Toronto Veterinarians - Pet Wellness Network

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Contact Willowdale Animal Hospital

Open 24 Hours, Year Round

256 Sheppard Ave. West
Toronto, ON M2N 1N3
(416) 222-5409

Ever wonder what Heartworm is?

Heartworm is a parasitic roundworm (Dirofilaria immitis) that is spread from host to host through the bites of mosquitoes. The heartworm is a type of filaria, a small thread-like worm. The definitive host is the dog but it can also infect cats, wolves, coyotes, foxes and other animals, such as ferrets, sea lions and even, under very rare circumstances, humans. (source: Wikipedia). Think about that the next time you lean down to pet your pooch at the dog park, all the while swatting away those pesky mosquitoes with your other hand. Ah yes… Summer has arrived.

Now that you know what Heartworm is, you may wonder how prevalent it is in your area? Here are some interesting Heartworm facts from a survey done by the University of Guelph:

  • in 2010, 564 dogs were diagnosed with heartworm in Canada (up form 354 in 2002)
  • 76% of these heartworm positive dogs did not travel outside of Canada
  • PEI and Newfoundland & Labrador were the only 2 provinces where no dogs were diagnosed with heartworm in 2010
  • In Ontario 431 dogs were diagnosed with HW in 2010 – 222 of these dogs never left their area. Only 12% of them showed clinical signs.
  • Rescue dogs imported from southern USA states into Canada may have caused an increase in prevalence of heartworn in Ontario Dogs.
  • Heartworm season is from June 1st-November 1st. we recommend contacting your veterinarian to ensure your pet is on an appropriate HW preventive medication.

If you have questions about Heartworm feel free to give us a call. We’ll be happy to answer any of your questions.


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