Heartworm Disease In Pets

Dr. Veja Tillman, DVM

Heartworm disease is a preventable, but serious and potentially fatal disease of pets in the United States and many other parts of the world. It is caused by foot-long worms (heartworms) that live in the heart, lungs and associated blood vessels of affected pets. It causes severe lung disease, heart failure and damage to other organs in the body. Heartworm disease primarily affects dogs, cats and ferrets. However, Heartworms can also infect a variety of wild animals such as foxes, wolves, coyotes, lions, panthers, raccoons, opossums, sea lions and seals, as well as others. Because wild species such as foxes and coyotes live in proximity to many urban areas, they are considered important carriers of the disease.

The disease is spread when a mosquito bites an infected pet or animal and then passes the infection on to other healthy pets they bite. Once infected, developing heartworms migrate to the heart and lungs and can grow up to 14 inches long as they mature. If not killed with treatment, they can cause permanent heart and lung damage and even death.

Most pets will not show signs of disease. Common symptoms include coughing, lethargy, decreased appetite, weight loss and difficulty breathing. You may also notice that your pet tires easily or more often after mild to moderate exercise. In cats coughing, difficulty breathing, and vomiting are common. In some cases, pets may suddenly die with no warning signs.    

Diagnosis of Heartworm disease is through a simple antigen blood test performed by your veterinarian. This test detects the presence of adult heartworms. Diagnosis of heartworm disease in cats is more difficult and a series of different tests may be needed to determine if heartworm infection is present.

As with most medical conditions, it is better to prevent heartworms than to treat it. However, if your dog is confirmed to have heartworm disease, there is treatment available. This treatment comes with some substantial risks and your veterinarian will recommend treatment based on the health and wellbeing of your pet. The goal of the treatment (NOT the preventatives) is to kill the adult heartworms in your dog as safely and quickly as possible. Preventatives kill the microfilaria (baby worms) thereby preventing the spread of this disease.

Unfortunately, there is currently no effective and safe medical treatment for heartworm disease in cats.

Heartworm infection is almost 100% preventable. There are several FDA-approved heartworm preventives available in a variety of formulations for your dog (oral tablets, topical applications, and an injectable option) or cat (Orals and topicals only). Your veterinarian can recommend the best method of prevention based upon your pet’s risk factors and lifestyle.

April is Heartworm Awareness Month. Talk to your veterinarian about your pets’ risk of contracting this disease and what preventative would be best for your pet.


Dr. Tillman is a 2002 graduate of Tuskegee University School of Veterinary Medicine. Her veterinary practice and work experience focuses on health and wellness of pets. She is the owner of Just 4 Pets Wellness Center and can be reached at 239-270-5721.

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