Finally, finally, the weather is improving, and it’s looking like spring has come to Toronto. While we’re all grateful for the longer days, sunshine and warmer weather, the higher temperatures mean that mosquitos won’t be far behind, and with mosquitos come the risk of heart worm.
What is Heartworm?
Heartworms are long worms, sometimes up to twelve inches long, that live in the heart and vessels that lead to your dog’s lungs. Baby worms called microfilaria circulate in the blood of an infected dog. These baby worms are picked up by a mosquito as it bites your dog and then passed on to the next animal the mosquito bites. Over seven months the microfilaria mature into adult worms living in the dog’s heart and begin to produce another generation of microfilaria. Over time, more and more adult worms take up residence in the dog’s heart, clogging the heart, and damaging the valves, eventually leading to heart failure and death. The good news is that prevention is easy.
Does my dog really need Heartworm Prevention?
Heartworm is spread by mosquitos, so any dog in your area who has contracted heartworm could be infecting your own dog. It is becoming much more common for dogs to travel, spending part of the winter in southern areas like Florida where the infection rate is extremely high. Also, people adopt dogs and bring them home from their winter holidays. Often these rescue dogs have received very little routine veterinary care are carrying heavy worm burdens. Closer to home, there are parts of southern Ontario that have large numbers of reported cases.
In the last six years there have been over 800 cases of heart worm reported in Ontario, and over 2200 in New York State. Toronto always reports a number of cases and some areas such as the shore of Lake Eerie show a high rate of infection. By their very nature, these numbers are on the low side, as they represent only those dog owners who have had their dogs tested. Unfortunately, there are thousands of dogs in southern Ontario that are not tested or on preventative, so the number of potentially infected dogs who could pass the worms to your dog is much higher. Remember: All it takes is one mosquito, biting just one of these infected dogs, then biting yours, to spread a Heartworm infestation to your pet.
To protect your dog, you first have a blood test, after the 15th of April. We are testing for infections from the previous mosquito season. It takes that long for the infection to appear in the blood. Puppies born before the end of mosquito season in Ontario, that is before November 1st, need a blood test. If by chance, they were infected at the end of last fall, letting those worms live in the heart until we test next year could cause serious illness.
Once a dog or pup is found to be negative we put them on a preventative program for the summer. Pups born after November 15th can go straight onto Heartworm preventative this year.
All dogs should start on Heartworm preventative medication by June 1st.