Canine heartworm disease is caused by the worm Dirofilaria immitisthat lives in the blood vessels leading from the heart to the lungs. The presence of these worms causes strain to the heart and an intense reaction in the blood vessels. This parasite is transmitted by mosquitoes. For this reason, heartworm disease is more common in warm, humid areas of the world.

Outdoor dogs are predisposed and male dogs may be more likely to develop infection than females. The most important predisposing factor is failure to receive heartworm preventative medication. All dogs living in an area where heartworm disease exists are at risk, even if they live entirely indoors.

Impact on the pet is variable. Dogs can be without symptoms if the infection is light or has occurred recently. In some cases, heartworm disease can cause severe debilitation and eventually may be fatal.

Diagnosis and Treatment Notes:

  • Heartworm disease is generally diagnosed by physical examination and blood tests. Chest x-rays, electrocardiogram (EKG) and blood work are done to determine the severity of the disease. Sometimes, an ultrasound of the heart (echocardiogram) is recommended.
  • Treatment depends on the severity of the disease, your individual pet, and your veterinarian. Heartworms are treated in stages. The adult worms are most commonly killed with melarsomine. After a short period of time, the baby heartworms are then killed with a different medication. Discuss treatment details when your pet is diagnosed with this condition.
  • Prevention: Prevention of heartworm disease should be undertaken in all dogs. These include monthly and daily preventatives.


What to Watch for*:

  • Coughing (sometimes with blood)
  • Heavy breathing
  • Unwillingness to exercise
  • Collapse
  • Signs of right sided congestive heart failure, which includes fluid distention of the belly

*Please notify us if you notice any of the above signs or if you have any questions!