New MosquitoCases of heartworm disease among dogs and cats have been on the rise over the past five years. Yet, many pet owners falsely believe it’s something that happens to “someone else’s pet” or only in rural areas.

Misconceptions about heartworm disease have led to the proliferation of the disease, expensive veterinary bills, and, sadly, the untimely deaths of tens of thousands of pets a year.



Heartworm: A Growing Concern

Heartworm disease affects every state in the U.S. and is most often found in coastal climates where mosquitoes tend to thrive. Although heartworm is much more common in dogs, we are seeing more cats and ferrets diagnosed, especially among shelter populations.

It is currently estimated that over one million dogs are infected with heartworm, and yet only 30% of these cases will be diagnosed by a veterinarian.  Further to this, roughly only half of dog owners keep their pets on a preventive.

This vulnerability in canines (as well as in unprotected cats) and the increasing presence of urban wildlife, which play host to the parasite as well, illuminate why this disease continues to spread.

How is Heartworm Disease Contracted?

Essentially, heartworm disease develops after an animal is bitten by a mosquito infected with heartworm microfilariae, which is contracted through biting other wild animal. The mosquito hosts the microfilariae until they become heartworm larvae.

The mosquito then transmits the infection by transferring parasitic larvae into the bloodstream of a dog or cat. As the infection develops, the parasites move through the blood vessels to the major vessels of the heart and lungs. This is where the mature worms remain and continue to grow and reproduce.

Generally this process takes about 6-7 months in canines and around 8 months in felines.

Over time, these worms begin to compromise organ health, although sometimes it takes months or years for a pet to show physical symptoms.

What are the Symptoms?

Unfortunately, because heartworm takes some time to develop and there can be few, if any, symptoms, many infected pets are never diagnosed until the disease has reached its most severe stages.

When symptoms do arise, they might include:

  • Persistent cough
  • Tires easily after exercise
  • Vomiting
  • General lethargy
  • Weight loss
  • Asthma like symptoms (especially with cats)

Detection and Treatment

Heartworm testing is available through your veterinarian, and must always be done prior to beginning a heartworm preventative. If your pet has not been on a preventive (even if you missed one month), it is important to screen for the presence of heartworm. This is in part due to the often subtle symptoms of the disease, but also because currently infected pets can have adverse reactions to being placed on a preventive.

Treatment varies in both approach and duration depending on what stage of heartworm disease your pet is in. In many cases, medications targeting the adult worms, as well as the microfilariae in the bloodstream, are used, along with frequent monitoring, X-rays, and bolstering immunity. Sometimes surgery is required.

Treatment for cats is a bit more complex as we do not yet have any FDA-approved medications.

Because heartworm disease is such a deadly infection, as well as difficult and costly to treat, we believe year-round parasite prevention is the best way to keep your pet protected. We encourage you to speak to your veterinarian about available preventives as well as annual screening.