What exactly is heartworm?

Tiny round worms are introduced into the bloodstream by infected mosquitoes. They embed themselves in the animal's heart and in the blood vessels of the lungs, where they grow in size up to 15” long and produce offspring called microfilaria. As the worm population increases, the heart must work harder to pump blood. Eventually, the animal will exhibit the symptoms of congestive heart failure, including lethargy, difficulty breathing and coughing. Heartworm disease is a very serious disease and management of the heartworm patient should be taken seriously.

  1. Once diagnosed, x-rays and blood work must be done to stage (see below) the severity of the Heartworms.

  3. Treatment should begin right away. There are two form of treatments that the American Heartworm Society along with many teaching university's and the AVMA recommend.
    1. Standard: Two shot method - 1st shot on day one followed by second shot 24hrs later. Dog should be healthy according to the blood work and xrays.
    2. Alternative: One shot on first day and two shots one month later.
  4. Restrictions: After treatment, the patient must be strictly confined for one month. No running around. The dog must live the indoor life. The reason for this is that embolism (blood Clot) to some degree is inevitable and it is important to minimize embolism-related problems. It would be a good idea to discuss with your vet the possibility of administering one baby aspirin a day which thins the blood and helps minimize embolisms. Remember, the dead heartworms are released through the blood for elimination.
  5. Things to watch for:
    1. coughing
    2. fainting
    3. fever
    4. bloody nose
    These are risk factors which should be reported to your vet immediately.

ACTIVITY: This is a serious risk factor and the only one that you can control. The dog must be kept quiet.

STAGES: Prior to therapy, the heartworm patient is assessed and rated for risk into one of four categories also called stages or grades:

Class I: Lowest Risk.
Young healthy dogs with minimal or no disease evident on x-rays, normal blood work, and no symptoms of illness. They may cough only occasionally if ever, they only fatigue with exercise, and their chest x-ray�s are normal.

Class II: Moderately Affected.
Healthy dogs with minimal signs as above, occasional coughing, fatigue only with exercise but with x-ray�s that show definite evidence of heart disease. Lab testing shows mild anemia, urine dipsticks show some protein present but not severe urinary protein loss.

Class III: Severely Affected.
Dog is suffering from weight loss, cough, difficulty breathing, blatant damage to the vasculature is apparent on x-rays, lab work reveals a more severe anemia and marked urinary protein loss.

Class IV: Caval Syndrome.
Dog is collapsing in shock with dark brown urine evident. Heartworms visible by ultrasound in the AV valve of the right side of the heart, very abnormal blood work. These dogs are dying and can only be saved by the physical removal of adult heartworms via an incision through the jugular vein.


Any treatment plan other than the two listed above will need approval from the Directors.