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Heartworms In Dogs - Symptoms and Treatments


Since 1967 the veterinary staff at Dalton Animal Care has made heartworm prevention for dogs an important part of our approach to preventive care. A heartworm infection can lead to numerous health problems up to and including early death. Therefore, heartworm prevention cannot be ignored. Our team is here to educate you and protect your dog from this terrible disease.

While outdoor playtime certainly offers numerous benefits, it also increases the risk of exposure to heartworm in dogs. This does not mean that dogs are completely safe indoors. It simply means that potential exposure to heartworm infection increases with more exposure to the outdoors.

Heartworm is spread through dogs via bites from infected mosquitoes. Living in GA, the presence of mosquitoes throughout the spring, summer and early fall months means greater chances for your dog to contract heartworms. Once a heartworm infestation occurs, it will become life threatening. Therefore, our goal is to implement a preventive program before your dog is exposed.

What Is Heartworm Disease?

Heartworm disease in dogs is a blood-borne parasitic nematode (roundworm) known as Dirofilaria immitis transmitted by mosquitoes.

Upwards of 30 species of mosquitoes can act as heartworm transmitters. Mosquitoes ingest immature heartworm larvae, called microfilariae, by feeding on either an infected cat or dog. The microfilariae develop further for 10 to 30 days in the mosquito's gut and then enter parts of the mosquito's mouth.

When an infected mosquito bites a dog, it injects larvae into the dog. The larvae then mature over a period of several months, eventually ending up in the right side of the heart and the pulmonary arteries. Once this occurs, they mature into adult heartworms in dogs, and can reproduce about six months from the time of invasion. At approximately eight months after the invasion, heartworm in dogs begin to produce a new crop of microfilariae that will live in the dog's blood for about one month. By the time this occurs, most dogs are showing significant heartworm symptoms, and their lives are in danger.

Featured Quote:

Any increase in exposure to mosquitoes is going to increase your dog's risk of contracting heartworm disease.

Video Transcript:

Dr. Jessica Bianco

Dalton Animal Hospital

 

Hi, I'm Dr. Jessica Bianco from Dalton Animal Care. And I'm here with Miss Rosie, one of our heartworm survivors. And she's going to help me tell you guys a little bit more about heartworms and 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 sort of 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 the 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 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 can pretty much find the 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.

Heartworm Symptoms - The Four Stages Of Heartworms In Dogs

Heartworm symptoms in dogs are divided into four stages. It is important to understand that individual stages are not always clearly identifiable and some stages can overlap, but the following information will help educate you about the four major stages, as well as their accompanying heartworm symptoms. The four clinical stages of heartworm begin when your dog has already become infected and the heartworms are present in the dog's heart:

Stage 1: In dogs, the first stage of heartworm will typically be symptom free. In this stage, the heartworms are present and settling into the heart. However, in stage one the disease has not yet progressed to the point where the heartworms will have produced a new generation of microfilariae and dog's body will not yet have produced antigens in an amount sufficient for detection.

Stage 2: Stage two of heartworms in dogs is accompanied by moderate symptoms including intolerance for exercise and a more lingering cough. The heartworms have been present long enough in the body for antibody production and probable microfilariae production. During this phase, heartworm disease may be detected with blood tests.

Stage 3: By stage three of heartworms in dogs, the symptoms of the disease will be very noticeable and have a big impact on your dog's health. Dogs continue to cough and experience fatigue after exercise, may be reluctant to exercise at all, and can have trouble breathing. During this stage, dogs may also cough up blood. By stage three, the disease is quite evident on x-rays. The worms in the heart and large vessels will be obvious on x rays.

Stage 4: Dogs in stage four of heartworm disease have very visible heartworm disease symptoms. These symptoms are accompanied by long-term implications for the dog's health. These dogs are very ill. The symptoms are similar to Stage 3 but more severe. Dogs will be reluctant to exercise, tired after exercising, and will exhibit a cough. They will probably experience trouble breathing as well. Testing may reveal the impact of the disease in the form of abnormal sounds within the dog's heart and lungs and an enlarged liver. Even with treatment, this stage of the disease carries a high risk of long term debilitation and possible death.

The severity of heartworms in dogs is directly dependent upon:

  • The number of worms present in a dog's body
  • The duration of the incubation
  • The response of the infected do, in fighting off the infestation

As heartworm disease progresses through each stage, treatment methods become increasingly invasive. This is a big reason why early detection plays a major role in the options and ability for your dog to recover. Remain aware of any changes in your dog's behavior. Keep an eye out for any changes in behavior that align with the symptoms of heartworm and if you do find that your dog is displaying symptoms that could be indicative of heartworm, it is important to make a veterinary appointment right away.

Other heartworm symptoms include:

  • Anemia
  • Fainting Spells
  • Right Sided Chronic Heart Failure
  • High Blood Pressure
  • Rapid Heart Beat

It is important to understand that the symptoms listed above are indicative of advanced stage heartworm disease. Unlike medications that are used to prevent heartworm in dogs, the medications that are used to kill an advanced stage heartworm infection carry a higher rate of potential side effects, can be painful for the dog and are costly to the owner. In addition, the treatment will require considerable downtime for your dog's normal exercise routine while the dog recovers from the infection.

Heartworm Prevention For Dogs

Heartworm prevention is given in the form of a monthly chewable. The chewables are readily accepted by most dogs as a treat. It is very important that the chewable be given once a month on the same day of the month to make sure that your dog is adequately protected. Side effects of the chewable medication are rare. However, as with any medication, please call if you notice any changes in your dog's health or behavior.

