Everything You Need to Know About Heartworm

And how to prevent it

It’s April and that means it’s National Heartworm Awareness Month! In order to get the most accurate information about this disease, I asked Dr. Jennifer Catalina of Goodison Veterinary Center!

Everything You Need to Know About Heartworm
Dr. Jennifer Catalina of Goodison Veterinary Center

I’m so thankful for her because I learn so much each time I get her answers back. Read our other blog about pet obesity here. I had NO idea that heartworm is caused from the bite of a mosquito! It definitely makes me think twice about being more responsible about when I give my pups their preventative, making sure it’s the same time every month. Especially in the summertime!


What is heartworm? What does it do to your dog? How do they get it? How do you know? What are the symptoms?

Heartworm Disease is caused from a worm that enters the bloodstream from the bite of a mosquito. It travels through the blood until it reaches the pulmonary artery (not heart like the name implies). Because the worm can grow very long, up to a foot, it often invades the heart and lungs as well. In early stages of the disease, often times there are very few to no symptoms. Signs can include a cough, lethargy/fatigue, inability or decreased interest to exercise, decreased appetite/weight loss. In later stages, pets develop heart failure; which can be  life-threatening. In this late stage, few dogs survive without medical help (surgical removal of the worms). The mosquito is the main host of the heartworm. The insect is not affected by it, only transmits the worm when it bites someone. The important part of this is that the mosquito has to bite someone already infected to pick up the worm; it then in turn bites someone else, and this is how spread continues.

How do you prevent it?

Unfortunately, closing your windows, and not letting your pets outside does not prevent mosquitoes from getting in. The best way to prevent your pet from getting the disease is to keep a product in his/her system that does not allow the worm to grow (it kills the worm before it can cause harm). However, giving the product every month is important because just like the growing concern for antibiotic resistance, there is growing concern for these worms growing resistance. If given monthly, this decreases the chance of the worm causing harm.

Everything You Need to Know About Heartworm

What brands do you recommend for preventatives? Don’t recommend?

There are many brands available. It is best to talk to your veterinarian about what best suits your pet; some breeds have sensitivities to certain products, some may have allergies to some of the flavored chewable tablet options, etc. Again, monthly coverage is key! Many people are looking to more natural options. Please be cautious as these have not been studied, and have no evidence of preventing disease. Cases have presented with heartworm disease despite holistic efforts. Also keep in mind that the products are very safe. This is in comparison to the treatment if your pet were to become infected. The treatment for heartworm disease is a combination therapy that involves a series of steps; including a chemotherapy agent. This can have side effects. Also, the cost of treatment is far more expensive than monthly prevention.


Where are the best places to purchase these preventatives?



Where shouldn’t you purchase them?

They are prescription drugs and therefore need approved from a licensed veterinarian. If you bought a product over the counter or online without approval, chances are that your are not using the correct product; it may say for worms but there are many other types of worm-disease (intestinal parasites)

Everything You Need to Know About Heartworm

What do you do if your pup has heartworm?

Make sure you go to your veterinarian for testing EVERY YEAR. Remember, there is the possible worm that could have resistance. Even though a product is given once a month, testing should still be done every year to make sure your pet is clear of any chance of disease. The products are designed to kill the worm; if the worm grows large and invades the artery, and then a product is given without proper testing, it can be life-threatening to your pet.


Some states promote seasonal prevention. That is, during winter season prevention can be discontinued. This is very risky. The heartworm does not test positive until it has been in the blood stream for 6-7 months. If your pet gets bitten the month before discontinuing, then the worm has those several months without any product killing it. Furthermore, many products cover more than heartworm disease. Therefore, keeping coverage monthly helps prevent against over parasites such as intestinal parasites or fleas which may not be affected by.

Prevalence of this disease is changing in many wintered-season states. This is due to travel. Many people travel with their pets to warmer states. This puts their pet at risk, especially if not on prevention, for mosquito exposure. If infected, this pet harbors disease; and when he/she returns to their home state they are a candidate for the next mosquito to pick up the worm and become the next insect-host. And this is how the spread continues.

Everything You Need to Know About Heartworm


I hope this post was informative and encourages you to do everything you can to prevent heartworm disease. Comment below if you have any questions for Dr. Catalina that could be answered in our next blog post.

Thanks for reading! P.S. I am putting on Revolution on Trigger in the featured image. 

Xo, The Bark Blogger

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