquitoes are active — typically, summer and fall in Colorado.

Keep in mind, though, mosquitoes can hatch and start feeding any time the temperature rises above 60 degrees.

In Castle Rock, we sometimes have 70-degree days in January!

If you have a dog, it’s a great idea to think about heartworm prevention in Colorado year round.

How common is heartworm in dogs in Castle Rock and Denver?

The good news is that it’s relatively low compared to other parts of Colorado and the country.

At our Castle Rock veterinary clinic, we don’t see too many cases of heartworm.

There tend to be more cases of heartworm in dogs in rural areas, such as around Greeley and Pueblo.

Why do we recommend heartworm prevention in Colorado dogs?

It’s much easier and less expensive for you to prevent heartworm than it is to treat it!

What are some easy heartworm prevention methods?

One of the easiest heartworm prevention methods is a monthly, chewable medication. It kills the immature larvae that are migrating through your dog’s body.

We recommend keeping your dog on heartworm prevention medicine year round.

The companies that make heartworm medicine suggest having your dog tested for heartworm every two years to make sure the medicine is working properly.

If you only give your dog the heartworm prevention medicine during Colorado’s warmest months, we’ll run a heartworm test during your dog’s annual exam.

This will help us make sure he or she didn’t pick up the worm during the off-months.

If you’re looking for additional forms of heartworm prevention, there are topical medications you can apply to your dog as a mosquito repellant.

These topical medications are a good secondary method to decrease the likelihood of heartworm.

However, we don’t recommend using them as the only form of protection.

How does a dog heartworm test work?

You can come into our Castle Rock veterinary clinic for just a dog heartworm test or we can include it in your dog’s annual exam.

In both instances, our veterinary team will draw blood from your dog and run a blood test. We’re looking for indications of the adult worms.

It’s worth noting that it’s possible to get false positives on a dog heartworm test. If your dog initially tests positive, we’ll send your dog’s blood test to a specialty lab for more in-depth analysis.

The sooner you can catch and treat heartworm, the better you can assure that your dog won’t have long-term damage to the heart or lungs!

What are heartworm symptoms in dogs?

If your dog has heartworm, it’s likely that your pup’s heart or lungs aren’t functioning well. As such, you may notice your dog is:

  • Avoiding exercise
  • Coughing
  • Having trouble breathing
  • Just not feeling well

If you see any of these symptoms, it’s time to give our Castle Rock veterinary clinic a call.

Heartworm treatment depends on how severe the disease is. Again, the sooner you take action, the better.

If you’d like to learn more about heartworm in dogs and cats, please check out this info on heartworm basics (from the American Heartworm Society).


Tips from a Castle Rock veterinarian: 8 tips to keep your dog safe & happy in Castle Rock


Cherished Companions Animal Clinic is a veterinary clinic in Castle Rock, Colorado. Specializing in the care of cats and dogs, our goal is to help you and your pet feel more comfortable, keeping your stress to a minimum.

This article is intended to provide general guidance on heartworm prevention in Colorado dogs and cats. If you have specific questions or concerns, please contact your local veterinarian. (If you live in or around Castle Rock, we welcome your call: 303-688-3757.)

© 2015, Cherished Companions Animal Clinic

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