Featured Quote:

We absolutely recommend year-round heartworm prevention for all dogs.

Video Transcript:

Dr. Jessica Bianco

Dalton Animal Hospital

 

Hi, I'm Dr. Jessica Bianco from Dalton Animal Care. I'm here with Ms. Rosy, one of our heartworm survivors. 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. Rosy's mom, Liz, is going to help me by asking the questions. So, let's get started.

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 their exposure to mosquitoes. Then we'll talk more about heartworm prevention for if they are bitten by a 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 are multiple different forms of heartworm prevention. Some are monthly pills, which average in cost from about $10.00-$20.00 depending on the type of medication and the size of your dog. There's also injectable heartworm medication that lasts either six months or a year depending on which one you choose. In general, that ranges from about $80.00 to $120.00 per year depending on the size of your pet.

When should I start giving my dog heartworm prevention?

We start 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. We recommend keeping them on it from there on out.

Can my dog get heartworms even if they are 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-month 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. 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. 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 heartworm, so you'll have to go through your veterinarian to get it. All veterinary offices will carry some type of heartworm prevention, be it injectable, oral, or topical 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.

What You Need To Know About Heartworm Treatments

The first thing to understand is that there is a significant difference between heartworm prevention and heartworm treatment. Prevention is simple to do and is effective in protecting your dog from heartworm disease. Treatment options are used for dogs that are already sick because they have become infected.

The first step in heartworm treatments is obtaining a diagnosis. Most veterinarians use a battery of tests to determine the presence of heartworms in dogs. The first step in diagnosis of heartworm in dogs is to perform a blood test.

A positive heartworm blood test in the first step in diagnosis. If the blood test comes back positive, then the following tests will also be performed to determine the stage and severity of the disease in order to determine the most appropriate treatment plan:

  • A urinalysis, or the testing of a dog's urine
  • An antigen test determines the presence of adult female heartworms
  • Radiographs, or X-Rays to view the size and shape of a dog's heart. This is helpful because many dogs with heartworm develop enlarged pulmonary arteries, or have obstructions in the arteries leading to the lungs
  • Ultrasounds allows us directly view the internal structures of the heart and surrounding vessels, in order to assess the condition and function of the heart

During initial heartworm treatments, most patients are hospitalized to receive an adulticide, which is a medication that kills adult heartworms. The microfilariae in the body can be eliminated with a monthly prevention, which can be administered at home.

For more severe cases, such as dogs experiencing thromboembolic complications (in which a blood clot that has formed breaks loose and travels through the bloodstream to clot another vessel), hospitalization may be necessary for a longer period of time while heartworm treatments are administered. In some extreme cases, a surgical procedure may be necessary to remove adult worms from the right heart and pulmonary artery by way of the jugular vein. This procedure is recommended if the infestation consists of a high number of adult worms.

Featured Quote:

We'll typically recommend a confirmatory test run at an outside lab.

Video Transcript:

Dr. Jessica Bianco

Dalton Animal Hospital

 

Hi. I'm Dr. Jessica Bianco from Dalton Animal Care. I'm here with Miss Rosie, one of our heartworm survivors. 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. Let's get started.

How was 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 a 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. Often, we'll recommend chest X-rays to evaluate the heart size and shape and the health of the lungs before proceeding with other treatment.

Is it possible for my dog to have heartworms even if their 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, you 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 they are on year-round prevention?

That's a really good question, and sometimes confusing to answer. The answer is yes, and there's a couple of reasons why. The main reason why is that, unfortunately, no medication or prevention is a hundred percent effective in every situation, and there are 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. 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 to the heart and the lungs 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 the 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. 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 the route that's safe for your dog.

Ask Your Veterinarian About Heartworm Medicine For Dogs

It is important to consult your veterinarian when making preventive care decisions for your dog. This is true for a variety of reasons. There are many over the counter products on the market today that range from ineffective to outright dangerous. Our veterinarians are trained and qualified to help you make the best decisions regarding preventive care and treatment of any health conditions your dog may develop, especially when it comes to parasitic infections.

Featured Quote:

We can stage your dog's heartworm disease to see how severe it is.

Video Transcript:

Dr. Jessica Bianco

Dalton Animal Hospital

 

Hi. I'm Dr. Jessica Bianco from Dalton Animal Care. 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 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. 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 treatment's 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?

Miss Rosie's 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. 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 preventatives.

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. 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?

If we're able to do x-rays and evaluate heart and lungs prior to starting treatment, we can 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. If that happens to you, it's generally around a $1,000 to $1,500 just depending on the size of your dog.

Can I just give my dog their 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. While it may kill the baby heartworms and prevent more adults, you're allowing the adult heartworms that are already in there to continue to cause more damage.

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

If you can imagine, there are big adult heartworms in your dog's heart and towards their lungs, and there are also thousands of baby worms circulating throughout their bloodstream. As we start to kill the baby worms first, and then the adult worms, there's really nowhere for them to go except to die in the bloodstream. As those are moving around and being processed by the body and excreted, your dog is at risk for potential reactions, such as throwing clots to different parts of their body. The more active they are and the higher their blood pressure gets, the more at risk they are for 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. 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. 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 6 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.

Schedule An Appointment To Diagnose Or Prevent Heartworm In Dogs

Heartworm is an easily preventable disease. If your dog is not currently using a veterinarian recommended heartworm prevention medication, please schedule an appointment right away. There is no reason for your dog to be exposed to heartworm disease, when prevention is so simple.

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