Heartworm FAQs

When is heartworm testing performed?
Heartworm testing in Canada is between April 15th and June 1st. In Canada, we have the advantage of our cold winters (they have to be good for something!) to help keep the spread of heartworm confined to a certain period

Why do you only test during this period?
Heartworm disease is transmitted through an infected mosquitoes’ bite to your dog. The parasite takes six months to show up on a blood test. If your dog was infected last mosquito season with a parasite, we want to make sure we are testing six months after to catch any infection from the previous season.

I’ve seen mosquitos in May. Why do we start heartworm prevention on June 1st?
For a mosquito to be a carrier of heartworm, they need first to bite an infected animal. That mosquito needs roughly three weeks of temperatures of 14C (60f) degrees or above to incubate the heartworm and be a carrier able to infect your dog. Also, the heartworm prevention that we recommend works retroactively, so if you apply it on June 1st, it will cover your pet from May 1st.

My dog has a pre-existing condition. Will this medication interfere with their illness/current medication?
Most heartworm, flea or tick preventions are safe to use with pre-existing conditions and other medications. Your pets health care team will be sure to take your pet’s whole history into account. It will ensure there are no contraindications with any medications or illnesses specific to your pet.

Why should I have Annual Wellness Testing done on my pet?
Just as your doctor will recommend for you, we recommend yearly blood testing for your pet. Testing allows for early detection of disease as well as creating a baseline so that we know what the normal values are for your pet. These values could be extremely helpful if they were ever to get sick. Early detection of disease can help us to begin treatment promptly, which can assist in your pet living a longer more enjoyable life.

My pet is healthy — why do I need Wellness Testing?
It has been shown that around 10% of pets with no clinical signs (meaning they appear healthy to the owner and veterinarian upon physical exam) have an underlying medical condition. Animals are very good at hiding symptoms — they cannot speak to tell us how they are feeling, and many chronic diseases have no early warning signs. Yearly Wellness Testing is an excellent tool for uncovering these things. Remember too that pets age more rapidly than we do so, the progression of diseases tend to be much more rapid.

Can my cat contract heartworm disease?
Yes — unfortunately, accurate testing in cats can be difficult and expensive. If there are no indications of infection (coughing or panting) the technician or veterinarian may recommend putting your cat on preventative medicine to help protect them. As with dogs, this prevention is applied monthly.

I am a new client who only wants a heartworm test and/or prevention. Can I get these things without an examination?
No — heartworm prevention is by prescription in Canada. In order to prescribe this medicine to your pet, according to our regulations, we need to have a doctor/client relationship. One of our doctors needs to perform a physical examination. After this exam, we would be happy to take a heartworm test and get your pet the prevention they need. It also applies to Wellness Testing if we have never seen your pet before our doctors cannot interpret the blood results without first performing a physical examination.

Why do I need prevention into November?
Our weather can be tricky, and in Ontario, we are known to have warm periods of weather even in late October. Giving the last dose on November 1st ensures that your pet is protected even when we have infected mosquitos late in the year.

Why doesn’t my puppy need a heartworm test if they are less than six months of age?
They were not alive during heartworm season last year, so there was no opportunity to become infected. We will put them on heartworm prevention for this season and then they will begin their annual testing protocol next year. This means puppies born after October 31st do NOT require a test.

Written by: West Hill Animal Clinic