Heartworm Risks and Prevention Tips

By: Chewy EditorialUpdated:

Heartworm Risks and Prevention Tips
Photo: Chewy Studios

Heartworm Risks and Prevention Tips

Heartworm disease is a serious and potentially fatal disease that is transmitted by mosquitoes. As a small animal veterinarian practicing in South Florida, I sadly diagnose heartworm disease all year long, and am all too familiar with the severity and consequences of heartworm disease. Many parts of the country that experience colder weather during fall and winter seasons have a significant decline in the mosquito population, so there is less risk of infection to dogs and cats in those areas. Regardless of where you live, monthly pet prescription heartworm medicine is safe, easy and crucial in preventing this disease. Let’s explore some of the key aspects of heartworm disease, and most importantly, how we can keep our pets living long, healthy lives, free of heartworm disease.

What Is Heartworm Disease?

Heartworm disease is a parasitic disease that is transmitted to dogs and cats by infected mosquitoes. Once infected, the parasites grow and develop into foot-long worms that live in the heart, lungs and vessels. Heartworms in dogs and cats can cause severe lung disease, heart failure and damage to other organs in the body.

Which Animals Can Be Infected With Heartworms?

Heartworm disease affects dogs, cats, wolves, coyotes, foxes, sea lions, ferrets and, in rare instances, even humans. Dogs are a natural host for heartworms, which means once the dog becomes infected, the heartworms can mature and produce offspring—sometimes up to several hundred worms—while living in the host. Cats can become infected with heartworm disease as well, but they are atypical hosts for this parasite. Most heartworms in cats do not survive to the adult stages, so a cat may be infected with one to three worms, while a dog can be infected with several hundred. Still, cats can endure severe damage from immature worms and can develop heartworm-associated respiratory disease (HARD), just like dogs can. Unfortunately, the medication used to treat heartworms cannot be used in cats, so prevention is the only way to protect your cat from heartworm disease.

How Does My Pet Become Infected With Heartworm Disease?

Mosquitoes play an essential role in maintaining and spreading heartworm disease. Mosquitos transmit the disease by feeding on infected animals, and picking up “baby worms,” which then develop into larvae in the mosquito in 10 to 14 days.  When an infected mosquito bites and takes a blood meal from an animal, it deposits infected heartworm larvae into the animal, and the animal becomes infected with heartworm disease.

What Are The Clinical Signs of Heartworm Disease?


Early stages of heartworm disease:

  • No heartworm symptoms at all—please take note!
  • Mild, persistent cough
  • Reluctance to exercise
  • Fatigue, especially after exercise
  • Decreased appetite
  • Weight loss

Later, more advanced stages of heartworm disease:

  • Heart failure
  • Swollen belly
  • Caval syndrome (sudden blockage of blood flow to the heart), which causes labored breathing, pale gums, and dark, bloody coffee-colored urine


  • No heartworm symptoms at all!
  • Coughing
  • Asthma-like attacks
  • Periodic vomiting
  • Lack of appetite
  • Weight loss
  • Difficulty walking
  • Fainting
  • Seizures
  • Sudden collapse

How Do I Test for Heartworms in Dogs and Cats?

Mosquitoes are present all year in South Florida. The risk of pets becoming infected in warmer climates where mosquitos thrive is far greater than in places with cooler fall and winter seasons. I require that all my patients be tested for heartworm disease once per year to ensure that all preventative medications are working effectively. Even when my patients are on consistent monthly heartworm prevention, it is imperative to test yearly. Heartworm preventatives are highly effective, but there are pets that can become infected, even while taking them. No matter where you live, yearly testing is the general guideline for all veterinarians and is recommended by the American Association of Heartworm Disease.  The test requires a small drop of blood and is processed in 10 minutes at your vet’s office. Some veterinarians may send the test out to a diagnostic laboratory.

Is There a Treatment for Heartworm Disease?

For most dogs, if they become infected with heartworm disease, there is a treatment. If the disease is not too far advanced and your pet can endure it, your pet can be treated. This normally involves a strenuous and complex three-month regimen with restricted exercise, heartworm prevention, antibiotics, steroids (if needed), and injections of Immiticide to kill the adult worms. The treatment is costly and stressful for dogs—oftentimes, they become ill from the side effects.

Unfortunately, there is no approved treatment for heartworms in cats, and the drug that is used to treat dogs is not safe for cats. If your cat is diagnosed with heartworm disease, our goal as veterinarians is to stabilize and manage the disease. On occasion, cats can spontaneously clear the heartworms from their systems; however, the damage left by the heartworms can be permanent. Many times, depending upon the severity of the clinical signs, the disease and the symptoms can be treated to maintain long-term health.

How Can I Protect My Pet Against Heartworm Disease?

I cannot stress enough the importance of monthly heartworm prevention for both cats and dogs. Heartworm preventatives are inexpensive, easy to administer and very safe. Heartworm disease is an extremely serious, progressive, and sometimes fatal disease. As mentioned before, there is no approved treatment for heartworm disease in cats. And the options for dogs are costly and, more importantly, strenuous on a dog’s body. Heartworm disease can result in permanent damage to the heart, lungs and arteries, and it can affect your pet’s health and quality of life long after the parasites are gone. For this reason alone, prevention is by far the best way to keep your pets safe, healthy and happy.

I hope this article was helpful in learning about heartworm disease and how to keep your pet safe. The earlier the disease is detected, the better the chances are that your pet can be treated and not suffer from long-term effects. Yearly testing and monthly preventatives are crucial for preventing heartworm symptoms. As always, my goal is to keep our pets living long, happy and healthy, disease-free lives. Providing preventative care to my patients is much better than treating disease.

By: Dr. Alison Birken
BeChewy Collaborator & Owner of Victoria Park Animal Hospital.




By: Chewy EditorialUpdated:

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