We have had 1 Heartworm Positive dog here at Ajax North Pet Hospital! 

What is heartworm you ask? 

Heartworm is a worm that is passed on to dogs and cats when a mosquito bites them. In the USA an average of 7 in 10 mosquitoes in a heartworm-positive dog’s kennel carry heartworm. The risk is significantly higher in the USA BUT it is still found in Canada, and Ontario.

In addition to heartworm, Lyme Disease has shown a large increase in North America over the last few years. Lyme disease is transmitted by a type of tick called the “Black Legged” or “Deer” tick. Ticks, as well as fleas, can be found anywhere, but especially in wooded outdoor areas. The symptoms are fever, loss of appetite, reduced energy and difficulty moving. 

 We have had one positive test so far this year, but looking at http://www.petdiseasereport.com/content/prevmap.aspx?currentprev=LS we can see there have already been 8 positive test in Ontario this year! Unfortunately this map only shows the reported cases, therefore the numbers can be even higher than they appear. 


Heartworm can be fatal and the treatment for a heartworm positive dog is very extensive and financially straining. There is no treatment for cats with heartworm. 

For a dog who is tested positive it takes at least 271 days to complete the first treatment. As soon as a dog is diagnosed, all physical activity must be restricted. That means cage rest and no walks. The dog has to be on a leash just to go to the back yard for bathroom breaks. This requirement might be difficult to adhere to, especially if your dog is accustomed to being active. The reason it must be restricted is because physical exertion increases the rate at which the heartworms cause damage in the heart and lungs. 

So what’s the solution to this problem? 

Heartworm and Lyme Preventative medication and testing! 

It is important to test your pet for heartworm and lyme before you begin preventative medication as a heartworm or lyme positive dog can lead to serious illness or even death. 

Here at Ajax North Pet Hospital we use Revolution. Revolution is an easy, safer, and effective way to prevent Heartworms. 

It also protects your dog and cat from; Fleas -Ear mites- Mange mites- 2 species of ticks (Rhipiceohalus Sanguineus and Dermacentor Variabilis) and each application provides a deworming for Roundworms and hookworms.  Revolution is a prescription drug called Selamectin, it is NOT a pesticide. It is safe in pregnant and lactating females as well as kittens and puppies over 6 weeks of age and older. 

For more information on Heartworm or Revolution OR to book an appointment please contact us

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