How to Prevent and Treat Heartworm Disease in Dogs
How does a dog get heartworm?
It's one of the first questions we need to think about: how does a dog even get heartworm? You're saying it's a heart and a worm. The heart's pretty important, right? I don't want worms getting in there.
Heartworms are actually transmitted by mosquitoes. Mosquitoes carry this kind of immature form of the worm, which is really tiny. We're not going to see it; it's small enough to circulate in our dog's blood. A mosquito comes, bites your dog, and as the mosquito is biting, in the saliva, it can pass these little things called microfilaria. It's a very immature form of a heartworm. It gets out of the saliva and goes into the dog's blood system. It enters those little vessels where they were just trying to get their meal from. Now they've introduced that type of immature worm into the body.
Down here in the South, unfortunately, we see mosquitoes year-round. There are a lot of these heartworms out there, and we do see a lot of dogs coming down with heartworm disease if they're not on a good preventative program.
How often should dogs get tested for heartworm?
While we get you on a good heartworm prevention, our recommendation is to get you a heartworm test at least every two years, as long as you're on your prevention, which is a kind of year-round control.
We still want to test you every two years just in case. None of our medications is going to be 100% effective, so we want to make sure nothing slipped through the cracks during that time.
We like to test with a little tiny blood sample. We just need a couple of drops of blood, put it on a little thing, and it takes about 10 to 15 minutes. It's nice and fast. We test them to make sure they don't have heartworms. These tests are actually checking for a protein that adult females will put into the blood. If that protein is present, it'll come back positive on our heartworm test. If it is positive, we will let you know, and then we have some options on how we want to treat heartworm disease.
Learn more about Why We Heartworm Test Your Dog
What are the treatment options for heartworm disease in dogs?
There are two different options: a slow kill or a fast kill. We like to get them out of the body as soon as possible. There's an American Heartworm Society that goes through all these gurus of heartworm disease. They still recommend, ideally, the fast kill approach. That is something we would refer to one of the local general practices. It's a more full-service clinic, not just the vaccine clinic like ours, where they can do that whole protocol for you.
Initially, we start with an antibiotic called doxycycline. There's a little bacteria in these heartworms called Wolbachia. It's a fun word to say. Those little bacteria can also cause some issues, so we want to get you on an antibiotic to make sure that the bacteria are gone. Then we're going to keep you on a monthly heartworm prevention for the next couple of months. In that period, you would have the option to do the fast kill method.
The slow kill method takes longer for us to get rid of the worms in the body. The longer they're in there, the more chance they might do some harm, but cost-wise, it is easier on the wallet. Sometimes we'll pick that slow kill method, which involves year-round heartworm prevention and an initial dose of doxycycline antibiotic. We're really waiting for those adult worms to die off on their own. It may even take one to two years before they're all gone from the body. That's what happens if you test positive while you're in one of our clinics.
What happens if you don't treat heartworms in a dog?
Unfortunately, these adult worms start off and as adults, they'll actually go and get into the area of our arteries in our lungs, the ones close to the heart. They're going to cause some inflammation and may cause some coughing. The more and more those adults keep growing and making new little babies and more adults, they're going to start backing up and can go into the vessels of the heart themselves. That's where they got this name heartworms from; they get into the heart. Now, we're causing inflammation in the heart that can cause some chronic secondary changes in the heart as well as the stuff we're seeing in the lungs. We want to get them out of there as soon as possible.
What can I do to prevent heartworm in my dog?
It's pretty easy to prevent these guys. There are oral medications or injectable medications. There are even some topical medications, especially for our cats. We don't use many topicals for dogs, but there are some other options out there. There's an injectable called ProHeart, given either every six months or once a year, or the oral medication that we take once a month. The once-a-month kind keeps us protected against any time throughout the month that a mosquito might have bitten our dog. We can kill them all off every month before they get to the adult stage before they can do any harm.
Do all dogs need heartworm prevention?
In the south, I would say yes! Unfortunately, up north, I used to work in New York, Pennsylvania, Illinois, we had different seasons, and we didn't see mosquitoes for a good four or five months of the year, and sometimes we would get them off during that time. But down here, we do see mosquitoes year-round. I like to get them on heartworm prevention year-round to protect them.
Even if they're indoor only, they're still going outside to pee and poop. You still have the chance of mosquitoes coming in the house that could bite them and transmit these things. I would definitely recommend all dogs be on heartworm prevention.
How often does a dog need heartworm prevention?
It really depends on which product we're going to use. Are we using that six-month injectable product? Is it a 12-month injectable product? Or is it going to be one of these every month products that we give them? The nice thing about our every month product is a lot of times it's also mixed with a deworming medication. We can combine our heartworm prevention with our intestinal parasite prevention. Some of them combine some flea and tick control. We can tailor things around what you think is going to be best for your own dog.
Why is early detection and diagnosis of heartworm so important?
Think of this being like somebody with cancer. The earlier you detect it, the greater your chances of success with an easier form of therapy treatment and resolution of the disease. We'd much prefer to see if a dog's going to get the disease. We tested them last year, and they didn't have it. We tested them a year later, and now they've got it. They haven't had the heartworms for very long, but if we see dogs coming in that have never been on prevention, and these dogs are 6, 7, or 8 years of age, who knows how long they've had it. By this time, many changes are going on with the body involving the heart, the lungs, and the liver, and if there is damage to the heart, lungs, and liver, it can be irreversible.
We can still treat the disease, but some of the damage is done, so the earlier we can catch heartworms in dogs and get them on treatment, the sooner we can help prevent this cascade of problems that can occur from the disease.
Can a dog pass on heartworm to another pet or person?
Good question. No, they cannot. It is kind of interesting. I'm going to give a little bit of inside here. A lot of times when dogs come in, and we do a heartworm test, one of the things that I often ask as I'm getting the blood sample is if that particular pet parent happens to know how dogs get heartworms. Most of them don't know. Most people don't know how dogs get heartworms even though they're giving their medication to their dog on a monthly basis or getting the six or 12-month injection.
It makes me realize that, somehow, as a profession, we have failed to educate people about this importance. I think people understand the importance of it, but it's more important to recognize how they get them in the first place because this gives you a sense of why it is a problem and a continual problem, particularly in the southeast part of the US. Quite simply, how do dogs get heartworms? Only from mosquitoes. So they cannot pass it to people. They cannot give it to another dog. Only mosquitoes can transmit heartworms from an infected dog to a dog that's not currently on heartworm prevention. That's it. Mosquitoes. That's the only way it can be spread.
How common are heartworms in dogs?
It depends on the part of the country. In this part of the country in the Southeast, unfortunately, we do see heartworms. It is a huge problem throughout the southeastern US, mainly because we have had mosquitoes for a very long time. To be more specific, we potentially see heartworms or mosquitoes year-round. Mosquitoes start to emerge when the temperatures get into the low 50-degree range. So even in the months of January and February, we are always going to have some days where it's in the fifties or even up into the sixties. Even in the wintertime, we expect that. We're not going to see the mosquitoes in January and February as we do in August, September, and so forth, but the point is that we do see mosquitoes year-round.
We do have a heartworm risk all year round in this part of the country, from about Virginia all the way south. It is a horrible issue in the Gulf states, like Florida, Mississippi, Alabama, Texas, and Louisiana, because they also have a lot of low-lying watery areas. But particularly in the southeast, it's the biggest problem. Some places where it's extremely arid out west are not so much of an issue, but it does exist on the entire east coast and a significant part of the west coast.
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