Matters of the heart: Why heartworm prevention is so important

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Provided photo

Dr. Anna Dunton-Gallagher

On Valentine’s day we think about hearts, flowers and chocolate (and love, of course.) The trouble is that I just don’t love chocolate as much as I love other candy, so except for heart-shaped Peeps this holiday can fall a little flat for me. When I think about hearts I think about heartworm disease. This is probably one of those word associations that would put me into some abnormal category, but those of you who know me likely already put me there. So let’s talk about heartworm facts this Valentine’s Day!

Heartworm disease is spread by mosquitos and is quite literally a worm that lives in your dog’s heart. They then reproduce until the heart is so full of worms that it cannot pump correctly. Thankfully, heartworm disease in Vermont is not as common as other places, but the new influx of southern dogs and warmer winters is helping it become more common. We are now seeing heartworm disease in dogs that have never stepped a paw out of Rutland county.

Why do we test dogs every year for heartworm disease if you give a pill each month? We do trust that you give the heartworm pill every month and that it is working. However, it is possible that they spit it behind the couch or throw up that meal in the yard when you aren’t looking. While these cases are likely few and far between, it is not worth the risk of skipping a test that can reveal if there is a worm living in your pet’s heart. Additionally, many people do not give prevention through the winter. When there is a zero chance of a mosquito biting your dog, a heartworm pill isn’t really even necessary. The risk is that we will end too soon or start too late if we get out of the habit.

Giving heartworm preventative pills year-round is the gold standard. The pills also deworm your pet for other intestinal parasites each month, which is especially important in families with young children. In Vermont, it is almost impossible for a pet to contract heartworm disease in mid-winter. However, our winters are becoming shorter and milder, which means mosquitos are surviving longer and appearing earlier. The most important months to give heartworm prevention are April through November, but this changes with the yearly weather, and all veterinarians will agree that prevention year-round is ideal. If you do take a winter break, make sure the start date is listed on your calendar and that you haven’t forgotten, until the fateful June day that you come in with mosquito welts all over.

Heartworm disease is very detrimental to pets. While having a worm in your heart is just plain awful, I won’t leave it at that and will discuss their importance further. Your pet may have very few signs until the worms get large enough to affect the heart function. However, once the worms do start to affect the heart, many of the changes are not reversible. The structure and function of the heart change, and the lungs can also be affected with these blood-flow changes. If we can detect a positive early on, we can treat the disease early and prevent lasting heart damage.

The heartworm life cycle is complex, but the take-home message is that the test we use reacts positively to female worms of reproductive age. If a dog tested negative last year because they were only infected with the juvenile stage, they may test positive this year if a worm reached adulthood. Dogs that have a high risk of exposure (imported from warmer climates) we recommend testing even sooner than a year. Local dogs testing positive has heightened our concern, and made yearly testing plus monthly prevention even more important.

Giving a heartworm preventative is essential in preventing heartworm. While the pill may seem expensive at first glance, the cost is low compared to the cost of treatment. Treatment is involved and requires that owners keep their pets confined without running or playing for 4-6 weeks afterwards (even the calmest pet starts to go stir crazy after that long!) Treatment involves killing the worms, which means that there are pieces of dead worms traveling throughout their bloodstream. As an owner of two very active dogs, I know that I will gladly shell out some extra money per month to never have to leave my crazies in a crate for six weeks.

Cats can also get heartworm, but so far it is almost unheard of in our northern climate. While we hope it stays this way, most vets also carry a heartworm preventative for cats.

It truly is worth the money to prevent and test for heartworms, a deadly disease that we can avoid easily. After all, few things in life give you their hearts as wholly as our animals and none make a cuter valentine! Let’s do our part to take care of those hearts.

Dr. Anna Dunton-Gallagher

Dr. Anna Dunton-Gallagher is a veterinarian at All Points Animal Care in Rutland. Have a question on this or any animal health topic? E-MAIL:

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