Why I Practice Heartworm Prevention in my Cat

By June 2, 2018 Uncategorized

by Dr. Ashna Varma BVM&S MRCVS

HEARTWORM. You hear about it every year from your veterinarian come summer, and follow through the very important motions of a blood test to ensure your pet is negative, and responsibly start monthly prevention…if you own a dog.

Heartworm disease is sadly overlooked in cats. It has proven to be serious and potentially fatal, with no approved treatments available for cats specifically (There is an approved protocol for heartworm treatment in dogs). Remember, heartworm disease is a mosquito-transmitted blood parasite that carries a high mortality rate. Most cats in North America are indoors, this is true, but I can guarantee you’ve ended up with a mosquito bite at some point within the comfort of your home. When it comes to caring for my own cat, that possibility is enough to cause concern.

For a long time, heartworm disease in cats was unheard of, as it is difficult to diagnose in cats particularly. It usually requires a post-mortem to definitively prove, but most of the time these deaths usually look like any other feline respiratory or heart failures, such as chronic asthma and allergic bronchitis. Because of this, feline heartworm disease is grossly underrepresented.

Cats are not the classic heartworm hosts compared to dogs, thus most worms do not actually survive to reach their adult state, however when they do, cats will typically have 1-8 worms, whereas dogs can have 30+. Nonetheless, if cats are in a Heartworm endemic area, they are most certainly at risk for contracting the parasite.


Symptoms mimic that of many other respiratory & cardiac diseases in cats, including but not limited to

  • Coughing or asthma-like breathing changes
  • Vomiting
  • Collapse or seizures
  • Abdominal fluid accumulation

When heartworms die in the body, they can trigger anaphylactic reactions or artery blockages that cause the above symptoms and death.


Again, as with dogs AND cats, HEARTWORM PREVENTION is the best way to prevent infection and possibly fatal illness and death. For cats, safe monthly heartworm prevention products are available from your veterinarian.

As a reality check for the ‘elusive heartworm disease’ that we rarely see in the GTA due to the high compliance rate of prevention use (thank you pet parents!!), I work with a Wellness clinic in Ohsweken, Ontario each year. We continue to see positive Heartworm dogs, although less year to year, as more owners begin prevention, and more dogs are treated. Positive heartworm dogs continue to be a source of infection to heartworm negative dogs & cats. Heartworm disease is very real, and very scary.


Dedicated to my special kitty, Moshi, an indoor girl who is a clever avid hunter in my backyard on her harness and leash. I want her to live the longest, fullest, healthiest life, and no mosquito is going to change that! She is on a monthly heartworm preventive from June to November every year, and every 3 months between November and June.

Please visit the following website for more information on feline heartworm disease:


Dr. Ashna Varma BVM&S MRCVS



  1. https://www.heartwormsociety.org/

Purina ProClub Cat Update Volume 14, winter 2016

Leave a Reply