How to Check if Your Dog Has Heartworms?

How to Check if Your Dog Has Heartworms

How to Check if Your Dog Has Heartworms?- Mosquitoes act as an intermediate host while one of the definitive hosts of heartworm in dogs means they grow, mature, and multiply in dogs.

Here’s a breakdown of how to check for heartworms in dogs, what happens if they’re infected, prevention tips, and key takeaways:

What are Heartworms?

  • Parasitic roundworms (Dirofilaria immitis) living in the heart, lungs, and blood vessels of infected dogs.
  • Spread by mosquitoes that bite infected dogs and then transmit heartworm larvae to other dogs.
  • Can be fatal if left untreated.

Symptoms of Heartworm Disease

  • Early-Stage:
    • Decreased appetite and weight loss
    • Persistent cough
    • Laziness
  • Late-Stage
    • Bulging ribs
    • Difficulty breathing
    • Collapsing and fainting

Important: These symptoms can indicate other health issues, so a vet checkup is essential for a definitive diagnosis.

When to Test for Heartworms

  • Puppies: Start heartworm prevention medication and testing after 6 months.
  • Adult Dogs: Annual heartworm testing.
  • Missed Tests: Consult your vet for appropriate testing intervals.

How to Check for Heartworms

  • Vet Visit: Your veterinarian will perform the following tests:
    • Antigen Test: Detects proteins from adult female heartworms, indicating infection.
    • Microfilariae Detection Test: Confirms infection if heartworm offspring are found in the bloodstream.

What to Do if Your Dog Tests Positive

  1. Confirm Diagnosis: Your vet may perform additional tests for certainty.
  2. Restrict Activity: Limit your dog’s exercise to minimize strain on their infected heart and lungs.
  3. Treatment:
    • FDA-approved medications are used to kill both adult heartworms and their offspring.
    • Treatment cost can be high (approximately $1000 or more) depending on severity.
  4. Side Effects: Treatment can have toxic side effects, so your vet will closely monitor your dog.

Heartworm Treatment Success Rate

  • Modern medications have a success rate above 95%.

Prevention is Key

  • Vet Consultation: Discuss the best preventive measure for your dog.
  • FDA-Approved Medications: Monthly oral or topical medications, or long-lasting injections, are available for protection.
  • Annual Testing: Even with preventative measures, yearly tests are recommended.

Key Takeaways

  • Heartworms Are Serious: This disease can be fatal if untreated.
  • Early Detection is Crucial: Symptoms might not appear until the disease is advanced.
  • Prevention Is Best: Work with your vet to protect your dog.
  • Regular Testing is Essential: Ensures your dog stays healthy and catches any infection early.

Remember: With awareness, prevention, and timely veterinary care, you can protect your dog from the dangers of heartworm and ensure a long and healthy life.

How Do Heartworms Enter a Dog’s Body? What is a Heartworm’s Life Cycle?

Heartworm completes its life cycle in 2 hosts: mosquito, which acts as the intermediate host, and dogs, the definitive host.

  • In an infected dog, heartworm releases its offspring, known as microfilariae, into the dog’s bloodstream. The life cycle of Dirofilaria immitis (heartworm) begins when a female mosquito bites a dog that is already infected with heartworm.
  • The mosquito then becomes infected with microfilariae.
  • The offspring (microfilariae) becomes infective larva while living inside a mosquito for the next 10-15 days, the offspring (microfilariae) becomes infective larva.
  • When these mosquitoes (who carry infective larva) bite another dog, the infective larva enters the dog’s body.
  • It roughly takes 6 to 7 months for this infective larva to become a mature adult.
  • Then these adult roundworms mate and release their offspring (microfilariae) into the bloodstream of the infected dog.
  • And when any mosquito bites this infected dog, it will become infected with microfilariae. And so, the life cycle of heartworm completes in this way.

Symptoms of Heartworm Disease

The type of symptoms shown by the dog depends on which stage the parasite is present.

Early-Stage Symptoms

Decreased Appetite and Weight Loss

The parasite withdraws energy from dogs’ bodies when they begin to spread in a dog’s body. A simple task like eating food will be exhausting for dogs because of low or no energy. And this results in weight loss in them.

Persistent Cough

Early infection of heartworms causes dry and persistent cough in dogs.


If your dog suddenly stops playing and going on walks and sits or sleeps all day, it can be a sign of roundworm.

Late-Stage Symptoms

Bulging Ribs

Because of weight loss, the dog’s ribs will have a Bulging appearance. Bulging Ribs can also be caused by fluid buildup in the lungs in response to the parasite’s presence.

Difficulty in Breathing

Because of persistent coughs, dogs may start feeling difficulty in breathing.

Collapsing and Fainting

Once the roundworm cause caval or vena cava syndrome (blockage of blood flow), fainting will frequently occur in dogs.

