Understanding Heartworm Disease in Ontario

Heartworm disease is transmitted by mosquitoes and can affect both dogs and cats. While Ontario's climate means the risk varies by season, heartworm prevention should be part of every dog's year-round care plan.

How heartworm spreads

When a mosquito bites an infected animal, it picks up microscopic heartworm larvae. Those larvae can then be passed to the next dog (or cat) that mosquito bites. Over months, the worms grow and live in the heart and lungs, causing serious damage.

Signs of heartworm disease

In early stages, pets may show no symptoms at all. As the disease progresses, you might notice:

• Coughing
• Reduced exercise tolerance
• Weight loss
• Lethargy

Prevention is key

Monthly preventatives are safe, effective, and far less costly than treating established heartworm disease. We typically recommend annual heartworm testing combined with year-round prevention for dogs in our area.

Talk to our team at your next visit — we'll help you choose the right product for your pet's lifestyle.