heartworm preventionAs the weather begins to warm up, our thoughts turn to outdoor picnics, yard work, and trips to the dog park. But outdoor weather also brings disease-carrying mosquitoes. One disease of particular concern to pet owners is heartworm disease.

A type of roundworm, the heartworm will infect any size, breed, and shape of dog or cat. Left untreated, heartworm disease is fatal. Even with treatment, it can wreak havoc on your pet’s heart and lungs by the time it’s diagnosed. Let Blue Valley Animal Hospital tell you why heartworm prevention is your pet’s best friend.

How do Pets Get Heartworm?

The heartworm life cycle is long and complex. It begins when a mosquito bites an infected animal (cat, dog, or wild animal) and takes a blood meal, ingesting heartworm microfilaria. The microfilaria develop in the mosquito’s body for 10-30 days. When the mosquito bites a pet, it then transmits the microfilaria to the pet’s bloodstream. There, they circulate and develop for a period of several weeks before finally making their way to the heart and arteries of the lungs. At this point, they mature into foot-long adult heartworms, capable of reproduction. Approximately 6-8 months after infection, they release new microfilaria into the pet’s bloodstream, and the cycle begins again.


Signs of heartworm are elusive and can differ between dogs and cats. In the early stages, there may be no symptoms. As the infection progresses, you may notice:

  • Soft, dry cough with sudden onset
  • Lethargy
  • Difficulty breathing
  • Wheezing
  • Collapse
  • Exercise intolerance


Diagnosis depends on having an accurate history of your pet’s lifestyle and whereabouts, as well as a physical exam and review of symptoms. We may run diagnostic tests, including:

  • Blood tests to detect the antigens released by the adult female heartworm
  • Microscopic exam of the blood to detect microfilaria
  • Cardiac ultrasound
  • X-rays of the heart and lungs

Cats may be harder to diagnose, as they’re resistant hosts; fewer than 6 adult heartworms are typically present. Dogs may have upwards of 30 adult worms living at a time.


While treatment is available for dogs, there is no drug currently approved for treatment in cats. Treatment involves injections of a drug designed to kill the adult heartworms. Success depends on the level of infestation, as well as the health of your dog. Dead/dying heartworms can get caught in the pulmonary arteries, reducing oxygen flow. This is a serious complication; your pet may be monitored in the hospital during treatment. Exercise will be limited in order to minimize this risk. Cats are typically treated for their symptoms, but sudden death and respiratory complications can occur.

Heartworm Prevention

It’s no secret that heartworm prevention is the very best way to protect your pet from this dreaded disease. Luckily, heartworm preventives are safe, easy, and effective. They’re also relatively inexpensive compared to treatment.

It’s important to test your pet once a year for heartworm disease, as well as administer a year-long preventive. Because the life cycle of heartworms is so long, testing ensures we catch any possible breakthrough. Preventives also need to be given on a schedule to break the life cycle before adult heartworms can emerge.

Please contact us with any questions or to schedule an appointment. We’re always here to help!