Heartworm Disease- Prevention Is the Key

It is safer and much less expensive to prevent the disease rather than to treat it.

Heartworm is a serious infestation that affects both dogs and cats. Summer is the peak season for heartworms because mosquitoes are the transmitters. There are no approved drugs for treating heartworms in cats. That makes prevention vital!

It’s that time of year to visit or call us for details on what the parasite (fleas, ticks, roundworms, heartworm) situation is in our area. We can direct you to which screenings or preventive treatments that are best for your pet.

New customers? call for your 50% Discount on your initial consultation today 408-996-1411. Existing clients ask about our Annual Care Checkup Special.


Symptoms of heartworm disease may include loss of appetite, exercise intolerance, lethargy, weight loss, fever, difficult, labored breathing, shortness of breath, weakness, coughing, dull dry coat, and hemorrhage.

There are no symptoms at all until the disease is advanced.

In advanced stages of heartworm, the symptoms are those of congestive heart failure: dull dry and scruffy coat, lack of energy, coughing, difficulty breathing, fainting – temporary loss of consciousness due to poor blood flow to the brain, exercise intolerance, abnormal lung sounds, abnormal heart sounds, fluid accumulation in the chest and abdomen – caused by the kidneys and liver not eliminating fluid/toxins from the body properly, due to the heavy heartworm infestation, enlarged liver, blood in the sputum, rapid heartbeat, anorexia, weight loss, diarrhea, vomiting, and death.

General Information

  • Heartworm disease is a serious and sometimes fatal disease in dogs. It affects the heart, lungs, liver and kidneys.
  • The disease is becoming more common in this area.

Disease Process

  • The adult heartworms are usually found on the right side of the heart and in the blood vessels supplying the lungs.
  • The larvae of the heartworm circulate in the bloodstream and is the infective stage.
  • The disease is transmitted when a mosquito bites an infected dog and transmits the larvae while biting another dog.
  • Once a dog is infected, it takes approximately six months for the disease to develop.
  • Clinical signs include coughing, difficulty in breathing, weight loss and decrease in activity/exercise.
  • Many dogs are diagnosed with routine testing before any signs of heartworm disease are seen.

Diagnosis and Treatment

  • Diagnosis can usually be made by detecting the larvae in the blood using a simple blood test. In some cases, more sensitive tests are needed to diagnose the disease.
  • Therapy involves approximately a two month period to treat the adult heartworms and larvae. Hospitalization for treatment with an intravenous arsenic compound to kill adult heartworms and follow-up oral medication to kill larvae is necessary and not always 100% effective.


  • It is safer and much less expensive to prevent the disease rather than to treat it.
  • We recommend that all dogs in this area be on heartworm prevention. This involves giving a pill each day of diethylcarbamazine, or a pill once a month of ivermectin. Both medications kill larvae before they develop to adult worms in the heart.
  • Heartworm prevention is given year-round.
  • Prior to starting heartworm prevention, it is necessary to have your animal tested to be sure he/she does not have the disease. This is very important since heartworm prevention given to an animal harboring the disease can cause a fatal shock reaction.
  • Once your animal has been tested, heartworm prevention should be started.
  • After starting the medication, we recommend an annual heartworm blood test.
  • Puppies can be started on heartworm prevention at 2 months of age without a blood test since adult worms in the heart are unlikely at this time. A heartworm blood test is then recommended 6 months after medication has begun and yearly thereafter.