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Medically Reviewed by Veterinarian Angela Dwywer, DVM on April 29, 2018
Table of Contents
I wandered out into my yard this morning to find crocuses poking their pretty little heads up around the base of the tree where I planted them – glorious little bursts of color that tell me spring is finally here! Of course that means that summer is on its way, and with it, heartworm season. That, in turn, led me to think about heartworm prevention for dogs, and the misery that can result when people who live in areas where heartworm is prevalent fail to get heartworm protection for their dogs.
My friend Anna is one person who experienced the agony of losing a beloved pet to heartworm. Anna and I met in college, way back when I thought I was going to do something with my life other than freelance writing and dog blogging. She was your typical “artsy,” always wandering around in maxi dresses and gum rubber boots, contemplating the universe, creating bizarre paintings, and playing jazz piano like a beast. Her life path led her to New Orleans, which I’m given to understand is pretty much the jazz capital of the world, and is now apparently leading a really happy life playing in smoky bars. We still keep in touch on Facebook and via email.
Okay, you know I’m always telling you stories, and you’re probably wondering when I’d get to the point of this one. I won’t keep you in suspense any longer. To make a long story at least a bit shorter, about a year ago Anna adopted an adorable little Red Bone Coonhound puppy. She immediately took him to the vet for his initial checkup and shots, but…
And here I don’t know if Anna didn’t realize that Louisiana is number 2 in the top ten states for heartworm, or if she had an inept veterinarian who didn’t have the sense to tell her about the need for heartworm prevention for dogs in an area where one out of every 26 heartworm tests will come back positive. Anna’s puppy was not tested for heartworm, and received no protection. By the time Anna realized that something was horribly wrong – it began with coughing and proceeded to lethargy – it was too late. Her puppy collapsed and died on the way to the vet. He was just nine months old.
Anna is still grieving, and wondering if there was something she should have done. I’m not giving her a hard time over it, because she didn’t know about heartworm. But you can bet that anyone who does know, and doesn’t get heartworm protection for their dogs, will not be cut any slack by me. Heartworm is deadly, but very preventable.
With that in mind, let’s look at some of the most common questions that can be asked and answered about heartworm.
How Does a Dog Get Heartworm?
There is only one thing that can cause heartworm. It’s carried by mosquitos, and when a mosquito that is carrying heartworm larvae bites your dog, your dog can be infected. It doesn’t require repeated exposure, either – just a single bite from a single mosquito that is carrying the larvae can transmit heartworm to your dog.
For this reason, it’s vital that you get heartworm protection for your dogs. You could begin by purchasing an outdoor mosquito trap, and for sure that will go a long way to protecting your dog from these horrid flying pests, but it’s not enough. Even the best trap will probably only get most, but not all, of the mosquitos. Your dog should still get veterinary heartworm protection.
Keep in mind, too, that although some states are hotbeds for heartworm, all 50 states have mosquitos, and all it takes is one bite.
You live in Arizona. Good for you. I know that Arizona is typically a dry state, but mosquitos can still thrive in areas that are irrigated. Mosquitos exist practically anywhere that you can find water. If you have water, and mosquitos, and dogs, it quite simply adds up to the potential for heartworm, and remember – it only takes one.
But I Live in Oregon! Nevada! California! Aren’t Those Safe Areas?
Again, great. All these states used to be relatively free of heartworm, and veterinarians would even tell owners not to worry about heartworm prevention for their dogs, because the likelihood of contracting heartworm was so low. If your veterinarian isn’t up to speed, he or she might even still believe that this is the case.
My point here is that regardless of where you live, you should still think very seriously about heartworm protection for your dogs. I don’t want you to end up like Anna, grieving and asking yourself over and over if you messed up.
How Long Does it Take for Heartworm to Develop?
From the point where the dog is bitten to the point where the symptoms become obvious, it takes roughly 7 months. At this stage, the worms will begin to invade not just the heart, but the lungs and the blood vessels – and then they’ll breed like crazy, and grow like crazy. An adult heartworm can grow up to a foot in length and live for about seven years. A dog that has a heartworm infestation could have up to 250 worms in his body.
Is Heartworm Transferable to Humans?
You can’t get heartworm from your dog – it’s non-transferable. You could conceivably end up with a heartworm infestation if you’re bitten by a mosquito that’s carrying the larvae, but usually humans are not infected. A heartworm larva might find its way into your body, but it won’t usually live. Humans are far less vulnerable to heartworm infestations than are their canine companions.
So, heartworm protection for humans is probably overkill, if it’s even available. Heartworm protection for dogs, though, is essential.
Is Heartworm Transferable to Other Dogs?
Again, it’s not transferable. A dog can’t get heartworm from another dog.
I’ve Heard That Animal Shelters are Hotbeds for Heartworm. Is That True?
