How Dogs Get Heartworm: A Complete Insight

how do dogs get heartworm

People always ask how dogs get heartworm and in this article, we will be discussing the two primary ways dogs get heartworm, you will also find out the symptoms and prevention of heartworms in this article.

Heartworm disease is a serious canine illness that, if left untreated, can be fatal. It is caused by the parasitic worm Dirofilaria immitis.

Heartworm disease is a growing problem in the US.

It’s estimated that more than 600,000 dogs are infected with heartworm each year, and close to half of these cases go undetected.

So, How Dogs Get Heartworm

Heartworms are transmitted to dogs through two major routes: through an infected mosquito bite or the consumption of Dirofilaria immitis-infected meat or food.

Heartworm infection causes severe lung illness, heart failure, other organ damage, and death in dogs.

Dogs become infected with heartworm when they are bitten by mosquitoes carrying the parasite.

First discovered in the United States in 1944, heartworm has now spread to most of North America and parts of Europe.

A dog’s risk of contracting heartworm disease depends on where you live and what type of mosquito carriers are prevalent in your area.

Signs of Heartworm in dogs

Here are some common symptoms or signs of heartworms in dogs;

  • Mild persistent cough
  • Reluctance to exercise
  • Muscle tremors
  • Fatigue after moderate activity
  • Fainting
  • Frequent loss of appetite
  • Breathing difficulty
  • Too much drooling
  • Lethargy
  • Jaundice
  • Lower energy levels
  • Rapid weight loss

It’s question time, so let’s try and answer some of your questions;

What are the first signs of heartworms in dogs?

Reduced appetite, aversion to activity, tiredness, coughing, rapid weight loss, and eventually heart failure are early indications of heartworm infection in dogs.

As the heartworm illness advances, dogs may suffer heart failure and a bloated belly from the accumulation of fluid in the abdomen.

Can heartworms in dogs be cured?

Yes, heartworms in dogs can be cured by first stabilizing the dog, and giving treatments that will kill the adult and immature worms while keeping the side effects of treatment to a minimum.

However, treatments can be a bit expensive and can last longer than you expected. Always check with reputable vet specialists.

Do dogs poop out heartworms?

No, dogs cannot pass heartworms through feces therefore, heartworms cannot be passed directly from one host to another, it requires mosquitoes to transfer the heartworm larva.

The Four Stages Of Heartworms In Dogs

Here are the four basic stages of heartworm in dogs:

Stage one

The initial stage of heartworm infection in dogs is usually symptom-free.

Heartworms are present and settle inside the heart at this time.

However, the illness has not advanced to the point where the heartworms have formed a new generation of microfilariae and the dog’s body has produced antigens in sufficient amounts to be detected.

Stage two

Heartworms in dogs at this stage are characterized by mild symptoms such as resistance to activity and a persistent cough.

At this stage, the heartworms have been resident in the body long enough to produce antibodies and possibly microfilariae.

During this time, blood tests may be used to identify heartworm disease.

Stage three

In the third stage, the spread of the disease symptoms will be obvious and have a significant influence on the dog’s health.

Dogs will experience much coughing and exhaustion will persist after any activity, and dogs may be hesitant to exercise at all.

The dog may also have respiratory problems, most of the time the dog may also cough up blood at this time.

On x-rays, the heartworms are visible at this stage, and the worms in the heart and major vessels are also visible.

Stage four

Heartworm disease symptoms in dogs at this stage are quite evident.

These symptoms are accompanied by long-term health consequences for the dog.

The dog will be in a critical condition and will be hesitant to exercise, will be weary afterward, and will cough.

The dog will have difficulties breathing as well as abnormal noises in the dog’s heart and lungs, as well as an enlarged liver, which may indicate the disease’s impact during testing.

Even with therapy, there is a substantial chance of long-term debilitation and mortality at this stage of the disease.

What are the final stages of heartworms in dogs?

The final stages of heartworms in dogs are the adult stages of the heartworm which take 6 months and the heartworm can live for 5 to 6 years of the lifecycle.

During the final stages, there will be abnormal sounds in the dog’s heart and lungs, as well as an enlarged liver, which might indicate the disease’s impact.

Even with treatment, there is a significant risk of long-term disability and death at this stage of the disease.

How can you prevent heartworms in dogs?

Here are some ways to help prevent your dog from getting heartworm.

