Canine Heartworm Disease – FAQ

Hi, I’m Dr. Jessica Bianco from Dalton Veterinary Practice. And I’m here with Miss Rosie, one of our heartworms survivors. And she’s going to help me tell you guys a little bit more about heartworms in your pets and answer any questions that you guys have. Rosie’s mom Liz is going to help me by asking the questions. So let’s get started.

What are heartworms?

Heartworms are just like what they sound. They’re an intestinal parasite that grows and turns into a long, thin white worm. And they specifically like to live in the artery that connects the heart to the lungs.

Where exactly are heartworms found?

Heartworms are found and transmitted in bloodstreams of cats and dogs specifically. And then they’re transmitted by mosquitoes. When a mosquito bites a cat or dog that’s infected, it gets the baby worms, and then it can transmit those to another pet.

What is the heartworm life cycle? And why is it important to understand?

So the heartworm life cycle starts as a tiny baby heartworm that we call microfilaria. And that is what is taken up by a mosquito. It matures inside the mosquito, and then a mosquito can bite an uninfected dog and transmit the baby worms into their bloodstream. Once those baby worms have a chance to mature over the next six months, they become the adult heartworms that you see in the heart. When you have multiple adult heartworms, they can start to reproduce and create more of the baby heartworms to then infect more mosquitoes.

How common are heartworms in dogs?

It kind of depends on the area of the country that you’re in. Since they’re transmitted by mosquitoes, they’re very common in this area of the country. In the Southeast, you pretty much find a mosquito year round. And so the estimated prevalence, at least in dogs in this area is that about 20% of dogs are infected with heartworms.

How does my dog’s lifestyle affect her risk for heartworms?

Any increase in exposure to mosquitoes is going to increase your dog’s risk of contracting heartworm disease. Also, if you’re in an area near other dogs or cats that are infected, those mosquitoes have a higher likelihood to infect your dog.

Are certain breeds predisposed to heartworms?

Not necessarily.

Can heartworms be transmitted directly to humans or other pets?

An infected dog or cat cannot transmit it directly to another pet. It’d have to go through the mosquito vector.

How can I control heartworms in my dog’s environment?

The best way to control heartworms in your dog’s environment and limit your pet’s exposure is to do anything you can to treat your yard for mosquitoes and minimize exposure to mosquitoes. And then we’ll talk more about heartworm prevention for if they are bitten by mosquito.

Does my dog need year round heartworm prevention?

Yes. Especially in this area of the country, we absolutely recommend year round heartworm prevention for all dogs.

How much does heartworm disease prevention cost?

There’s multiple different forms of heartworm prevention. Some are monthly pills, which average in costs from about $10 to $20, depending on the type of medication and the size of your dogs. There’s also injectable heartworm medication that lasts either six months or a year, depending on which one you choose. And in general, that ranges from about $80 to $120 per year, depending on the size of your pet.

When should I start giving my dog heartworm prevention?

We started giving dogs heartworm preventions when we see them for their puppy visits around six to eight weeks, depending on their size and the type of medication. And we recommend keeping them on it from there on out.

Can my dog get heartworms, even if she is on heartworm prevention?

It’s very unlikely if given correctly, if you are on time with getting your dog’s heartworm prevention filled and administering it to them or getting their yearly or every six months shots. It’s very unlikely that your dog would get heartworms.

What if I miss a dose of my dog’s heartworm prevention?

We’ve all done that. Even me, if you miss a dose, the best thing to do is to let us at the veterinary office know, that way we can document it and know which month was missed, and then give it as soon as you’re able. If there is a gap of about a month or two in between doses, sometimes they can be positive on the next test. And we’ll talk more about the importance of a yearly heartworm test.

Why is it important to get my dog’s heartworm prevention from my veterinarian?

So there’s no over the counter medication that’s labeled to prevent heartworms. So you’ll have to go through your veterinarian to get it. All veterinary offices will carry some type of heartworm prevention, be it injectables or oral or topical, just at the discretion of the veterinarians. You can also get them from online pharmacies. Sometimes those medications are from questionable sources and may not have been handled correctly. So we do recommend getting it straight from your veterinarian so that you can make sure that you get all the benefits such as rebates or guarantees.

How has my dog tested for heartworms?

A heartworm test is a simple blood test that almost all clinics can run at the time that your pet is in the office. You just need a few drops of blood. And that test is actually testing for something that female heartworms emit.

Can I give my dog heartworm prevention without a blood test?

No, it can be really dangerous if your dog does already have heartworms to start giving them heartworm prevention, especially without knowing, because you could start killing baby worms and they can react to that.

Are there other tests used to confirm the presence of heartworms?

If we suspect heartworms in a dog, or if we have that initial positive blood test, we’ll typically recommend a confirmatory test run at an outside lab. Oftentimes we’ll look at a drop of blood under the microscope to look for the microfilaria or the baby heartworms. Also, we’ll listen to their heart and lungs to see if we hear any changes. And often we’ll recommend chest X rays to evaluate the heart size and shape and the health of the lungs before proceeding with other treatments.

Is it possible for my dog to have heartworms even if her blood test is negative?

Yes, it’s rare, but false negatives are possible, especially since it’s detecting something that female heartworms emit. If you have a male heartworm infection that could be negative, but still have a few heartworms in the heart. It’s very rare though.

How often should my dog be tested for heartworm disease?

All of the veterinarians and manufacturers of heartworm prevention medication recommended and require a yearly heartworm test to keep your pet on heartworm prevention.

