top of page


Heartworm in dogs

Heartworms are parasitic roundworms that infect dogs, wild canines and other animals like cats and ferrets.

They’re spread via mosquito bite and infect the heart and lungs. Heartworm can be fatal for dogs as well as cats and even ferrets. Cases of heartworm have been found all across the continental U.S. and southern Canada, so if you suspect your dog may be infected, it’s important to bring him or her in for a heartworm test at our Toronto clinic.


Most heartworm treatments focus on prevention. Measures should be taken year-round, to counter exposure that may have occurred over the last few months — the life cycle from infection to maturity for the parasites can be as long as seven months! There are two main methods for heartworm prevention in Canada: pill or topical treatment. Some medications target only heartworm, while others double as prevention for other parasites. It’s important to talk to your vet about the best option for your dog.


In the latent period, before the larvae have embedded themselves and begun to mature, heartworm is difficult to detect. Dogs will usually have no symptoms but the infestation will show on testing before symptoms occur. Yearly blood testing is recommended to catch it early so it can be treated. Once symptoms start showing, it’s almost always too late to treat. Once the infestation is well established, early symptoms typically include cough and shortness of breath. Occasionally, blindness and other conditions can arise if the heartworms have infected another part of the body. In such a case, testing is required to determine if the problem is heartworm.


Damage from heartworms can be serious and might involve multiple organs. It’s important for the veterinarian to check the health of your dog’s organs before deciding on a treatment. A lot of tests will be required, including X-rays and blood work, to determine how serious the infection is. Treatment usually involves the injection of medications to kill the heartworms. Treating it involves multiple visits to the vet and during the treatment period, it’s important that your dog stays calm when recovering at home. This is because the breaking up of the heartworms can cause a blockage in the pulmonary vessels, and it’s dangerous if the dog’s heart rate gets too high.


If you’d like to talk to someone about preventive heartworm medication for your pet, or if your dog requires a heartworm test, contact us at Bellamy-Lawrence Animal Hospital today. We offer a full range of prevention, testing and treatment options in Toronto to keep your dog healthy and safe.

bottom of page