Next month (April) is Heartworm Awareness Month. Heartworms, heartworm prevention, heartworm testing, and heartworm treatment is a huge topic in veterinary medicine. There are a lot of different products out there, each one with a load of research and data showing how they are the best and safest product to prevent heartworms in your pet. What I am not going to do is endorse any one of these products. Your veterinarian will tell you what he or she recommends and why they think it’s the right product for your pet. What I will do is explain how your pet could become infected and why using a heartworm preventive and having an annual heartworm test is important. I am also going to explain what the treatment for heartworms is and why you do not want to put your pet through that.

So, what are heartworms? Well, heartworms are a type of roundworm. The natural host is the dog, but they can infect cats, ferrets, coyotes, wolves, foxes, sea lions, and in very rare instants, people. They are called heartworms because in dogs, the adults live in the heart, lungs, and associated blood vessels and they cause damage to those organs. If given enough time, this damage can be severe enough to kill. Cats and ferrets are affected a little differently than dogs are, so my discussion is going to mainly discuss dogs. The treatment is also different. If you want to know more about how cats and ferrets are infected and treated, talk to your veterinarian.

Your next question is probably, how can my dog get it? Which is a very good question to ask. Heartworms are spread by mosquitos. Adult female heartworms produce microscopic baby heartworms called “microfilaria” that swim all through the animal’s blood stream. When the mosquito bites an infected animal they suck up these baby heartworms and can then infect another dog, cat, fox, etc.

Heartworm disease has been diagnosed in all 50 states. As long as there are mosquitos and as long as some dogs go untreated and wild dogs, wolves, coyotes, etc., are out there, the likelihood of it continuing to spread, is a very real fact.

Alright, now that I’ve scared you and you’re desperately looking for your vet’s phone number, you’re likely wondering if you can get heartworms from your dog (no), if you get bit by a mosquito are you going to get heartworms (no), and once your pet is on the preventive, why does your vet keep having you do those annoying and expensive blood tests every year? You buy the medicine and give it as directed. So, why? Don’t they trust you? Are they just trying to make more money off of you (as if the medicine wasn’t expensive enough!)? Excellent question, I’ll tell you why. No one and nothing is perfect. That chew you swear you gave every month, you could have forgotten (I blame it on my husband, but that’s another story). Or, Fido could have spit it out or puked it up while you weren’t looking. The topical medication might have been washed off when your goofy lab went swimming in the water bowl again. Finally, the medication could have been manufactured or stored incorrectly. The medication could have been mixed into the chew wrong, the ingredients could have been stored or processed wrong. Any one of a hundred things can go wrong on the journey from processing to your dog’s body. Even an injectable product could have been processed, stored, reconstituted, or administered incorrectly. Nothing is infallible and that yearly test is a way to make sure that if your beloved fur-baby has somehow become infected, it doesn’t go from being something that can be treated, to something far worse.

Speaking of treatment, how is it treated and what if I decide not to use the preventive and just get the test yearly and hope for the best? Also, if my dog or cat gets treated for other worms once a year, wouldn’t that take care of the problem? I’ll answer the second part first. Unfortunately, not all deworming medicines kill all worms, just like not all antibiotics kill all bacteria. That’s just not how it works. The adult heartworm is a particularly difficult worm to kill and takes a specific type of medical treatment. The full treatment process involves starting a heartworm preventive to kill any baby worms, then antibiotics to kill bacteria released from the worms as they die, and steroids to treat the inflammation caused by the dying worms. The main medication, called melarsomine, is derived from arsenic and is given in the muscle over a number of treatments. For each treatment, your dog has to stay in the hospital for a few hours to make sure he or she doesn’t have any potentially life threatening reactions. It is an expensive and uncomfortable process that is not pleasant for you, your pet, or the veterinary staff administering the treatment. It is also not an easy medication to get a hold of. For a while, a few years ago, it wasn’t even available. Currently, the veterinarian ordering the medication has to prove they have tested, retested, and tested again using varying methods to prove the diagnosis (before you ask, yes, you’re more than likely going to have to pay for each of these increasingly more expensive tests). Ultimately, it’s a long, arduous process that costs more time and money than just giving the preventive would have to begin with. It could also cost you your dog.

So, if you have been giving your pet the heartworm preventive prescribed by your vet as directed, great job. Just remember that a yearly heartworm test is still recommended. If you haven’t been giving it or declined to get it at your last annual exam, I urge you to use this as your excuse to call your vet and ask about it. It’s a small price to pay to protect your best friend from a potentially life threatening disease.

For more information, check out https://www.heartwormsociety.org or call your veterinarian.