Also, if Red blood cells start decreasing at a high rate, collapsing happens in dogs. This is the stage where the infection has already been done in the dog’s whole body, and death may occur within a few days.

Just remember these symptoms can be a sign of other conditions. So before jumping to any conclusion, take your dog to your vet for a proper checkup.

When Should Dogs Be Tested for Heartworms?

As a part of preventive measures, it is advised for regular checkups of dogs for heartworm.

  • Below the age of 6 months, puppies can receive their heartworm prevention medication. Then again, take your dog after six months for a heartworm test and regularly for the test once a year. It guarantees your dog is negative for heartworm.
  • If somehow your dog misses its test against roundworm, take him immediately to the vet and then go after six months. The six-month duration between two tests is because it takes at least six months to show positive for roundworm after being infected.

How to Check if Your dog has Heartworms?

To confirm if your dog is suffering from heartworm disease or not, your dog has to undergo some tests.

Antigen Test

The vet will do a blood test and antigen test to check your dog for heartworms. The presence of a special protein released by adult female heartworms in a dog’s bloodstream confirms that your dog has been infected by roundworm disease.

This special parasitic protein can be detected by antigen test. This protein shows five months after the dog is infected. This antigen test accurately detects the infection in dogs.

Microfilariae Detection Test

Microfilariae in the offspring of adult roundworm and its presence in dogs confirm roundworm infection in dogs.

These microfilariae are present in the bloodstream of dogs. And if a blood test shows the presence of microfilariae, then your dog is infected with a roundworm parasite.

What Should Be Done When Your Dog Tests Positive for Heartworm?

Dogs are prone to many dangerous diseases, and heartworms are one of them. Heartworm is a parasitic roundworm caused by Dirofilaria immitis spread through the bites of mosquitoes from host to host.

Symptoms of heartworm will start showing up post six months of infection. And if your dog is showing symptoms of roundworm, it means the disease has already been spread in his body.

Confirm the Diagnosis

If your dog has tested positive for heartworm, then go ahead for a diagnosis to confirm with an additional and different test. It is so because the treatment is expensive, so be sure of this.

Restrict Your Dog’s Activity

Try to restrict your dog’s physical activity to a bare minimum. Allow only minimal walk for bodily functions like urinating and defecating only.

How Much Does it Cost to Treat Heartworm Disease in Dogs?

Treating heartworm disease can be quite expensive as well as exhausting. Dr. Muller has said that “The pure treatment of roundworm disease might be around $500, but a complete examination and treatment (including X-rays, blood tests, and proper follow-up testing) might add up to $1,000 or more.”

The cost of heartworm disease also depends upon the severity of the disease, location, and at which stage the dog is present.

Can Heartworm Disease Be Cured?

Yes, most heartworm disease cases in dogs are curable.

  • An FDA-approved drug Melarsomine dihydrochloride (arsenic-containing drug), kills adult roundworms in dogs. This drug is given by deep injection into the dog’s back muscles. It is used to treat dogs with class 1, 2, and 3 roundworm disease.
  • Another FDA-approved drug, imidacloprid, and moxidectin, is used to get rid of microfilariae (offspring of adult roundworm) in the dog’s bloodstream.

What is the Survival Rate of Heartworm in Dogs?

Earlier, the drugs which are used to treat heartworms had high levels of arsenic which caused toxic side effects. The new drugs that have come on the market for treatment have increased the success rate of heartworm treatment in dogs. The success rate is more than 95% treatment of dogs with heartworm.

What are the Side Effects on Your Dog’s Body?

Roundworm disease treatment can be toxic to your dog’s body. Potential side effects on your dog’s body are blood clots in the dog’s lungs.

How to Prevent Your Dog from Getting Infected with Roundworm?

Dr. Choczynski suggests long-lasting injection or oral medication in dogs that sometimes include flea and tick prevention.

  • Many FDA-approved drugs are present in the market to be given on a monthly basis to prevent dogs from heartworms. These drugs can be given orally or as a topical liquid applied to the skin.
  • Talk to your vet to know which measure is best for your dog to protect him from this deadly disease.
  • You can also give your dog 12 months of heartworm prevention and get him tested every 12 months for heartworms. This prevention has been suggested by AMERICAN HEARTWORM SOCIETY.

Every breed of dog is prone to roundworm infection. And the best way to protect your dog from getting infected is through prevention. Follow the above-given measures to protect your dog from catching roundworm infection.

But how to check if your dog has heartworms? Despite all prevention, if you find your dog to have any symptoms of roundworm, take him to the vet immediately.

Aapt Dubey
Aapt Dubey

Aapt Dubey, a devoted canine enthusiast and experienced dog Owner, brings boundless passion to our team. With a heart full of love for our four-legged friends, Aapt is dedicated to sharing insights on dog care, behavior, and training to make every pup's life happier and healthier at

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