Our dogs are counting on us to know the facts about heartworm disease.
There are many myths and misconceptions about heartworm disease in dogs. And social media platforms help fan the flames of misunderstanding. As an integrative veterinarian, I have comforted grieving clients who have lost their dogs to this preventable disease and I have read recent information about the growing use of home remedies in place of FDA-approved heartworm preventative. That’s why I want to help you help your dog by sharing the facts about heartworm disease. If you have concerns about heartworm disease in dogs, let’s bust these myths together.
MYTH #1: Heartworms do not exist. Veterinarians and drug companies made them up.
A heartworm picture is worth a 1000 words. These heartworm pictures of a dog’s heart and lungs post-mortem aren’t easy to look at, but they clearly show that heartworms exist. You can see the mass of heartworms in and around the dog’s heart. These are foot long heartworms that lived in the heart, the lungs, and the associated blood vessels. Left untreated, heartworms can live from five to seven years in dogs. And dogs can get several hundred worms in that amount of time.
MYTH #2: I don’t need to give a heartworm preventative to my dog during the winter months because it’s cold outside.
Cold temperatures do not safeguard dogs from heartworm disease and the insects that carry it. I’ve seen many sad cases of dogs who have tested positive for heartworms. The dogs’ owners stopped giving preventative during the cooler half of the year—the winter months. Some species of mosquitoes are adapting to colder climates. Heartworm disease exists year-round in the host animal—such as a coyote, fox, wolf, or an infected dog. It is really important to give heartworm preventative year around. The American Heartworm Society has a slogan:
THINK 12. Protect your pet from heartworm 12 months a year. Test for heartworm every 12 months.Click To TweetPlease help spread the word.
MYTH #3: We don’t have heartworm disease in our state.
This is a very common misconception. All 50 states (and worldwide) have documented cases of heartworm disease in dogs. Not only has it been recorded, but it is also on the rise. Here is a true story that illustrates why this is the case: A client came to me with a dog that needed to be treated for heartworm. The dog and owner had moved into the area about three years prior. Not only was I sad for the dog, but I was also sad because that dog, during those three years, had served as a “reservoir of infection” for the area. That means that if a mosquito bit the infected dog, then that mosquito would then become infected and potentially infect other dogs. It is a domino effect.
Secondly, the convenience and ease of travel in today’s world fans the spread of heartworm disease. After hurricane Katrina, for example, over a quarter of a million pets, many of whom were heartworm positive, were shipped around the country in this great concerted rescue effort. As encouraging and uplifting as this was, it also guaranteed the increase of heartworm incidents around the country.
MYTH #4: My dog is an indoor dog so I don’t need to give a heartworm preventative.
Unfortunately, mosquitoes know no man-made boundaries. Whether it is a house or a fenced in yard, mosquitoes can fly and they’re also blown by the winds, so certainly, they can travel the country. They can get indoors and bite unprotected dogs inside the house. Even an indoor dog who rarely goes outside for more than a walk or potty break is still at risk for heartworms. There are up to 30 different species of mosquitoes that transmit heartworms and they can all slip into a house quite easily.
MYTH #5: My dog’s fecal test is negative so heartworm testing is not necessary.
Many other species of worms (hookworms, roundworms, and tapeworms, for example) are internal parasites that live in the intestines, in the gastrointestinal tract. Heartworms live in the circulatory system—the lungs, the heart, and the associated blood vessels. And because they are found in the heart and the circulatory system (not the intestine), a blood test is needed to detect their presence. Veterinarians administer a separate test (not a fecal test) where they draw a few drops of blood from the dog. Often the lab test results are available in just 10 minutes.

MYTH #6: A home remedy will protect a dog from heartworm disease.
Essential oils. Lemon juice. Vinegar. Coconut oil. There is no home remedy that a dog owner can mix in any form that will prevent a dog from getting heartworms. While I have a healthy respect for some home remedies when used appropriately (and certainly, it is very important that you use the right ones with caution and wisdom), they are not an appropriate treatment for heartworm disease. (And since I’ve mentioned essential oils, if they are in your consideration set for your dog in any way, it is crucial to do your research. Certain brands of essential oils are dangerous for dogs. There are a few that are safe, but they need to be used judiciously. In all cases, they are not an appropriate treatment for heartworm disease.) Please administer FDA-approved heartworm preventative monthly for your dog.
MYTH #7: A dog’s thick fur will protect him or her from heartworms.
“My dog has a really thick coat. There’s no way the mosquito can bite through it.” It is a common misconception that a dog’s thick fur protects him or her from getting heartworm disease. The truth is that mosquitoes bite pets where the hair is thinnest. Often the hair, even in a thick-coated dog, is still thin on the legs or the belly. And that’s where the mosquito is going to bite. I have personally treated heartworm positive Pomeranians, huskies, and other breeds that are known for their thick undercoats. It’s not a protection. Mosquitoes will find the dog’s soft inner groin, belly, and skin where the coat is thinnest.
MYTH #8: Heartworm pills are toxic to dogs.
I understand the concern about what we are putting into our bodies and our dogs’ bodies. But I always tell my clients that with everything in life we have to weigh the benefits versus the risks. I will go on record here that there are certainly many safe FDA heartworm preventatives on the market. I personally give my dogs Heart Guard Plus. It has been around for a long time. And there are other good heartworm preventatives available. My dogs get a monthly heartworm preventative and I’d never open them up for the risk of contracting heartworm disease.
MYTH #9: My dog’s on a flea and tick preventative, so heartworms are covered.
