Spring is in the air which means longer days, warmer weather, flowers and Easter bunnies!One other thing this means is that heartworm season is here. Many pet owners are already aware of heartworm and what it is; however, I always find a refresher is excellent, so I’ve put together some information on heartworm in a question and answer format!

What is Heartworm? Who can get it?

As the name implies, it’s a parasitic worm, Dirofilaria immitis, that lives in the heart. It affects dogs primarily; however, cats may become infected as well on rare occasions. The good news though is that humans don’t get it, so we are safe! We are starting to see more and more cases of it in Canada, with the bulk of these cases coming from southern Ontario, so right where we live! And it’s not just outdoor dogs who are catching it, any dog, regardless of lifestyle, can find it, even those who barely step foot outside their apartment! If a mosquito can reach the dog, so can heartworm!

What are some of the common symptoms of a heartworm infection?

Initially, there is very little regarding clinical signs and infection may go unnoticed. Over time as the worms grow and take up more space in the heart and lungs, we may see a cough start to develop. Eventually, you may notice what we call exercise intolerance, where affected animals will get winded easily and not show the stamina that they once had. If not properly treated, this disease is very serious and potentially fatal! Many of the signs mimic other conditions we commonly see, such as heart disease.
Because of this, there is often an extensive workup, including a physical exam, X-rays, and bloodwork. There is a heartworm test that is available as well which will be run and can detect the presence of adult heartworms. If this test comes up confident other confirmatory tests may be run, to help confirm a diagnosis.

My dog is confirmed heartworm positive, what can be done?

Treatment does exist for heartworm! If your dog is not showing any symptoms, or only minor ones, surgery is often not problematic. For those dogs that are showing more severe symptoms, it can be challenging and complications may arise. Regardless of what symptoms are teaching and how big of a worm burden treatment requires several injections and oral medications given over the course of several months. During this time it is also important that exercise is restricted as otherwise a potentially fatal embolism may develop as adult worms die, break up and possibly block pulmonary vessels.

This sounds like a severe disease with a rigorous and prolonged treatment protocol. Is there anything can I do to prevent my dog getting infected?

Why yes there is! Every summer we can put our dogs on what we call heartworm prevention. There are a variety of different products available either as a chew or a local spot on. These are given monthly throughout the summer starting the beginning of June. It’s important to get your dog tested for heartworm before providing any prevention as the prevention may kill the early stage larva which is released by adults in large number leading to a severe inflammatory response. A side benefit to this test is that it looks for several other tick-borne diseases as well, such as Lyme disease. Once confirmed heartworm adverse prevention could be given monthly. Some people travelling down to the states in the winter may want to consider keeping their dog on heartworm year-round as their warmer climate means mosquitoes (and therefor heartworm) is an issue throughout the year.

Written by Dr. David Baker