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Heartworm Disease and Your Pet: What You Need to Know

May 29, 2019
Heartworm Disease and Your Pet: What You Need to Know

Spring is here, and hot summer days are not far behind. As temperatures rise, so will the mosquito population, bringing an increase in heartworm disease. More than 1,500 heartworm disease cases were diagnosed in New Jersey in 2018, and 2019 is on course to be as bad. Learn how to protect your furry friend from this life-threatening condition.


What is heartworm disease?

Heartworms, or Dirofilaria immitis, are long, spaghetti-like worms that live in the heart and lungs of infected dogs. The worms’ presence causes several complications:

  • They take up space in the heart and lung vessels, interfering with normal blood flow
  • They cause inflammation of the blood vessels
  • They cause fluid to leak into the lungs, making breathing difficult

If not treated in its early stages, heartworm disease will progress and can be fatal.


How can pets get heartworm disease?

When a mosquito bites a dog infected with heartworms, it picks up microfilariae, or microscopic heartworms, with the blood. Once inside the mosquito, the microfilariae develop into infective larvae that can be passed on to the animal that the mosquito bites next. Over about six months, the worms travel to the heart and lungs and mature into adults that can reproduce. As the worm population exponentially increases, affected dogs experience clinical signs.


Does heartworm disease only affect dogs?

Infected mosquitoes can transmit larval worms to any animal they bite, but dogs are the natural host and the worms die in most other species. Cats can develop the disease, even though they are not a desired host, but while the few larval worms a mosquito transmits may mature to adults, they cannot reproduce in cats. However, even a few adult worms can cause significant inflammation and potentially fatal disease in infected felines.


What are the signs of heartworm disease?

Dogs and cats with heartworm disease display clinical signs caused by inflammation and restricted blood flow. Watch for the following symptoms:

  • Decreased appetite
  • Lethargy
  • Tiring easily
  • Coughing
  • Collapsing suddenly

A heartworm test should be performed during your pet’s annual wellness check to ensure he does not have this deadly infection. The test requires only a few drops of blood, and can often be performed in the office while you wait.


How is heartworm disease treated?

When heartworm disease is diagnosed, further testing, such as blood work, chest X-rays, and an echocardiogram, may be performed to evaluate the severity of infection.

Dogs with active heartworm infection must undergo months of treatment to clear the worms. Multiple medications are used to:

  • Kill adult worms
  • Kill microfilariae
  • Reduce inflammation caused by the worms
  • Eliminate bacteria associated with the worms’ presence


During treatment, dogs are at risk of serious complications. Pieces of dead worms can lodge in small blood vessels and cause pulmonary embolism, so activity must be restricted to leash walks throughout treatment to reduce this risk.

No medication has been approved to kill adult heartworms in cats, so treatment focuses on reducing inflammation and treating symptoms.


How can my pet be protected from heartworm disease?

Since treatment is lengthy, costly, and risky, it is much easier and safer to protect your pet from heartworm infection. Many safe, reliable preventive products are available, from monthly chewable products to biannual injections. Dogs and cats should receive year-round heartworm prevention—mosquitoes are most active when temperatures rise above 50 degrees, but some stay alive in cold weather. Most products will also protect your pet from other parasites that are a year-round threat.

If you have questions about heartworm disease or prevention, our veterinary team can help. Contact us today.