Currently, there is no universal medication for flea, tick, and heartworm prevention in the United States. If you live in the U.S. and you are giving your dog a flea and tick preventative and you believe it prevents heartworms, please speak with your veterinarian. Make sure you are giving your dog monthly heartworm preventative faithfully. There’s no room for error, so if you have questions, I encourage you to have a conversation with your vet.
MYTH #10: It’s ok to go without a heartworm preventative. I’ll treat the dog if he ever gets heartworms.
Treatment for heartworms is both expensive for the dog owner and very painful for a dog. An arsenic-based injection is used to treat heartworm disease in dogs. It is not benign stuff. This is a hardcore treatment for a canine companion. It has to be injected deep in the dog’s muscle. This is painful. The dog must be confined and kept quiet because, as the worms die, they could cause clots in the bloodstream—a life-threatening issue. To help mitigate this risk, the dog is kept very still for months during the course of treatment. (Obviously, this is a challenge in and of itself.) Finally, treating a dog who has heartworms is expensive. Typically, treatment is done through multiple injections. Also, additional medications and diagnostic tests are needed as the heartworm disease can cause other permanent changes in the dog’s body. These changes are irreversible and impact the dog’s quality of life.
Let’s bust these myths together.
If you see these myths about heartworm disease in dogs being propagated in social media, please help set the record straight. Ultimately, dogs are the ones who suffer when we get this wrong. The benefits of a heartworm preventative outweigh the risks. If you are interested in more information, I encourage you to check out my companion podcast episode, 10 Heartbreaking Heartworm Myths, or visit the American Heartworm Society’s website.
What questions or concerns do you have about heartworm disease in dogs? Please comment below.
I was reading research into heartworms and from what I understand the heartworms are developing resistance to heartgard and proheart and the only thing capable of keeping the beagles (poor little beagles) heartworm free was ProHeart 12 shots so why are they still selling them if they’re not working and the worms are developing resistance to them? Isn’t this to use a human term because I don’t know what to call it in veterinary medicine but malpractice! I mean by giving dogs medication that’s starting to not work then if you are one of the lucky ones that get the resistant worms your dog gets to die or you get to pay a ton of money and get accused of not giving your dog the medication properly even if you did! It seems like a waste to buy them considering the low rates of efficiency! But don’t those shots have some nasty side effects especially on some dogs? My dog is a 15yr old Rhodesian ridgeback and I don’t live in an area with high rates of heartworm there, were 3 cases last year reported. Of course that doesn’t mean that is every dog with heartworm because there’s no way to tell whose not treating or testing until they become extremely ill! But when I get a new puppy I would like to know what you’d do with your dog? Continue with the safer yet less effective treatment since I don’t live in the area where they have high rates of infection or play it safe with the heartworms and less safe with the treatments?
Hi Deborah,
I hope I can shed some light on this situation. Evidence shows that some heartworms in certain areas of the country are developing resistance to heartworm prevention. There may be a hereditary component to this resistance passed on genetically in dogs. At this time there is still much we don’t really know. What we do know is that the resistant heartworms are not a widespread concern and year-round heart worm prevention is still the recommendation of the American Heartworm Society. The resistant heartworms are resistant to all preventatives in the macrocyclic lactone family, this includes every heartworm prevention I am currently aware of. Odds are, if your pup comes into contact with heartworms, it will be worms that are not resistant and should be killed easily by any of the current prevention options. I will always keep my dogs on monthly prevention not only to prevent heartworm infection but also to deworm them for intestinal parasites that can be contagious to people. The saying is true, an ounce of prevention is worth a pound of cure. Also, I recommend testing for heartworms yearly. With yearly testing, should an issue with efficacy arise, you can catch the issue quickly and address it. I hope you find the answers you are looking for and can make a decision you are comfortable with moving forward. Best wishes!
So what would be the best home remedy to apply to your 10 year old dog to treat heartworms??? Please I need some assistance in this matter my dog is lethargic and the ribs swole please help
Allen,
Sorry to heart that your dog was diagnosed with heartworm disease and is not doing well. I feel strongly that there are no acceptable home remedies for heartworm disease. Please contact your veterinarian promptly to discuss your dog’s case. Untreated heartworm disease can cause long-term heart and lung damage or even death so it is critical that your dog is treated by a veterinarian using drugs that are developed and approved for that purpose.
Thank you for informative info concerning heartworm! It now has become a problem even in Colorado! I do however have a precaution & that is the shot given for a six month period. My dog was 10 when I began heartworm as it had not been an issue before! I questioned 2 different vets( my dog is not in a private vet practice) about the shot for a dog over 7 yrs old as I had read not a good idea. Both told me it was fine & there was no problem! I was not given an information sheet about the shot to sign & on 2nd visit I agreed to it! Horrible mistake! My dog suffered a stroke or seizure could not eat or drink( I was spooning water in her mouth)! When I did some research I found many dogs much younger had died from same shot & found out from FDA that shot had been taken off market in 2004 put back on in 2014 w/ no change! Shocking! My dog did survive w/ a lot of treatment & care but her face is lopsided she eats & drinks out of side of her mouth as her tongue is crooked& it aged her! I stringy recommend no dog of any age get this shot! Be a good pet owner & give the pill once a month not a big deal, I wish I had a agreed to that not the SHOT!
Hi Debra, You are absolutely right that Colorado is now a state that needs to take heartworm prevention seriously. I’m so sorry to hear your dog’s story, and I’m glad she is still with us. Thank you for sharing your experience. I have to confess that I’m also not a fan of the injection. My concern is that if there is some sort of adverse reaction, there’s no way to get the medication “out” of the body. It’s designed to be a long-acting treatment. However, I do know many colleagues who like and recommend it.