Yes, it is. Animal shelters are also hotbeds for other deadly conditions, like canine parvovirus (for more on this, see my post, Pyometra – The Uterine Infection That Can Kill Your Dog). When you adopt a dog from an animal shelter, you always have to be alert to the possibility that you will be adopting an ill animal. Most shelters simply don’t have the financial resources to ensure good health in the dogs they offer for adoption, so you could very well end up with a puppy or adult dog that has heartworm.
That doesn’t mean that you shouldn’t adopt from a shelter. It just means that you will have to commit to treating any illnesses that your new friend might have. Not getting treatment isn’t an option, and treatment isn’t all that costly. In fact, heartworm prevention for dogs will cost you less in the run of a month than if you had a cup of coffee at Starbucks once a week. A full year’s supply of heartworm prevention for dogs won’t cost you any more than $80, and could be as low as $35.
What Should I Do if I Think My Dog Has Heartworms?
First, look for the symptoms. In the early stages, there won’t be any. But as the worms invade the heart, most of the time, your dog will begin to cough and become lethargic. When the infestation is severe, your dog might retain fluids, or pass out because his brain isn’t getting enough blood. Finally, if left untreated, heartworms will kill your dog.
What if I Didn’t Get Heartworm Protection for My Dogs?
When an owner doesn’t get heartworm protection for their dogs, and the disease has progressed, treatment is still possible but expensive. The dog will need a workup before being treated, and this will include bloodwork and x-rays to determine the seriousness of the infection. Then, the dog can be treated with injectable medications. The total cost of the treatment can be anywhere from $350 to $1000. As is the case with most canine illnesses and disorders, prevention is better than cure, and considerably less expensive.
What Happens After Treatment?
If you don’t get heartworm protection for your dogs, and treatment is needed, the most important thing you have to do is keep your dog quiet. You may have heard people say “I shouldn’t have let my vet give my dog those injections for heartworm – if I’d just let it run its course, my dog might be alive today. The injections killed him!”
This is absolutely not true. The injections will kill the heartworms without endangering your dog. When dogs die following injections for heartworm, it’s because the dog was allowed to exercise instead of remaining quiet. As the heartworms die, they begin to fragment and the pieces can end up lodged in the blood vessels – the flow of blood is impeded, and the dog dies during exercise. So if your dog has heartworm, and has been treated, curtail the exercise for several months. During this time, your dog might enjoy playing quietly with a stuffie that doubles as a puzzle toy – he’ll get some mental stimulation and something to snuggle with while foregoing vigorous activity.
Can I Just Give My Dog More of the Preventative Treatment?
Well, you could. Heartworm is prevented, and treated in the very early stages, using ivermectin. It works to slowly kill off young heartworms, and if you just go with this treatment, in a couple of years most of the heartworms will die off. However, in the meantime, they’ll be doing irreversible damage to your dog’s heart and blood vessels. You’re far better off to go with the treatment that your vet recommends, and keep your dog quiet during the recovery period.
That said, once heartworm takes hold, as I’ve already pointed out, treatment can be expensive. If there’s no other alternative, more ivermectin is better than no treatment at all.
Do I Still Have to Worry About Heartworm Protection for Dogs in the Cold Months?
You should have your vet give your buddy heartworm protection for dogs year-round. Missing a month or two might not be a big deal, but if you miss more than that, then you’re risking infection. Another good reason not to skip heartworm protection for your dogs is that most of the preventative medications available today also offer protection from tapeworms, roundworms and whipworm, which can attack your dog at any time of the year.
Do Dogs Ever Outgrow Heartworms?
No. Young dogs can outgrow a number of conditions. Just as an example, when I adopted Janice, she had a heart murmur. I didn’t worry about it because heart murmurs are very common in puppies, and they almost always outgrow them. By the time I took Janice in to Dr. Kim for her 6-month checkup, the heart murmur was gone.
Heartworm is a whole other thing. A dog will never “outgrow” heartworms. It’s an infestation, not a condition, and if not treated, there is only one outcome – your dog will die.
I’ve Heard That Heartworms are Treated Using Arsenic – Isn’t This Dangerous?
Arsenic used to be the treatment of choice, but now there are safer products available. I want to caution you, though, that the supposedly “natural” heartworm remedies that you might buy online are usually not effective. If you want to be sure that you’re getting an effective heartworm prevention for your dogs, you’re better off going with what your veterinarian recommends. You can, though, buy reliable heartworm testing preparations online for your dog that will identify whether or not your dog has heartworm. They’ll save you a trip to the vet for treatment, if they come up negative. If they’re positive, though, get your dog to the vet ASAP. And, as I keep saying, you should still get heartworm treatment for your dogs.
Heartworm is a devastating disease that will break your dog’s heart, and yours as well if left untreated. That’s the bad news. The good news is that heartworm prevention for dogs is easy and inexpensive. It should always be part of your veterinary health regime. Keep in mind, too, that heartworm prevention for dogs has to be done regularly – a “one off” or “every so often” doesn’t do it, because heartworm protection is not a vaccine. Ideally, it should be a monthly thing. Your veterinarian can advise you as to the best heartworm protection for your dogs.