Common Heartworm Symptoms in Dogs

Adult heartworms from dog's heart

Heartworm (also known as Dirofilariasis) signs can take months to appear. Here are some of the common signs that a canine may have heartworms.

In areas where Dirofilaria immitis is endemic, dogs without appropriate heartworm protection are highly likely to develop heartworm disease. The heartworm is generally endemic in geographical locations with tropical and subtropical climates. It is typically discovered along the Atlantic and Gulf Coasts, and the Ohio and Mississippi river basins. The existence of Dirofilaria immitis is not restricted to these locations, nevertheless. It is found worldwide. Dogs have been diagnosed with heartworm disease in all 50 U.S. states.

Heartworm disease in dogs is a silent killer that is frequently ignored up until it’s far too late. This preventable condition starts with a mosquito bite and ends with either a long, costly treatment or death.

Symptoms may not appear till the worm reaches maturity (normally after around 6 months).

Heartworm Symptoms in Dogs

1. A soft, dry cough
The parasites make their method to the lungs and start increasing in the lungs and surrounding veins. Coughing might be most visible after workout and may end with fainting. Even light exercise can trigger fainting.

2. Inactivity or lethargy
Your pet unexpectedly appears tired more frequently, doesn’t wish to go outside, or avoids all physical activity. Pets with heartworm infection are deteriorated and discover it challenging to be active even when performing little tasks.

3. Weight-loss or anorexia
Even small exercises, such as consuming, can end up being challenging and stressful tasks.

4. Fast or challenging breathing
Together with coughing, breathing issues happen when the worms inhabit the lungs and surrounding veins. Fluid can also construct around the blood vessels in the lungs, making it hard for the lungs to oxygenate the blood.

5. Bulging chest
The ribs might appear to protrude, and the chest has a bulging look as an outcome of adult heartworm infection. This symptom can arise from weight loss and anorexia caused by heartworms. This can also be brought on by fluid accumulation in reaction to the parasite’s existence.

6. Allergy
Although allergic reaction is more common in felines, it is possible for pet dogs to show symptoms much like an allergy or asthmatic signs in action to the heartworms or their offspring.

7. Collapse
Large numbers of heartworms attack the heart and trigger blockage of blood circulation (called caval or vena cava syndrome). Collapse is generally accompanied by shock and red blood cell damage. Death can follow within days.

Other heartworm symptoms are possible, too:

  • Nosebleeds
  • Secondary pneumonia
  • Increased blood pressure
  • Extreme sleeping
  • Seizures
  • Loss of sight
  • Lameness

Seizures, lameness and blindness take place when the parasites get lost and wind up in places aside from the heart or lungs. They can end up in the brain or eyes, although this is uncommon.

A few of the symptoms above can also be indications of other conditions, makings it more difficult to identify heartworm infection. There are other tools utilized by veterinarians to discover the condition more precisely.


Blood tests to spot the different stages of infection can include viewing a blood sample under a microscope and examining for antigens of adult heartworms (a protein the heartworms produce as well as the most frequently used test, inning accordance with VCA Animal Hospitals).

Other blood tests can look for abnormalities in complete blood counts and evaluate the level of function of the internal organs.

  • Radiographs (X-rays) might detect inflammation, augmentation, or swelling of the heart, lungs and the big artery leading to the lungs from the heart (lung artery).
  • Irregular heart rhythms and enlarged heart chambers can be spotted by an electrocardiogram.
  • An ultrasound of the heart (echocardiography) can help figure out the health of the heart for treatment and provide a visual of any existing heartworms.

These tests are also utilized to determine the health status of the internal organs. This is needed to assess whether the canine is healthy enough for treatment.

Treatment for Heartworms in Dogs

Heartworm treatment for any dog starts by removing the adult roundworms and takes about 1 month to complete. The dead adult worms are then absorbed by the body.

After this stage, the next treatment eliminates the more youthful parasites and offspring. In severe cases, surgical elimination of heartworms from the internal organs might be required.

This condition is avoidable. If your pet is not taking a heartworm preventive, please talk with your vet about beginning.

Reyus Mammadli
Having engineering and medical education, in recent years actively engaged in the study of the development, reproduction of domestic animals. Special attention is paid to the treatment and prevention of diseases of Pets.
Pet Health
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