Heartworm Testing for Pets

Heartworms are parasites that live in the heart and can be fatal if not treated quickly.

Heartworm testing is the only way to definitively determine if your pet has a heartworm infection. Examining their stool often won't help you tell if your pet has heartworms. Heartworms are parasites transmitted through the bite of a mosquito. If left untreated it is a potentially life-threatening disease.

How do heartworms affect my pet's health?

Once your pet is bitten by a mosquito, heartworms can complete their life cycle, maturing into adults that mate, reproduce and live in your pet's hearts, lungs and associated blood vessels. More adult heartworms inside your pet can increase the severity of their illness. Dogs are the perfect hosts for heartworms, with their bodies acting as an ideal environment for them to mature and have offspring. If heartworms remain undiagnosed, heartworm disease can lead to heart failure, lung disease, organ disease and in severe cases, it could be lethal.  

How can my pet be tested for heartworms?

We take a sample of your pet's blood to test for heartworm proteins or microfilariae. Adult female heartworms leave protein in your pet's bloodstream, which is detectable with an antigen test. These proteins are only detectable at least 5 months after your pet has been infected with heartworms. The presence of microfilariae means your pet is infected with adult heartworms. These are usually detectable 6 months after your pet was first bitten by the mosquito that transmitted the heartworms. Pets that are 7 months or older should be tested for heartworms. For specific recommendations on when your pet should be tested, please contact us at 416-745-4700.

What are the symptoms of heartworm disease?

Most symptoms manifest during the later stages of the infection, based on the number of heartworms your pet is infected with. Heartworm disease is categorized into 4 stages as symptoms increase gradually, with class 4 being the most severe and class 1 meaning no symptoms or a mild cough. More severe symptoms include:

  • Persistent cough
  • Difficulty breathing
  • Fatigue
  • Weight loss
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