How Do Dogs Get Heartworm

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How Do Dogs Get Heartworm

January 25, 2023 6 min read

While most people know that dogs can get tick-borne illnesses such as Lyme disease and canine hookworms, few are aware that they may also be at risk for something more serious: heart worm!

What is it?

Heart worms are actually nematode parasites that live in the blood vessels of animals. They are typically spread when an infected dog bites or licks its own skin or those of other dogs, ingesting microfilariae, the larvae stage of the parasite.

The next step is for these larvae to develop into adult worms within the bloodstream. Adult females produce offspring called “microfilaria” every 30 days or so, parasitizing additional cells along the way. If this happens enough times, the parasite will eventually mature and become clinically significant.

Most commonly seen in sub-tropical and tropical areas, the species of heart worm that infects both cats and dogs is Dirofuronema brunnianum. This parasite was first discovered in Peru in 1935 and now is found almost exclusively in regions with warm climates and poor sanitation.

Canine heartworm is commonly referred to as a “dreaded” disease because of its severe symptoms and potential complications.

how dog get heartworm

While most dogs never show any signs or symptoms of heartworm, it is important to be aware that there are several different stages of this disease.

A dog in either an advanced stage or early stage can experience sudden cardiac arrest due to possible development of heartworms. This happens when enough parasites migrate through the blood and into the heart tissue where they grow and reproduce.

If a dog is experiencing such symptoms at around one month after being exposed to heartworm, appropriate testing and treatments will need to occur immediately.

Sudden death is very serious event for your pet and should always be addressed right away! Fortunately, there are ways to prevent exposure to heartworm by knowing how to identify risk factors, determine if your dog has heartworm already, and manage treatment if necessary.

The first step in identifying heartworm is a blood test.

A Dog Having a Checkup on a Veterinary

Photo by Mikhail Nilov onPexels

A red flag for heartworm disease is when your dog has symptoms of breathing difficulty, lethargy or other cardiovascular problems such as light-headedness or dizziness.

These signs can be the result of another condition so it is important to rule out other conditions before assuming that your dog has heartworm.

It is also important to note that although most dogs are exposed to heartworms once they have been diagnosed with heartworm disease, some individuals are immune or don’t develop heartworm because of this.

So even if your dog has heartworm, he may not need treatment unless you want to prevent further issues from occurring. Fortunately, there are ways to do this!

Fortunately, there are good treatments available for dogs who have been diagnosed with heartworm. These include monthly pills or injections that contain either an antiparasitic drug or corticosteroid to reduce inflammation.

If heartworm is present, the next step is to determine the severity of the infection.


Photo by Brett Sayles onPexels

There are two different ways that veterinarians assess the risk of heartworm in an animal. The first is through blood tests, which look for specific antigens associated with heartworms. These can be done either via blood or fluid (urine) samples, depending upon what body part is being tested.

The second way to check for heartworm is by performing a complete physical exam. This includes looking at all of the patient’s external body parts like their paws and fur, as well as examining their internal organs.

If your dog has been diagnosed with heartworm disease, then there is help available! Veterinary medical professionals may be able to administer a medication called ivermectin, which kills off any existing heartworms your dog might have.

Heartworm can be present without any symptoms or with mild symptoms.

how dog get heartworm

Although most dogs do not need to be tested for heartworms, there are some situations where testing is needed to confirm the diagnosis or rule out possible infection.

For example, if your dog has been diagnosed with parvovirus (distemper) then they must also have a test for heartworms. Or if your dog develops sudden weight gain or feels very tired and weak, then you should consider having a heartworm test.

However, even though these tests are helpful in confirming an existing heartworm disease or ruling one out, they cannot determine whether a newly found heartworm parasite will develop into a mature adult worm. This happens when the worms find a suitable place to live in the host’s body.

It may take months or years before this occurs, so it is important to prevent heartworm by ensuring that your home and outdoor areas are safe for your pet. Also, make sure to give your animal enough food, water, and exercise to keep them healthy!

Once again, since heartworm is spread through bites from infected insects, protecting yourself and your family from mosquitoes is essential in preventing heartworm. You can learn more about how to protect yourself here.

This article was written by Katrina from The Healthy Pet Company. For more information on smart products for pets, visit

Heartworm can be present in different areas of the body, including the brain, spinal cord, and lungs.


Most dogs are exposed to heartworms for just a few weeks at a time when they play in an area with infected mosquitoes or when they ingest mosquito feces containing larvae.

However, some puppies and adult dogs may become persistent “susceptibles” because their immune systems aren’t strong yet. They develop antibodies that help protect them from similar infections in future years, but if those disappear then it makes it easier for the parasite to take over.

Infestations usually don’t cause any symptoms until many months later when patients experience shortness of breath, weight loss, fever, vomiting, diarrhea, and other flu-like signs and symptoms.

Heartworm can be present without any symptoms for many years before any symptoms appear.

how dog get heartworm

Although most dogs are resistant to heartworms, it is important to know how to identify heartworm disease in order to recognize the signs of this deadly condition. If your dog has been exposed to an infected animal or if his immune system is weak due to other health conditions, then it is possible for him to get sick from heartworms!

If you notice changes in your dog’s behavior such as sleeping more than usual, acting nervous or agitated, refusing to eat or drink, having chest pain when he exercises, weight loss, and/or slow breathing, take him to the vet right away.

Heartworm can cause serious complications including heart damage and even death.

how dog get heartworm

While most dogs never need treatment for heartworm, some do. For these dogs, their immune systems are strong enough to fight off the disease but it flares up at times.

When this happens, sometimes heartworms get into other parts of the body where they don’t belong.

These extra parasites could hurt you or your dog!

Symptoms include fever, vomiting, weight loss, sluggishness or fatigue, breathing problems (dyspnea), dark red skin that may bruise easily, swollen eyelids and/or face, coughing, seizures, and more.

If you think your dog has heartworm, call your veterinarian right away so we can help him or her deal with this health challenge as best we can.

Dog owners should be aware of how to tell if their dogs have heartworm by looking for symptoms and seeking veterinary care early.

Heartworm is a contagious disease that is spread through the bite of an infected mosquito.

how dog get heartworm

There are two types of heartworms — juvenile or fetal, and adult stage. The most common type is the larval form, which means it’s in the form of larvae. These immature worms develop within your dog’s body for about one month before they enter the bloodstream as first-stage parasites (microfilariae).

The microfilariae then travel to your dogs lungs where they mature into second-stage parasites. At this stage, they can be seen moving across the tissue under a microscope. This is when symptoms begin to show up.

Dog owners usually notice changes in behavior and activity level, but other symptoms may go unnoticed. Some of these include weight loss, coughing, lethargy, and difficulty breathing. If you notice any of these signs in your dog, see your vet right away!

Fortunately, there are some ways to prevent heartworm in dogs. Vaccinating your puppy against heartworm at six weeks old and again at twelve months will help make sure he is protected until his immune system matures fully. For more information, talk with your veterinarian.

He also suggests doing regular checks for mosquitoes around your home so that you can take action if needed. Using appropriate insect repellent during outdoor activities will also reduce exposure.

Cindy PetsForLife
Cindy PetsForLife

Hello, I'm Cindy, the founder of PetsForLife. I am a true animal lover with 3 cats and 1 dog of my own. My passion for all things pets has led me to create a unique collection of personalized pet gifts. Check out our personalized pet gifts on our website.

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