Does my dog still need heartworm testing if she is on year round prevention?

That’s a really good question. Sometimes confusing to answer, but the answer is yes. And there’s a couple of reasons why. The main reason why is that, unfortunately, no medication or prevention is 100% effective in every situation. And there’s a lot of variables at play. If you’re late giving a dose, or if you miss a dose, sometimes those things can even go unnoticed. And it’s really important that we make sure to know every year that the dog is still negative. And if they were positive, we would want to know as soon as possible. So we don’t like to wait more than a year in between.

Why is early detection of heartworms so important?

Heartworm disease causes a lot of damage, as you may imagine because of the location that they live in. They damage the heart and the lungs and can also cause systemic reactions throughout the body, through the bloodstream. The sooner we find the heartworms and can get rid of them, the less damage they do. But each day that heartworms are in your dog system, they are causing damage that cannot be reversed.

My dog had a positive heartworm test. Now what?

If your dog tests positive for heartworms, we’re probably going to recommend a confirmatory test just to make sure things are valid. And then we’ll go over options to further evaluate your pet’s health, as well as talk to you about how we can kill adult heartworms if that’s a route that’s safe for your dog.

What can happen if my dog is not treated for heartworms?

If left untreated, heartworms continue to live and they can live for several months to years in your dog’s system. And because they’re living in such a vital part of your dog’s body, the heart will change and decompensate over time. And the lungs will start to have an inflammatory reaction. These combined together can severely affect your dog’s ability to pump blood and breathe. And it can be fatal.

Is heartworm damage permanent?

All of the damage that the heartworms do while they’re inside the body is permanent. Sometimes we can reverse some of the symptoms, but all of the damage will still be present.

Is treatment painful?

Heartworm treatments are a pretty involved process that we’ll go into detail about in a minute. The medication used to kill adult heartworms can be painful, which is one of the reasons why we much prefer to prevent heartworm disease rather than have to treat it once they’re there.

Is treatment safe?

Heartworm treatment is very involved and requires some stays in the hospital. It is safe. It’s much safer than allowing heartworms to go unchecked. There are some risks, especially to certain pets and we’ll go over those with you if your dog has to go through heartworm treatment.

How effective is heartworm treatment in dogs?

We have a specific protocol that was developed by the American Heartworm Society and it’s 99% effective at killing heartworms.

How many treatments will my dog need?

So Miss Rosie has been through this and hopefully she’ll help me tell you guys, your dog will get a total of three in hospital treatments for heartworms spaced out over four months and that’ll involve four different injections.

Do I need to treat all pets in the home if only one has heartworms?

If one of your pets comes up positive for heartworms, our recommendation is that you get the other dogs tested. If they are negative, we recommend starting them on preventative.

How quickly will my dog’s heartworm disease progress from one stage to another?

Each dog is very different in this respect. Some dog systems can handle heartworms a lot better than others. Some dogs decompensate very quickly within a few months after getting infected with heartworms. So it’s a difficult question to answer, but it’s a really good question to ask to know what to expect and how to proceed.

Is the stage of my dog’s heartworm disease reversible?

So if we’re able to do x-rays and evaluate heart and lungs prior to starting treatment, we can kind of stage your dog’s heartworm disease to see how severe it is. If your dog’s already having symptoms of heartworm disease, like coughing, fainting, or exercise fatigue, sometimes we can reverse those symptoms. The damage to the heart and lungs that’s causing those symptoms will still exist. But oftentimes once the heartworms are killed and we’ve treated their heart and lungs, they may still be damaged, but they can function at a much higher level.

How much does heartworm disease treatment cost?

Heartworm disease treatment is very expensive. Although we do have some ways to help you guys out. And if that happens to you, it’s generally around $1,000 to $1,500, depending on the size of your dog.

Can I just give my dog her monthly preventative medication to clear an infection?

Good question. But no. Monthly preventatives are labeled and proven to kill baby heartworms, but they will not kill the adult heartworms that are living in your dog’s heart. So while it may kill the baby heartworms and prevent more adults, you’re allowing the adult heartworms that are already in there to continue causing more damage.

Why is it important to restrict my dog’s activity during treatment?

If you can kind of imagine there’s big adult heartworms in your dog’s heart and towards their lungs. And there’s also thousands of baby worms circulating throughout their bloodstream. As we start to kill the baby worms first, and then second the adult worms, there’s really nowhere for them to go except to die in the bloodstream. And as those are moving around and being processed by the body and excreted, your dog is at risk for potential reactions, throwing clots to different parts of their body. And the more active they are and the higher their blood pressure gets, the more at risk they are to having those adverse events.

Can my dog go back to regular exercise after treatment?

Yes. Once we’ve confirmed that all the heartworms are gone and they’re not having any excessive symptoms, they can go back to regular activity.

Can heartworm disease resolve on its own?

Heartworm disease very rarely resolves on its own. I’m not going to say that it’s impossible, but generally it would take several years for that to happen. And a lot of precautions along the way to make sure that they don’t get reinfected by more heartworms. And several years of allowing heartworms to live in the heart could be deadly.

Can heartworm disease recur after treatment?

If you don’t keep your dog on heartworm prevention, then yes, heartworms could reinfect your dog. And there’s no such thing as a lifelong immunity to heartworms after you’ve already had it.

How often should my dog be rechecked after treatment for heartworm disease?

After the initial heartworm treatment is completed, we will recheck a heartworm test six to 10 months after that final injection. Hopefully that one will be negative and your dog will still be on prevention. Then they will go to just an every year schedule like other dogs.