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Fact vs. Fiction: The Truth About Heartworms

Updated: Jul 1, 2022

One bite from a mosquito; that's all it takes for heartworm disease to grow and spread. The process is simple: Mosquito bites an infected dog and the heartworm larvae grow into infective larvae. Then the mosquito bites an uninfected dog and leaves them the most unwelcome, unwanted present: the larvae. The larvae continue to grow and travel through the dog's blood for the next six months until their journey ends in the dog's fragile heart and they mature into adults. Those adult heartworms can then grow up to 14 inches long and survive for up to seven years, destroying the dog's organs in the process.

Horrific, right? Yet so many dogs of Gulf County experience this life-threatening disease. Part of this is because of misinformation from "old wives' tales" about heartworm, so this month, we want to address some common misconceptions about heartworms and how they actually spread.

Myth 1: Heartworms are contagious and can even be passed through water bowls.

The only way for heartworms to spread is through a mosquito bite. The larvae needs to incubate in a mosquito to become infective. Heartworms are never passed from an infected animal directly to another animal through contact or shared food and water bowls, nor does an animal get them from drinking bad water. It always comes down to a mosquito bite.

Myth 2: Heartworms aren't a problem for indoor pets.

Since we've established mosquitos are the sole way heartworms are spread, let's ask ourselves, has a mosquito ever made it inside your house before? Yeah, exactly. Your pet may not venture outside much but they don't need to, since mosquitos are all too willing to come to them and you never know which mosquito is carrying infective larvae. So even indoor pets need regular heartworm preventatives to stay safe.


Myth 3: Heartworm disease is only a issue.

As great as it would be to say this is the case, sadly, mosquitos can hatch and begin their biting sprees even in 40-degree weather. It's best to give your pets year-round protection against heartworms and mosquitos since it only takes a single mosquito to infect your pet with heartworms, and that mosquito may hatch at any time.

Myth 4: Natural remedies work just as well as preventatives.

While drug-free strategies like eliminating standing water (which is a breeding ground for mosquitos) and natural insecticides and repellants may help reduce the likelihood of your pet being bit by a mosquito - and thus potentially infected with heartworms - it's vital to remember a few things. For one, these should be used only in addition to FDA-approved heartworm preventatives, not in place of them, because as great as anecdotal evidence may seem (your Aunt Beth may swear by those garlic cloves), the effectiveness has not been proved by science like heartworm preventatives have been.

Additionally, just because something is okay for you does not automatically mean it is safe for your pet to have it on their skin or to ingest. For instance, garlic can be toxic for dogs, since too much garlic easily causes them to develop anemia as well as stomach upset. Point being, please always consult with your veterinarian before giving your pet a supplement. Aunt Beth means well but may not always know best.

Myth 5: Monthly preventatives are costly and hard to administer.

The cost comparison between monthly preventatives and treating a dog with heartworms is easily showcased by our Healing Hearts campaign for dogs with heartworm disease. Basically, treating a dog with adult heartworms can cost hundreds to thousands of dollars, and it may still be too late for them if their organs have been too damaged by the worms. On the other hand, giving your pet monthly preventative costs about the same as buying a pizza. Isn't it worth giving up that one pizza a month to treat your pet with something that can save you hundreds of dollars, and most of all, save their lives?

On top of that, heartworm preventatives are available in a variety of forms. Have a pup that loves treats? Give them a chewable pill to sneak in with the next hot dog. Can't imagine forcing your pet to take a pill? Try the spot-on treatments that are available. Do you mean well but keep forgetting to give your dog heartworm preventative? Talk to your vet and opt for the twice-annual injection instead. There is a way for every pet owner with any kind of pet to ensure their four-legged friend gets the preventative measures they need to survive and thrive.

Let's each do our part to help prevent heartworm disease, especially as temps warm up into full-blown mosquito season. And if you're in a position to help dogs that are battling this horrible disease, please consider giving to our Healing Hearts fund. Our goal is to raise $20,000 to cover the cost of treating shelter dogs infected with heartworms this year alone. We give all the dogs under our care monthly preventatives but around 80% of the dogs that come to the shelter in the first place already have adult heartworms that require costly treatment. Please help us heal the hearts of these dogs so they can go on to their happily-furever-afters.

Pet insurance is a great option in addition to monthly preventatives. Heartworm treatment is expensive and pet insurance could help give you piece of mind everyday knowing your pet is protected! Visit for more information.

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