  • Your dog should not go outside after dark.
  • Create a barrier between your yard and the rest of the neighborhood.
  • Keep the grass mowed.
  • Limit access to crawl spaces under porches.
  • Keep out long-standing water in buckets, gutters, birdbaths, and wheelbarrows.
  • Make sure your pet yards are cleaned every week and check under vehicles, where mosquitoes may be laying eggs.
  • Maintain a high-quality flea and tick prevention product on your pet for two to three months.
  • Take your pets for a bath regularly, use the right flea collar, and keep your pet inside.

What type of mosquitoes transmit Heartworm to dogs

The mosquitoes Aedes, Anopheles, and Mansonia are all capable of spreading or transmitting heartworm to dogs.

Mosquitoes transmit heartworm by biting an infected host and then passing the parasite to another host during a blood meal.

How do mosquitoes transmit Heartworm to a dog?

Heartworm is a parasite that can be transmitted to dogs through mosquito bites.

When an infected mosquito bites a dog, the mosquito leaves a wound on the skin of the dog and then passes on microfilaria by creating a path for infective larvae to enter their new host and continue their lifecycle in the dog’s bloodstream.

The worm’s larvae are spread through the blood flow and grow into mature worms inside the dog’s heart and lungs.

The most common way a dog comes in contact with heartworm is by being bitten by an infected mosquito.

It can also be transmitted if the dog eats an animal that already has the worm, or if it gets infected by its mother who had been bitten before giving birth to her pups.

What are the different types of heartworm carried by mosquitoes?

Despite having a similar name, heartworm disease is not found in just dogs. There are two types of heartworm disease in dogs:


‘Heartworm-positive’ refers to the dog’s body being infected with heartworm parasites, which can be picked up through mosquito bites.

Dogs can get heartworm disease from one of two places: by being bitten by a mosquito, or when they’ve eaten an infected piece of meat.

Dogs are vaccinated against heartworm, but in countries where the risk of bites is high, the virus often evades these vaccinations

‘Heartworm-positive’ animals are put to sleep because of their poor prognosis, and it is thought that between 40 and 70 percent of dogs euthanized in the US for heartworm have only been infected with the heartworm-negative species.


‘Heartworm-negative’ refers to a dog being infected with a different species of heartworm, but not having any symptoms.

In other words, heartworm-positive dogs are the most likely to die of heartworm, but with the rarest type of heartworm-negative dog in the UK, it’s likely that most of them will still develop heartworm.

Unfortunately, most dogs in the UK have been vaccinated against heartworm, which means they can’t get the virus anyway.

But if they’re bitten by a mosquito, have eaten contaminated meat containing the virus, or maybe even because of a stray dog’s heartworm infection, they can get the virus.

As a result of eating an infected meal, dogs can start to show signs of the disease within two weeks.

Dogs can’t contract the same kind of heartworm that affects humans in the US (the disease which causes ‘Africa Fever’) but a dog can have a heartworm parasite in his or her heart and get heartworm disease as a result.

Animals who survive heartworm disease are often left incontinent, as the disease causes the dog’s heart muscles to get flabby.

They can also develop a wasting disease, which means that their muscles get ‘shrunken’, and eventually, the heart will shut down, causing it to stop pumping blood.

Case Studies of Dog & Heartworm

With a million dogs dying in shelters in 2017, it’s been reported that thousands more are put to sleep every week.

New figures released today by the Dogs Trust, which runs 600 rescued dogs in its care, reveal that a staggering 850,000 dogs are being put down due to health problems each year, compared to a death rate of just 43,000 over the same period in 2016.

It’s hard to say exactly why this is happening, but dogs have a higher risk of getting heartworm disease in the US than in the UK and are often put down in the UK because of a lack of funding for treatment.

But we spoke to Dr. Laura Aarts, senior Veterinary Nurse for Dogs Trust, about the dangers of heartworm disease in the US and why it could easily happen in the US.

Here’s what you need to know…

Heartworms are found in a number of different dog breeds – not just pit bulls

Heartworm disease can be caused by the Heartworm Virus, which affects both dogs and humans.

It’s time for questions and answers!!!

How long will it take a dog to start showing symptoms of heartworms

On average a dog will show symptoms of heartworm disease after 2 weeks of being infected by an infected mosquito or after consumption of heartworm larva by eating infected meat.

How long will it take for a heartworm larva to grow to adult stages

When a healthy dog is bitten by an infected mosquito and the larva is transmitted to the dog, it takes 6 months for the larva to develop into an adult.

