Like the name states, heartworm is a worm that is transmitted by mosquitos and lives in your pet’s circulation system (heart, lungs and blood vessels). Heartworm larvae live in mosquito salivary ducts and are transmitted to your pet when a mosquito bites. The parasites move under your pets’ skin, through the circulatory system and lodges in the arteries of the lungs. As you can imagine, having worms in your blood vessels can cause significant disease. The worms migrate through the circulatory system leading to increased vessel pressure which causes lung disease and eventually ending in congestive heart failure and liver damage.

When is Heartworm Season?

Heartworms require a temperature of 14 degrees to develop and it takes 6 months for the heartworm larvae to mature into adults once established inside your pet. The transmission season in Durham region is May/June to October/November depending on the year and seasonal temperatures. As the climate is warming, we will expect to see heartworm transmission earlier in the spring and later in the fall. If you go further south where temperatures can reach 14 degrees year round, heartworm preventatives are required year-round.

So, what should we do?

It is impossible to protect you and your pets from getting mosquito bites (if there was a way to eliminate the possibility of mosquito bites, I would already know about it as I would be doing it myself!). The only way to protect your pet against heartworm is to use prescription monthly preventative medications from June 1 to November 1. The more pets in the community that are on preventative medications, the less mosquitos will become infected which reduces the chances of transmission. There are some communities in Ontario that do not use preventative medications and have alarmingly high percentages of pets infected with heartworm. I personally helped at wellness clinics in Caledonia, which is 2 hours from Oshawa, where 5 out of 10 dogs that came into the clinic were infected with this life-threatening parasite.

In order to start a preventative program, we must test your pet to make sure they are not already infected with the parasite (or a different medication would be needed to treat the infection). If your test result comes back negative (meaning no heartworm) there is a 99.9% chance that your pet truly does not have heartworm. The test we use at Taunton Road Animal Hospital also checks for tick-borne diseases like Lyme disease, ehrlichia and anaplasma at the same time.

Your pet’s health is in our best interest. Please do not hesitate to call us if you would like to discuss your pet’s heartworm risk, medications available or any questions you have!

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