What is heartworm disease, and how can it affect my dog?

Heartworm disease is a disease that dogs and cats can only get from mosquitoes. There's no other way they can get it. It is a mosquito-transmitted disease, and it is a potentially life-threatening disease. It is crucially important that we protect your dogs. The good news is we have a variety of ways to protect your dog against this potentially deadly disease.

Dr. Bob Parrish
Carolina Value Pet Care

How would my dog catch heartworm?

Only from mosquitoes. There's no other way. Here's the consideration: your dog never has to see another dog to get the disease. The way it works is a mosquito would bite an infected dog, and then it goes through a little series of transmissions or mutations in the mosquito. Then that infected mosquito would bite an unprotected dog, a dog that's not on prevention. That's the way it's going to spread. There was a study done back about five or seven years ago in, maybe ten years ago, somewhere in Arkansas. They discovered that at least in this area, and I'm sure it's no different here in the North Carolina area than it is in Arkansas, the average dog that is outdoors at night was getting about 3000 mosquito bites per night. What are the odds of a dog getting transmission of heartworm disease? I know most dogs are inside the house. But again, think about it. How long does it take for you to go outside and get a mosquito bite during the peak of mosquito season? Some people are going to be more resistant or more of a magnet for mosquitoes, but the other consideration is that a lot of people think, oh, my dog's got this really long hair. How is it going to get a bite? We know the mosquitoes primarily target the face of dogs. Dogs don't react the way we do where we get the little itchy places. We know that the face is the primary target for mosquitoes, even in hairy dogs.

Learn more about Why We Heartworm Test Your Dog.

Can heartworm in dogs be prevented?

Yes, we've had preventions available for years and years now. We keep getting better preventions nowadays. One of the concerns that we're starting to see in better new medicine is that because some of these medications have been around for 30 to 40 years, we are unfortunately starting to see some resistance with some of the heartworm preventions, primarily through what we call the ivermectin-based preventions. You've probably heard of Heartgard or Iverhart, which are ivermectin-based. We are starting to see issues with heartworm resistance in those situations. We've been seeing this for about ten years now. So this is nothing new. It is becoming more of an issue, though. The beauty is that, yes, we have many different ways of preventing heartworm disease very easily nowadays.

What are the signs in my dog that would indicate they may have heartworm?

There are so many variables if your dog is even going to develop any signs or symptoms of the disease. It depends on how many heartworms they have and how long they've had them, and we can test for that. We routinely test dogs for heartworms, but the test will just tell you, yes, your dog has the disease, or no, it doesn't. It doesn't tell us anything about how long your dogs have the disease or how many heartworms are living in the heart, but it's not uncommon for dogs to have 30, 40, or 50 of these heartworms living in your their heart, in which case they'll eventually start to migrate to the lungs. That's when we really started getting into complications. It's easy to diagnose, so if you suspect it, bring them in. Getting back to the signs of symptoms. First, we start to look for the early signs in dogs, like exercise intolerance. Sometimes, they're just getting a little bit older, but it could also be because of heartworms. It can escalate into coughing episodes primarily at night, early in the morning, or after exercise. As it becomes more progressive in dogs, they will start to become more lethargic. They don't have the energy that they used to have anymore. We mentioned exercise intolerance, but a lot of these dogs would just seem older. Then we get to the point where, in extreme situations, dogs are having a real hard time breathing. In some cases, we might get leakage of fluids into the abdomen. So they come in, and their belly starts to swell. Those are extreme and severe cases of heartworms. Generally, the first two things we'll see are exercise intolerance and coughing.

What are some middle to late-stage symptoms of heartworm?

Dogs have a tough time breathing, getting up, and just not wanting to get engaged as they used to with family members or other dogs, and situations where we do start getting liver involvement start leaking. They start looking bloated in the abdomen because they started leaking fluid into the abdomen.

What can be done to stabilize my dog's heartworm disease?

It depends on the stage of the disease. Obviously, if we catch it when your dog's quite young, then we can treat it with great success and minimal issues associated with the treatment itself. If it becomes more progressive, we have to get involved with treating the disease, but also getting some medications for the heart and the fluid buildup, and things of that nature to try to stabilize the dogs.

How soon should I bring my dog in to see a veterinarian for heartworm prevention?