During this period a lot of internal organs are damaged.

What’s the outlook for dogs who have been infected with heartworm?

‘Because heartworm-positive dogs are highly prone to premature heart failure and usually die within one to three months,’ Dr. Aarts said.

Dogs with parasitic worms in their hearts are more susceptible to conditions such as anemia and an enlarged heart.

These dogs are put to sleep, and it’s often because it’s a difficult decision for their owners to make, and they don’t want their dogs to suffer.

However, while heartworm infections will not kill dogs, most vets don’t see it as a good reason to put a dog down.

The outlook of an infected dog is always bad and dogs with untreated heartworms are always looking very bad like a homeless dog.

Are there any vaccinations that can prevent dogs from getting heartworm?

‘The best way to prevent heartworm in dogs is to vaccinate them against heartworm,’ Dr. Aarts said.

However, dogs in the UK have never been vaccinated against heartworm, and only a small percentage of dogs in the US get a heartworm vaccine.

According to Dr. Standerwick, there isn’t much evidence that these vaccines are effective at reducing the risk of heartworm in dogs.

But the fact that dogs are not being vaccinated means that vets do not treat heartworm-positive dogs in the UK, which could be an issue if heartworm is detected by blood tests in a vet clinic.

Dr. Aarts says this is why it’s important to get dogs treated for heartworm, as they do provide protection against the parasite.

Is there a blood test to tell if a dog has heartworm?

Dr. Aarts said that it isn’t possible to test for heartworm with a blood test, and it’s up to the vet to diagnose the disease.

When I asked Dr. Standerwick about this, she said that heartworm tests don’t often look for the parasite because the eggs are tiny, and the parasites tend to be resistant to the chemicals that the blood test tests.

‘Some blood tests look for antibodies to the parasite, but the testing isn’t specifically for heartworm,’ she said.

‘A blood test can pick up any disease in the animal, but it won’t be specific to heartworm.’

She said that if a dog is not tested for heartworm, the only way to make a clear decision is to treat the dog for heartworm.

‘If you can’t treat them because they’re heartworm negative, then you’re not doing your job properly,’ she said.

Read more about the causes and symptoms of obesity in dogs.

How can I protect my dog from heartworm?

Unfortunately, the main way to avoid the spread of heartworm is to treat any dogs you plan on adopting.

Although it’s unlikely that the dogs you find on websites or rescue pages have been treated for heartworm if they do, you will not be transferring the infection.

The best way to stop dogs from getting heartworms is to treat any dog you adopt, says Dr. Aarts.

Dogs should also be kept on a leash or indoors and should not roam freely or go for walks too far because that’s where they’re most likely to come into contact with mosquitoes.

When a dog has the infection, the body produces antibodies to fight the parasite, which stops it from infecting the dog again.

Because dogs can’t reproduce, the antibodies pass on the infection to other dogs.

However, Dr. Standerwick said that dogs can develop resistance to antibodies, so if you’ve previously treated a dog for heartworm, you should do it again.

What locations have the highest risk of heartworm in the U.S.?

Heartworm is very rare in the Phoenix area, but are more common in Central Arizona, U.S., where the mosquito population is high.

Heartworm is a type of mosquito-borne infection that spreads to your pet from an infected mosquito bite.

For instance, dogs living in warmer climates like southern Florida have a higher risk than those living in more northern states like Canada or New York.

There are many reasons your dog may have gotten heartworm, but the most common is when you’re in a community where there are infected mosquitoes.

Heartworm is a fatal disease, and it kills dogs. The most common cause of death is fluid in the lungs.

That’s why preventing a dog’s exposure to infected mosquitoes is so important.

Conclusion On How Dogs Get Heartworm

Dogs get heartworms from mosquitoes. This is because heartworm larvae, which are transmitted by mosquito bites, travel to the dog’s lungs and then to the heart and pulmonary arteries.

Dogs with heartworm disease can have difficulty breathing or coughing, they may feel lethargic, lose weight, and show signs of anemia such as weakness or pale gums.

Diagnosis is usually done through a blood test. If your dog is showing any of these symptoms you should take them to the vet for a checkup.

Any potential heartworm cases should be reported to your local animal control department so that they can get treatment for the infected dogs and prevent the spread of heartworm disease.

It’s also important to vaccinate your dog for heartworm. A canine heartworm vaccine is available in most pharmacies.

In final words, the best method of treating heartworms is to prevent them by keeping your dog away from the reach of mosquitoes.

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