What Is Heartworm In Dogs?

If you have a canine friend in your life, you should always have the threat of heartworms on your radar.

These blood parasites can be found in every corner of the globe, impacting unsuspecting dogs across the country.

As long as mosquitoes are present in your  region, your dog is at risk of developing heartworms.

In this article we will get into the details of heartworm infections in dogs, and help you better understand how you can protect your pup from these blood-borne critters.

What Is Heartworm In Dogs

What Are Canine Heartworms?

The term heartworm refers to a blood-borne parasite known as Dirofilaria immitis.

These parasites invade the circulatory system in dogs, causing what’s known as heartworm disease in our canine friends.

Once these parasites mature within the bloodstream, the adult worms can invade structures like the heart, lungs, and surrounding blood vessels.

Dogs are a natural host for heartworms, meaning the heartworms can not only thrive within the dog’s body, but also create offspring.

This gives the heartworms an opportunity to truly wreak havoc within the dog’s body, leaving permanent damage to the organs they inhabit.

The Heartworm Life Cycle

Life Cycle of Heartworms in Dogs

The heartworm requires an intermediate host to complete its life cycle.

Without the mosquito, the heartworm would never be able to mature into an adult and produce offspring.

Dozens of species of mosquitoes can be a vector for heartworm, leading to the prevalence of this disease today.

The heartworm life cycle begins when a female mosquito consumes the blood of a dog that is already infected with heartworms.

The immature heartworms are known as microfilariae, and they will further mature in the mosquito’s gut for 10-30 days.

Once the microfilariae have matured, they will then enter the mosquito’s mouth.

Once this occurs, the mosquitos can infect any dog they bite.

When an infected mosquito bites a dog, the microfilariae can then invade the bloodstream.

They will soon make their journey to the heart and the surrounding vessels, allowing them to eventually mature and reproduce.

The maturation process takes approximately 6 months, but once mature, adult heartworms can live up to 7 years within the dog’s body.

How Do Dogs Get Heartworms?

The only way for a dog to become infected with heartworms is through a bite from an infected mosquito.

Once the infected mosquito bites your dog’s skin, the immature heartworms will make their way into the dog’s bloodstream.

Over 30 species of mosquito can carry heartworms, so heartworm infection is a prevalent threat around the world.

Are Heartworms Contagious To Dogs?

Heartworms in dogs are not contagious, so they cannot be transmitted from dog to dog.

A dog must be bitten by an infected mosquito in order to develop heartworm disease, so simply being around a heartworm positive dog is not a risk for other furry friends.

If you have an infected dog in your home, you do not have to worry about them passing heartworm disease onto your other pets.

Are Heartworms Contagious To Humans?

Just as heartworm disease cannot be transmitted from dog to dog, it cannot be spread from dog to human either.

While humans can become infected with heartworms in rare cases, you would still need to be bitten by an infected mosquito for this to occur.

Unlike other parasites that invade our pup’s body, humans cannot get heartworms from dogs.

Where Is Heartworm Disease Commonly Found?

As we mentioned above, heartworms are prevalent in every corner of the globe.

As long as mosquitoes have the ability to thrive in an environment, heartworm disease will continue to be present.

Mosquitos are the vector for this illness, so wherever mosquitos are, heartworm disease is not far behind.

Mosquitoes are most commonly found in climates that are warm during some seasons, near some type of coastline, and have plenty of reservoir animals to feed on.

The hotspots for heartworm disease in America include the states lining the Gulf Coast, as well as areas surrounding the Great Lakes.

Though these are considered hotspots for heartworm disease, it can now be found in most regions throughout the states.

What Happens When A Dog Gets Heartworms?

It can take years for a dog to develop any clinical signs of heartworm disease.

Due to the fact that symptoms may not develop for quite some time, not much will occur initially when a dog becomes infected.

Though there may be no external signs of their disease, there is a complex process occurring within their circulatory system.