We like to get started with puppies the first time we see them. We start seeing puppies for their first vaccine at 6, 7, and 8 weeks of age. We like to get those puppies started with heartworm prevention right away because a dog can get bitten by a mosquito and become infected on the day they're born. So the sooner we can get them on prevention, the better for your dog's protection because this is a year-round medication. We need to prevent mosquitoes year-round. That is important to recognize. Yes, we don't see nearly as many mosquitoes in January and February as we do in June, July, August, or September, but they can be a year-round problem in this area. They start to emerge when temperatures hit about 50 degrees or so. So we should be aware that mosquitoes can be year-round in this area. We definitely need to keep your dogs on prevention all year nonstop.

How will a veterinarian diagnose if my dog has heartworms?

We very simply do lots and lots of blood tests for heartworms. Essentially, we take about two or three drops of blood. We have a test that takes 10 minutes to run. We also have two different types of tests for heartworms. We have one test that's just heartworms only, and for those dogs that do spend a lot of time outside, we strongly recommend doing the test that is not only for heartworms but also tests for Lyme disease, another tick-related disease called anaplasmosis, and another tick-related disease called Ehrlichia. So we do have those two different tests, and the one that does more costs a little bit more, but it can be well worth it, especially if your dog spends a lot of time outside.

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.

If you still have other questions and you'd like to reach out to us, you can call us directly at (704) 288-8620, you can email us, or you can reach out on social media. But please do reach out, and we'll get back to you as fast as we can.

Dog Heartworm Disease - FAQs

Dr. Bob Parrish
Carolina Value Pet Care

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 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 always are 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.

What is the cycle of heartworm, and how will this information be beneficial to the treatment of my dog?

That's a good question, too, because it actually gets into the core of how heartburn prevention works. What exactly is it doing now? Essentially, a mosquito will bite an infected dog and then transmit it. It will go through a series of stages of development, a couple of stages that avail within a mosquito. Then the mosquito bites an unprotected dog and squirts this larva into the dog as it's sucking out the blood, in which case, there's more larval development inside the dog. Then it develops into adult heartworms, which live primarily in the heart but can also migrate into the lungs. How does heartworm prevention work? How does that fit into this whole sequence? When we think of heartworm prevention, we think we're preventing getting it in the next couple of weeks or six months. But it actually works backward. It is working to protect or eliminate any of the heartworms, the development, or the larva the previous 30 days when we're giving the once-a-month medication. If we're giving the medication, it works backward over the last 30 days. That's why it's imperative that you've got to keep your dog on prevention once a month. Don't try to cheat and go every 45 days or certainly not every couple of months because you're missing that window when the larva can develop and go on to the adult stage. Again, if you're going to start with prevention, be consistent. Make sure you're giving the medication every single month, about every 30 days. Let's be precise, how about every 30 days? If you get it every 30 days, your dog's going to be protected. But if you start skipping days and if you forget to give it, that's when we can run into problems. That's why we do have a six-month injection, and a 12-month injection for situations where we forget to give it or your dog doesn't really like to take the chewable tablet. We also have one topical liquid for people who don't want the injection or if their dogs won't take the chewable tablets. So essentially, that's the life cycle. The cycle starts when the mosquito bites an infected dog and sucks its blood. The larva develops, and the mosquito transmits it to an unprotected dog through a mosquito bite. Then the cycle just keeps on going that way. So please, the take-home message is to make sure you give your dog heartworm medication when it is supposed to be given.

Can my indoor dog get heartworm?

Absolutely. Obviously, we're not going to have nearly the amount of mosquito problems inside somebody's house unless you have kids going in and out all the time or the dog's going outside, or you have a doggie door, for example, where they have a little trap door where the mosquitoes can come in. But indoor dogs can get them because mosquitoes can get in the house. Granted, there's not going to be near the risk inside the house as going outside, but it's still a risk. I know very few dogs that don't go outside. There is that one rare dog that never ever goes outside, but guess what? If you bring them to a veterinary clinic, that's going outside. Keep in mind the more time a dog spends outside, the greater the risk of exposure because the more frequent mosquito bites can get. Hopefully, that'll give you some information about heartworms. If there's one thing I want you to take away from this, it's mosquitoes, mosquitoes, mosquitoes. That's the only way they can get the disease.

If you still have other questions and you'd like to reach out to us, you can call us directly at (704) 288-8620, you can email us, or you can reach out on social media. But please do reach out, and we'll get back to you as fast as we can.