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Dog Heartworm - Preventing, Diagnosing, and Treating Heartworm Disease in Dogs



Dr. Sudeep Wahla
Prestige Animal Hospital

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

Heartworm disease is exactly that, a worm that lives in the heart. People think a lot of times when they hear the word worm, "Oh, my dog already had a test for worms." The standard test people do is a fecal test or a poop test, and that does not detect heartworm disease. Heartworm disease is detected by blood. Basically, it's transmitted from mosquitoes. The larva from the mosquito goes, develops into a worm, which lives in the heart, hence the name, heartworm disease.

How does my dog catch heartworms?

It definitely can catch heartworms from mosquitoes biting the dogs.

Can dog heartworms be prevented?

Yes, they can be prevented, very, very much so, actually. It's a completely preventable disease and a potentially fatal disease. How they can be prevented, there are oral tablets or injectable medications that can prevent the larvae from developing into adult heartworms. Before, back to the other question, I said mosquitoes biting, I guess a better word would be feeding because I don't know if they necessarily bite you.

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

Well, you could go from mild to moderate to severe signs, so I'll start between them and try to break it down to the best of my ability. A lot of dogs can go asymptomatic, which means they don't show clinical signs at the beginning—the early stages of disease. As the disease progresses, you might notice just a slight cough.

As we start to get into more moderate and severe signs, sometimes when you bring them in for an exam we can hear a heart murmur. They may get enlarged livers, they may get enlarged hearts. They may get fluid that backs up in their lungs and the abdomen. But the signs that you would be able to hear at home would be more difficulty breathing, exercise intolerance, sometimes they'd have bulging ribs cause they can't catch their breath. The most severe sign is it eventually does progress to death, unfortunately, if left untreated.

Is there anything that you would add in terms of those middle to late-stage symptoms?

Panting at rest on top of the cough, sometimes some dogs just pant because they can't catch their breath because their lungs have been affected as well. That'd probably be the only other thing I would add to that.

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

To stabilize your heartworm disease, the first thing we'd have to do is confirm the stage. The other thing that we'd recommend immediately is restricting the exercise. Even though they might still want to go out, don't let them. Once you get these symptoms stabilized, then we make a treatment plan determined by physical exam and further testing on your pet. Once we do the treatment plan and testing and treatment has been initiated, then we put them on a regular regimen of prevention. That being said, we could avoid all those if we start prevention and keep them on prevention as they grow.

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

We could start prevention as early as eight weeks old, but the first testing can be done at the age of six months old.

How will a veterinarian diagnose heartworm?

Well, we have a very simple blood test actually, that most veterinarians run in clinics, I know at Prestige we do. It only takes about three drops of blood and it takes us 15, 20 minutes to get the results, to see if the heartworm test is negative or positive. If that's positive, we may follow up with some other testing, such as X-rays, ultrasound of the heart and some other blood tests, but that's the mainstay and number one test that we start with.

Why is early detection and diagnosis of heartworm so important?

Early detection and diagnosis is important because that way we can avoid the worm burden. What the worm burden means is the number of worms that have accumulated and can cause issues. Worms, just for your knowledge too, can grow to about a foot long. Imagine a foot-long warm living in a small dog's heart, and there could be hundreds of these worms. They can be very symptomatic as they start replicating and reproducing inside the system.

So early detection and diagnosis is important in the prognosis because we can avoid the eventual. most serious, severe complication of death and initiate treatment that may be more effective. But please, other than treatment, prevention, prevention, prevention. A lot of times people get overwhelmed by the first few visits and tend to overlook heartworm disease. It is important to protect your pets against this.

FAQ - Dog Heartworm


Dr. Sudeep Wahla
Prestige Animal Hospital

What are the possible signs that my dog has heartworms?

The science can vary pretty significantly. It varies from mild to moderate to severe to worst cases, even death. Some dogs go asymptomatic at the beginning, meaning they're not showing any clinical signs or symptoms, which solely could progress into a cough or just more exercise intolerance, getting tired easily.

As it progresses into the more moderate, severe signs, you see breathing issues, bulging rib cage, trying to catch their breath, a persistent potential cough. In some dogs, we can hear a heart murmur because remember this is a heartworm, it goes through the blood and lives inside the heart. So it affects the heart which can back up and eventually lead to fluid in the abdomen, fluid in the chest, and it can lead to enlarged hearts and enlarged livers as well. So as far as clinical signs, exercise intolerance, coughing, panting, difficulty breathing, losing weight, not eating as much. These are some typical signs you could watch for.

Is heartworm painful?

It’s hard to say in pets whether it is painful. I don't think the worm as it travels itself is necessarily painful, but as they develop these symptoms, discomfort and pain follows. The inflammation that the worm causes can lead to pain as well inside the body.

Are heartworms visible?

They’re not visible. It's not like any worms that you could see in the poop or the stool, sometimes when dogs do have internal intestinal parasites, as this is one that lives in the bloodstream. The only way to really visualize them is with the use of imaging like x-rays or ultrasound. So they're not visible on just examination, you need other special tools to help you take a look at them.

Is heartworm prevention necessary?

Yes, heartworm prevention is necessary. They've detected heartworm in every state in the U.S. and it is of growing concern because people in states that didn't have it before but now are having it didn't have their pets on prevention. So for example, I live in an area where we do get coyotes—coyotes can transmit it because it's transmitted from mosquitoes, so if a mosquito bites a coyote and then bites your dog, they can get it. So it is represented in all 50 States so, yes, all dogs need to be protected.

How can we prevent heartworms?

Heartworms are prevented by an easy oral chewable tablet or an injectable that lasts six months. I prefer the latter because you don't skip doses, you don't have to retest, and you know your pets are getting the prevention they need.

Does my indoor dog need to have heartworm prevention?

So there have been studies and some of these studies have shown that even 25% of pets that are indoors can get heartworm. You might ask, “How how can my dog get heartworm if they’re only indoors? The same way that we get mosquito bites and we're indoors; a mosquito can fly inside and bite your pet or feed from your pet. Som yes, even indoor pets can get heartworm or you take your indoor dog for a walk or they go out for potty. So there are cases in which indoor dogs do tend to get heartworm as well, so they also need to be on prevention.

What’s the earliest that my dog can be tested for heartworms?

Six months of age. We could put them on prevention much earlier before that, but the time to test them to see if they have adult worms - at the earliest - would be at six months.

If you still have other questions and you'd like to reach out to us, you can call us directly at (909) 329-2860, you can email us, or you can reach out on Facebook.

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