From the moment a dog is bitten by an infected mosquito, the microfilaria (baby heartworms) will begin their journey to the heart.

Once they have settled in the heart and the surrounding vessels, they will then begin their maturation process.

The adult heartworms will soon begin to mate, leading to the creation of more circulating microfilariae.

Once adult heartworms settle into the heart and lungs, they can begin to clog the major pathways from the heart.

This makes it more challenging for the organs to receive adequate blood supply, eventually leading to organ malfunction.

The heartworms will eventually invade the lungs in severe cases, leading to life-threatening respiratory complications in addition to their cardiac distress.

Can Dogs Die From Heartworms?

Unfortunately, dogs die from heartworm infections all the time.

Though we tend to only visualize the parasites that invade the heart, there are many ways in which heartworms impact the canine body.

To help you better understand how serious heartworm disease is in dogs, lets list a few of the medical complications they cause below.

  • Inflammation of the blood vessels
  • Inadequate blood flow to organs, especially the lungs, liver, and kidneys
  • Clotting in the lungs
  • Kidney failure
  • Liver failure
  • Lung infections
  • Heart failure

As you can see, a severe heartworm infection can impact virtually every body system in our canine friends.

Heartworms put a significant amount of stress on the body, leading to an array of life-threatening complications to follow.

Symptoms Of Heartworm Disease In Dogs

When discussing heartworm disease in our canine friends, the symptoms will often vary from dog to dog.

A dog’s clinical signs will depend on how long they have been infected, how large their heartworms have become, and which areas of the body are being affected.

To help you better detect the signs of heartworm disease in your pup, lets list some of the most common symptoms below.

Some of the standard signs of heartworm disease in dogs include:

  • Lethargy
  • Weakness
  • Loss of stamina
  • Difficulty catching their breath
  • Disorientation
  • Coughing
  • Weight loss
  • Poor coat health
  • Fainting
  • Pale gums
  • Distended abdomen

If you notice any of the above symptoms in your dog, we suggest reaching out to your vet immediately.

Even if heartworms are not the cause of your dog’s illness, these symptoms can point to other serious medical conditions.

Diagnosing Heartworms In Dogs

In most situations, your vet can diagnose heartworms with a few simple blood tests.

These tests are easily accessible, and can typically be performed in your vet’s office.

First, your vet will likely suggest performing a yearly ELISA heartworm test (snap test).

This is achieved by obtaining a small sample of fresh blood collected from your pup, and applying the sample to a snap test that searches for an antigen released by pregnant female heartworms.

If the test is positive, this suggests that your dog has adult heartworms in their body.

Your vet may also recommend performing a direct blood test to search for microfilaria, especially if your dog has tested positive on their heartworm snap test.

This is the only in-house diagnostic that can confirm the presence of immature heartworms, as the ELISA test only searches for the adult heartworm antigen.

A direct blood test is performed by applying a drop of blood to a slide and examining the sample under a microscope.

If your dog does have heartworms, you will likely see microfilariae moving throughout the sample.

Once your dog has tested positive for heartworms with both a direct test and an ELISA snap test, your vet may recommend performing a full panel of blood work.

Heartworms can lead to irreversible organ damage, so it’s important to assess the level of damage that has already occurred.

While an x-ray is not necessary to confirm a heartworm diagnosis, it is beneficial in determining the best treatment plan for your pup.

A chest radiograph can search for the evidence of heart or lung damage, allowing your vet to tailor their treatment to fit your dog’s needs.

Dogs with heart or lung damage will need to be closely monitored throughout treatment, and may require additional care outside of the normal treatment protocol.

Can You Treat Heartworms In Dogs?

Heartworms can be treated in dogs, but treatment does come with a list of potential risks.

Heartworm treatment will require close monitoring from your veterinarian, as well as strict adherence to any instructions that your vet orders.

A dog’s treatment will also vary based on the severity of their case, as well as whether or not they have any underlying complications from their disease.

Another factor to keep in mind is the fact that many dogs are not diagnosed with heartworms until they have developed clinical signs of their condition.

