Heartworm disease is a deadly condition that affects pets throughout the United States. Although the risk is greater in the hot, humid southern states, pets in New York are still in danger. According to the American Heartworm Society, local veterinary hospitals diagnose up to 25 cases of heartworm disease per year. Fortunately, the disease is preventable, and keeping your pet safe is easy.

What are heartworms?

Heartworms—Dirofilaria immitis—are parasitic worms that complete their life cycle inside a canine host’s body. In the larval form, they are too small to be seen with the naked eye. A fully mature worm, however, can measure up to 12 inches long.

How do pets contract heartworms?

Mosquitoes transmit heartworms to pets. Mosquitoes feed on blood, and when they bite an animal infected with heartworms, they pick up microscopic larvae along with the blood. The larvae then develop inside the mosquito and can be transmitted when the mosquito bites another animal and injects infective larvae.

What is heartworm disease?

Heartworm disease develops once larvae are introduced into your pet’s body. Over the next 4 to 5 months, the larvae migrate to the blood vessels of the lungs, where they develop into adult worms. Adult worms multiply and produce microscopic worms, called microfilariae, which circulate through the bloodstream until they also settle in the lung vessels. The worm population can grow so large that adult heartworms take over the right side of the heart.

The presence of worms within the heart and large lung vessels causes inflammation and slows blood flow. Affected dogs may develop congestive heart failure, and without treatment, will eventually die.

Are dogs the only animals at risk for heartworm disease?

Dogs are the heartworm’s intended host, but other species can also be affected. An infected mosquito can deposit microscopic larvae into any animal, but the larvae simply die inside most species. The dog is the only species in which the worms can reproduce to cause fulminant disease.

In cats, the few larvae deposited during a mosquito bite often don’t die and may develop to maturity, but they cannot reproduce. Heartworms are still a concern for cats because even a few worms can cause significant inflammation and damage to their lungs.

What are the signs of heartworm disease?

The presence of heartworms in dogs causes inflammation and obstruction to normal blood flow through the heart and lungs. Clinical signs can be vague:

  • Lethargy
  • Weakness
  • Tiring easily
  • Coughing
  • Vomiting

The few worms in an infected cat may cause wheezing and coughing, but often no symptoms. Cats can die from a heartworm infection without ever showing clinical signs.

How is heartworm disease diagnosed?

Heartworm disease can be diagnosed with a simple test that requires just a few drops of your pet’s blood. A heartworm test should be performed at every canine and feline annual wellness examination. If an animal tests positive, further testing is performed to evaluate the extent of infection and damage caused by the worms.

Can heartworm disease be treated?

Treatment is available for heartworm disease in dogs, but it’s lengthy and costly, and carries significant risk. The medication used to kill adult worms is administered by intramuscular injections over several months. Additional medications are also used to kill microfilariae and decrease inflammation.

During treatment, dogs must be kept calm—with short leash walks for potty breaks only—to prevent potentially deadly complications. The worms disintegrate and break apart as they die, and the dog’s body may resorb them. Pieces of dead worms can lodge in the blood vessels of the lungs and cause a deadly pulmonary embolism. This complication is more likely with activity that increases heart rate and blood flow.

No medication is available that can safely kill adult heartworms in cats. Treatment is instead aimed at decreasing the inflammation caused by the worms’ presence until they die on their own.

How can I protect my pet against heartworm disease?

Because of the deadly consequences of heartworm disease and potential complications of treatment, preventing heartworm disease is important. Many safe preventive products are available—our veterinarians can prescribe one that will best fit your pet’s needs. Most heartworm products are given monthly, and year-round prevention is critical. Although most mosquitoes die off during the winter, some survive and will emerge after just a few warm days above 50°F. Most heartworm products will also prevent other parasites that are a year-round threat.

If your pet is not currently on a heartworm preventive, schedule an appointment today. We will perform a quick test to confirm your furry friend is heartworm-free and then prescribe a product that will ensure your pet never suffers from this devastating disease.

Questions about heartworm disease or prevention? Give us a call.