Heartworm Q & A

We’ve compiled a list of common questions and answers about heartworms for new and seasoned pet owners.

What is a heartworm?

It’s exactly how it sounds: a worm that lives in the heart! These parasites inhabit primarily dogs and cats.

How does my pet get Heartworm?

Mosquitoes! These pests are a nuisance to us and our furry companion, but they also transmit illnesses, like Heartworm disease. This is why “Heartworm season” in Southern Ontario starts in the spring and goes throughout the summer. That’s when we see mosquitoes.

Why should I test my pet for Heartworm?

Pets rarely show symptoms of Heartworm disease until the infection is large and has already caused irreversible damage. While Heartworm preventatives are effective, they are not a treatment. It is important to ensure that the doses are given on time and for the full heartworm season, and sometimes doses are missed. Testing is done to ensure your pet does not have Heartworm disease. Testing gives assurance that our pets are safe.

How do we prevent Heartworm?

There are oral tablets given by mouth, or topical solutions that are prescribed to prevent Heartworm. These preventatives for your pet are meant to be used once a month. Ask us which might be most appropriate for your best friend.

If everyone uses preventative, doesn’t that mean the risk is low?

While we are lucky to have many wonderful clients who want to prevent these infections, the threat remains in Ontario. The primary carriers are canines that don’t have a loving owner: coyotes. The same coyotes you see roaming the parks, trails or behind your home are the ones being bitten by the same mosquitoes that can later bite your dog.

How can I protect my pet if I don’t use preventative?

Ask your veterinarian to perform heartworm tests annually. This way, any infection your pet may get will be in the early stages and therefore easier to treat.



Dog thinking about ticks and fleas

Year-round protection means more peace of mind!

“Tick season” used to mean spring/summer/fall, with a break over the winter – the colder weather meant that we could take a break from worrying about these pesky bugs and the diseases they can transmit. But in the last few years, we’ve seen a change creeping up on us, with the weather staying warm later into the season, and spring arriving earlier each year – and the bugs are loving it!

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Last updated: November 25, 2022

Dear Clients,

Below are some important updates to our operating policies.


This includes vaccines, wellness exams, blood work, heartworm testing, spays and neuters, dental services, and more!



Have you welcomed a new furry family member to your home? We’d love to meet them! Visit our Must Know New Pet Owner Information page for useful resources and helpful recommendations for new pet owners.

Your dedicated team at Westbridge Veterinary Hospital