Canada’s Heartworm Fiction and Facts 2021

Owner giving dog Heartworm Prevention medication
Spring is the time of year when veterinary teams focus on educating pet parents about the risks of heartworm disease.  Heartworm disease is a potentially fatal parasitic disease transmitted by mosquitoes.  Adult heartworms live in the large blood vessels of the heart and lungs.  They can obstruct blood flow and cause significant damage to the cardiorespiratory organs and vessels.  Dogs are the preferred hosts for heartworms, but cats, ferrets, and even people can be infected.
 
Signs of heartworm include coughing, fatigue, weight loss, respiratory distress, collapse, and even death.  Many cases of heartworm can be asymptomatic for years, so annual testing is important.
 
Fiction: Heartworm disease can spread from dog to dog.
Fact: Not directly.  Heartworm is spread by the bite of an infected mosquito.  When a mosquito bites an infected dog, they ingest immature heartworms called microfilaria.  After spending 10-14 days inside a mosquito, the microfilaria becomes infectious larvae.  This means that they can now infect the next dog (or other mammals) that the mosquito bites.
 
Fiction: Cats don’t get heartworm disease.
Fact: Cats aren’t the preferred host for heartworms, so they aren’t infected as easily as dogs.  However, when they do become infected, they can experience severe diseases including respiratory distress and sudden death.
 
Fiction: My indoor dog does not need heartworm tests or prevention.
Fact: Most indoor dogs spend some time outdoors and mosquitoes can make their way into the house.  All dogs should be tested for heartworm annually and prevention should be used as recommended by your veterinarian for your area.
 
Fiction: I don’t need heartworm tests or prevention if I live in a cold or dry climate.
Fact: Cold, dry areas with low mosquito populations have a lower incidence of heartworm disease than warm, humid climates.  However, heartworm can still be introduced to an area through the movement of infected pets, wildlife, and climate change.  Furthermore, pets that travel with their owners may be at increased risk for heartworm infection.  Talk to your veterinarian about your pet’s lifestyle and the risk of heartworm in your area.
 
Fiction: Heartworm disease is easily treated.
Fact: There is no safe treatment for heartworm disease in cats.  Heartworm treatment for dogs takes months and it includes risky medication, hospitalization, supportive care, exercise restriction, and sometimes surgery. Even after successful treatment, dogs may experience ongoing illness due to the damage the worms caused. Preventing heartworm is the safest, most economical means of protecting your pet from this parasite.
 
Fiction: My collie, border collie, or Australian shepherd cannot have heartworm preventative medication.
Fact: Although these breeds are more sensitive to some antiparasitic drugs, the low doses used in heartworm prevention are generally safe for collie-type dogs.  
 
Fiction: My cat does not need heartworm prevention.
Fact: Some cats should be given monthly heartworm prevention.  Outdoor cats in endemic areas, like Southern Ontario, do have a risk of contracting heartworm disease.  If your cat spends any time outdoors, ask your veterinarian if heartworm prevention is recommended for your area.
 
Fiction: Over-the-counter or natural remedies can protect my pet from heartworm.  
Fact: Safe and effective heartworm preventatives can only be acquired by prescription from your veterinarian.  There are no licensed over-the-counter products available for heartworm prevention in Canada.  Natural remedies such as essential oils, herbs, and supplements are not effective at preventing heartworm infection, and may not be safe for your pet.  Your veterinarian is the best resource for information about safe, effective heartworm prevention.
 
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Written by:
Dr. Sperry, DVM, Veterinary Advisor, Pets Plus Us
The information provided and contained herein are the opinions of PTZ Insurance Services Ltd. which are based on external publication. The content is not intended to be a substitute for professional veterinary advice. PTZ Insurance Services Ltd. assumes no responsibility or liability for any loss, claims or damages arising out of the within content.