This always makes treatment a bit more complicated, as this could mean that a dog has had heartworms for years.

The longer the dog has been infected, the higher the chance of secondary complications.

Adult heartworms and microfilariae will need to be addressed in different ways, so there will always be at least two aspects of your dog’s standard treatment plan.

The standard treatment protocol for adult heartworms involves an initial injection with a substance known as melarsomine (immiticide), followed by a 30 day period of rest.

Your vet may also prescribe an antibiotic known as doxycycline during this time period, as this can help to fight any bacteria that is released from the dying heartworms.

If your pup makes it through this period without any complications, they will then receive two more injections that are administered 24 hours apart.

Some veterinarians may even suggest keeping your dog in the hospital for this 48 hour period.

Though every veterinarian has a different preference, most vets will suggest tackling the microfilariae 4-6 weeks after your dog has completed their treatment for adult heartworms.

Your dog will typically stay in the hospital to receive a large dose of ivermectin or something similar, allowing your vet to monitor them closely for any adverse reactions.

Negative side effects will vary based on how many microfilariae are in circulation, with higher numbers increasing the risk of adverse effects.

Once your dog has completed their heartworm treatment, your veterinarian will suggest having them tested for microfilariae within 2-3 weeks.

If they have tested negative at this point, your dog can then be prescribed a monthly heartworm prevention plan going forward.

How Long Will My Dog With Heartworms Need To Stay Calm?

One of the most important aspects of treating your dog for heartworms is the strict rest that needs to come along with it.

As the heartworms begin to die within the first few days of treatment, these worms will soon start the decomposition process.

The dead heartworms will soon be carried into the lungs, lodging themselves into the tiny blood vessels in the area.

It can take weeks to months for the body to absorb the broken up pieces of heartworms, and any stress on the body can complicate this process.

Anytime a dog exerts themselves, they will need to put some extra stress on the heart and lungs.

If a dog has pieces of decomposing heartworms lodged throughout their vessels, any vigorous activity can cause serious damage to these organs.

In fact, most complications that occur during heartworm treatment are a result of dogs not adhering to their rest requirements.

Most veterinarians will recommend that your dog is under strict rest requirements for 60 days.

It can take 6-8 weeks for the heartworms to be absorbed naturally once treatment begins, so you do not want to take any chances when it comes to physical activity.

This is the most challenging aspect of heartworm treatment for most pet owners.

How Long Is Heartworm Treatment?

The length of a dog’s heartworm treatment will vary from case to case.

Most dogs will complete their treatment within an 8 week period, but some will need to undergo multiple rounds of treatment if they still test positive afterward.

If you would like to have an accurate idea of how long your dog’s heartworm treatment will be, we suggest speaking with your veterinarian.

Heartworm Treatment Complications

With any condition that has the ability to impact multiple body systems, there are always risks involved with treatment.

The fact that most dogs are diagnosed with advanced stages of heartworms only makes it more complicated, as many of these pups have already sustained some form of organ damage.

Most dogs will have a smooth recovery when following their vet’s guidance, but there are some signs of brewing complications that you should always be aware of.

Some of the most common symptoms of heartworm treatment complications include:

  • Coughing
  • Weakness
  • Anorexia
  • Fainting
  • Ataxia
  • Limb weakness
  • Labored breathing

If you notice any of the above symptoms or any other significant changes in behavior, we suggest reaching out to your veterinarian immediately.

Can You Prevent Heartworms In Dogs?

Thankfully, there are many affordable options available to prevent heartworms in your canine friend.

Whether your pup has been treated for heartworms or not, they will need a monthly prevention that bans these blood-borne critters for good.

Just ask your veterinarian about the best preventative options for your dog, and they can point you in the right direction to fit your needs.

Final Thoughts

Heartworm disease is a complicated, yet preventable medical condition in our canine companions.

No matter where you and your pup live in the world, the threat of heartworms should always be on your radar!

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