Protecting Your Pet From Heartworm Disease

BY Elizabeth Kowalski, CVT, FFCP

Dog sitting in the woods

The American Heartworm Society estimates that more than a million U.S. pets currently have heartworm disease This devastating disease causes severe heart and lung damage and, left untreated, can eventually become fatal. Fortunately, heartworm disease is completely preventable. Learn the true effects of heartworm disease and the steps you can take to reduce your pet’s risk.

What is heartworm disease?

Heartworm disease is caused by parasitic worms that live in an infected pet’s heart, lungs, and blood vessels. Although heartworms prefer dogs, cats can also become infected and suffer severe disease. Heartworms can easily multiply to produce 30 to 100 worms in a single dog, but cats typically harbor only a few mature worms. Infected dogs are often asymptomatic for months or years before showing disease signs, while cats have an unpredictable response. In any infected pet, heartworms can cause deadly heart failure.

Heartworms are transmitted by infected mosquitoes that carry microscopic heartworm larvae called microfilariae. Microfilariae are passed to pets via a mosquito bite, migrate through the pet’s body, and eventually mature into 12-inch-long adult worms. This process takes several months, and the immature worms cause inflammation and damage along the way. Mature heartworms cause continued damage, and eventually accumulate to numbers large enough to cause life-threatening heart failure. The larvae circulate in the blood of infected pets and wild animals, which become disease reservoirs that infect more mosquitoes.

Understanding heartworm risks

Heartworm disease can affect pets of any age, breed, lifestyle, or location. The likelihood of a pet contracting the disease increases in warm, humid regions with thriving mosquito populations and in areas where other animals are already infected. However, pets in all climates are at risk. In fact, there are pets with heartworm disease in all 50 states. Even indoor pets can contract heartworms when infected mosquitoes venture indoors.

Dogs are more likely than cats to host heartworms and develop heartworm disease. Unfortunately, the number of infected cats is unknown, because testing cats is more complicated than testing dogs, which involves only a simple blood test. AAHA guidelines recommend that dogs be tested annually. Cats are typically tested only if heartworm disease is suspected.

Heartworm treatment and prevention

Heartworm treatment is an involved and expensive process. In dogs, adult worms can be killed only by a specific drug treatment protocol involving painful injections and several months of strict cage rest. Unfortunately, no safe treatments exist for cats, so infected cats must be monitored closely and treated symptomatically.

Heartworm prevention is much easier than treatment. Although some pet owners assume that routine deworming can prevent or eliminate heartworm infections, these medications are ineffective against heartworms. Heartworm disease is preventable only with specifically designed medications that are safe and effective. Routine prevention is much less expensive than heartworm treatment, and preventive medications are available in many forms, including monthly oral and topical formulations, as well as annual injections. Your AAHA-accredited veterinarian can help you decide which product is best for your pet.

Managing heartworm risks

In addition to providing regular heartworm prevention, you can reduce your pet’s risk of heartworm infection with these steps:

  • Follow veterinary recommendations — Schedule regular veterinary check-ups to discuss your pet's heartworm disease risk and determine prevention measures that cover heartworms and other common parasites.
  • Avoid mosquitoes — Minimize your pet's exposure by keeping them indoors during peak mosquito activity.
  • Heartworm testing — Ensure your pet receives annual heartworm testing, whether or not they are taking a preventive. Early detection is key to effective treatment and heartworm disease management.
Heartworm Awareness Month

Each April, Heartworm Awareness Month raises awareness about heartworm disease prevalence and highlights prevention measures all pet owners can take to reduce disease spread. Heartworm Awareness Month reminds pet owners to prioritize their pet's health by taking proactive measures against this common illness.

Heartworm disease poses a significant threat, but pet parents who understand the risks of heartworm infection and take proactive steps can keep their pets safe. Speak to an AAHA-accredited veterinary team member to learn more about protecting your pet from heartworm disease.