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As the name suggests, heartworms (or Dirofilaria immitis) settle and live in your pet’s heart, particularly dogs. How to prevent your dog from becoming a heartworm reservoir? What to do if your companion is already affected? Here are some tips from the veterinarians at Passionimo…

How do pets get infected by heartworms?

Mosquitoes transmit this disease to canines. Though rare in Quebec, heartworm disease is very serious. In hotter climate, the vast majority of dogs not treated preventively will be affected. Affected dogs become another potential source of transmission through mosquito bites.

Wild animals, like wolves and coyotes, are referred to as natural heartworm “reservoirs”—reservoirs that are constantly active because left untreated. Mosquitoes get the parasites from those reservoir animals.

More cases occur in municipalities surrounding Aboriginal reserves in south-east Canada, probably due to wild canids acting as reservoirs. Quebec and Ontario are the provinces most affected by heartworms, particularly the Niagara Peninsula. To that end, IDDEX Laboratories developed an online index where you can see the number of reported cases.

Don’t think that dogs who stay mostly indoors are not at risk of mosquito bites. Mosquitoes are everywhere and are vectors of this disease. Preventative measures must be taken for pets travelling South, even if it’s just for a few days.

Can cats also be affected?

Though cats are not natural hosts for this disease; unfortunately, they can also be infected. Cases of cat infections are rare in Canada, but more common in the south-east of the United States.

Although rare, chances of survival for affected cats are virtually zero. They often die from the disease or its treatments. The American Heartworm Society provides recommendations every year, based on the latest statistics.

What are the symptoms of heartworm disease?

This is where things get complicated! Canine filariosis is an insidious and complex disease. Once transmitted by a mosquito in the microfilaria form (the microscopic pre-larva of the adult heartworm), the worm will take 6 to 7 months before reaching its mature stage. It will migrate towards the heart through tissues.

You will not notice the signs right away. Your dog will experience coughing, reluctance to physical exercise, and general loss of health.

A larger number of worms will also have a more significant impact: one worm will not cause the same damage as a dozen of long spaghettis. Additionally, because worms can live 5 to 7 years, your dog will represent a danger for all dogs in your neighbourhood.

Significant time may pass before the disease is detected in dogs, and the diagnosis often comes too late, once the worms have been comfortably settled in the heart for a long time. Many cases are diagnosed during routine tests, leaving owners in shock, never expecting such a serious disease with a very expensive treatment.

How to prevent heartworm infection?

If your furry companion is diagnosed with heartworm disease, the treatment involves several steps. Heartworms cause various diseases, which are often serious and hard to treat, including heart conditions.

That’s why prevention plays such a key role. Preventing heartworms is so easy; there’s no need to hesitate. Your veterinarian will recommend the best preventative treatment. Prevention medication is efficient and safe to use for most dogs.

It’s easily administered once a month by feeding your dog special kibbles, for instance. In addition, nowadays, the same medication can prevent and treat fleas, the common summer parasites, and intestinal parasites.

Should prevention be done every year?

Yes, and generally, we recommend conducting a screening test before administering prevention medication. It should however be pointed out that it takes at least 6 months before an infection can be detected in the animal’s blood.

This is why many veterinarians will recommend a screening test every year or every two years, depending on your pet’s history. If your puppy was born after mosquito season the previous year, no screening is necessary. A screening test consists in a blood draw for a subsequent analysis.

Another benefit of the screening test is the opportunity to check for more common diseases such as ehrlichiosis, Lyme disease, and anaplasmosis. It’s suspected that climate change and the migration of some bird species contributed to the outbreak of those rare diseases in Quebec. The saddest part of this is that anaplasmosis and Lyme disease also affect humans and can cause long-term sequelae.

When is the ideal time to begin administering prevention medication?

Because the high-risk season ends in late November, it’s preferable to conduct the screening test in April or May and to begin prevention medication on June 1st. It’s IMPERATIVE to administer the last dose in November, which corresponds to the end of mosquito season.

The risk of infection is greater in the late season. If you pet gets sadly infected, this last dose could protect them. Otherwise, the parasite will have 6 months to grow and reach the mature stage in the heart of your companion.

Remember that your veterinarian can help you to prevent, diagnose, and treat heartworm disease. For more information, please contact the nearest Passionimo veterinary clinic.