Why Should I Use Heartworm Prevention?

Heartworms are treatable, right? So what’s the big deal about using heartworm prevention? If my dog gets it, I’ll just have him treated and he’ll be fine.¬†Unfortunately, it’s not quite that simple.

Using heartworm prevention medicine might seem like an unnecessary expense, but it is easier and safer to prevent heartworm disease than it is to treat it.

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Take a look at this very short video of a dog’s heart that is infected with heartworms.


Those long stringy things are the heartworms, and they aren’t supposed to be there. By this time, your dog is feeling very sick. The heartworms are getting in the way of his heart doing it’s job. Your dog isn’t getting enough blood flow to his lungs, liver, or kidneys. His major organs aren’t working their best, and that makes toxins build up in his blood and he just plain doesn’t feel good. His lungs aren’t getting enough blood, so he is probably coughing, having a little trouble breathing when he’s laying still, and having a lot of trouble exercising.

Sure, heartworms are treatable. But let’s talk about how they are treated. A drug called immiticide is injected into your dog’s veins. Immiticide will kill the heartworms. When the heartworms are alive, they stay in your dog’s heart. Once they die, they sort of “fall out” of the heart. Sometimes the dead worms stay inside the heart in the chambers, but sometimes they float away and out into your dog’s blood vessels. Wherever they go, now your dog’s body has to break down the dead worms. This causes a big reaction with lots of inflammation. While the drug that is used to treat heartworms is not usually harmful to dogs, this reaction to the dead worms can be very dangerous.

If the dead heartworms float out of the heart and into the rest of your dog’s body, they can get stuck in a blood vessel. This can cut off blood supply to part of a vital organ (like the liver or kidneys) and cause serious damage. The dead worms can get stuck in your dog’s lungs, and cause serious damage there. Depending on where the worms get stuck, this can be a life-threatening situation for your dog.

Wherever the dead heartworms end up, there is a very big inflammatory reaction. This reaction can cause a lot of swelling and fluid build up in the area around the worms. Depending on where the reaction is and how severe it is (it is different in every dog), this can be life-threatening for your pet.

Giving heartworm prevention once a month (if you’re using the pills or a topical medicine – every 6 months if you’re using the shot) means that the teenage heartworms get killed before they have a chance to grow up to adult heartworms and cause these problems. It means that the chances of your dog getting sick from heartworm disease is very, very low. The medicines in heartworm prevention are very safe for your pet and cause no inflammatory reaction like the treatment does. (The teenage heartworms are microscopic, and don’t cause a reaction when they die.)

Using heartworm prevention might seem like an unnecessary expense, but it is worth every penny. Heartworm prevention medicines are less expensive than treatment for heartworm disease. Heartworm disease itself can be life-threatening, and treating your dog for heartworm disease can also be life-threatening.

Is your dog on heartworm prevention medicine? Call us or come in to talk about getting your dog tested for heartworm disease and to start him on heartworm prevention medicine.

Check out our Heartworm Disease Resource Page for even more information about heartworms.

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