Heartworm Disease: What You Need to Know to Protect Your Pets


National Heartworm Awareness Month is coming up in just a few days during the month of April. Heartworm disease is one of those topics that you have probably heard at least something about by now. But before you conclude you already know about heartworm disease and prevention, take a moment to read on just to be sure you’ve got all the important facts. And then, pass the information along – because this is a topic every pet owner needs to understand.

Heartworm disease is certainly an expansive topic. There is even a society solely devoted to heartworm disease – The American Heartworm Society (and yes, they have tons of great resources so check out their website!). Our ‘Paws to Protect: Heartworm DIsease’ tab also provides you with essential heartworm disease information. So today, instead of getting into extensive details about the disease, we decided to pull together some critical points we want all owners to understand. At the end of this blog you will find a list of other resources that you can explore if you are interested in more detailed information.

Did you know?

  1. Dogs and cats are susceptible to heartworms. Did you know that recent studies have shown cats can be infected with heartworms nearly as often as dogs? The disease course in cats differs from the disease course in dogs. While cats can develop the “classic” disease caused by the adult worms, they can also develop something called heartworm-associated respiratory disease (HARD) caused by the dying larval or juvenile worms.
  2. Heartworms are transmitted by mosquitoes. Of course, we don’t need to point out that mosquitoes can get inside houses…
  3. The heartworm lifecycle is a bit complicated, and it takes about 6 months for the cycle to complete. Once a mosquito infects a dog or cat with the heartworm larvae, the larvae continue to grow and develop in the animal over the next 6 months or so. Monthly heartworm prevention is only effective against certain early developmental stages of the heartworm larvae. Once the larvae get past a certain growth stage, the prevention can no longer kill the larvae. This is why it is so important not to miss a dose of heartworm prevention!
  4. Speaking of missed doses of heartworm prevention, it doesn’t just happen because an owner forgets to give the dose. Some pets will walk away and spit the pill out.  Others might vomit the pill before it was fully absorbed. For topical heartworm products, if the product is applied incorrectly, or washed away before absorption, the dose will be ineffective.
  5. ​Another variation of a pet missing a heartworm dose could be due to under-dosing. Did your pet gain weight? That could mean they need a different strength of heartworm prevention.
  6. Year-round heartworm prevention is best for all dogs and cats – whether they live indoors only or spend time outdoors. It is impossible to predict when mosquito season will begin or end, and some mosquito species will overwinter indoors.
  7. A heartworm infection can cause irreversible changes in the pet’s body. While there is a treatment available to kill adult heartworms in dogs, the treatment is hard on the body and does not come without risk. For cats, there are no approved treatments to kill adult heartworms. 
  8. When you give heartworm prevention to your pet, you are very likely also giving your pet protection against other parasites. Check your product label – you might be surprised to see all the other things you are protecting against!
  9. Treating a heartworm infection is more expensive than buying the heartworm prevention!
  10. Most importantly, preventing the disease means your pet never has to experience the problems that come from a heartworm infection. That sounds like the best reason of all!

Interested in learning more? Check out these resources:

Author: Dr. C. Noureddine, DVM, MS

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