Sounds really scary. That’s because it is. Heartworm disease is a serious and potentially fatal disease in 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, causing severe lung disease, heart failure and damage to other organs in the body. Heartworm disease affects dogs, cats and ferrets, but heartworms also live in other mammal species, including wolves, coyotes, foxes, sea lions and—in rare instances—humans. Because wild species such as foxes and coyotes live in proximity to many urban areas, they are considered important carriers of the disease”, warns American Heartworm Society.

Pet MD states that “dogs suffering from heartworm disease are parasitized by the organism Dirofilaria immitis, a nematode (roundworm) commonly referred to as the heartworm. The severity of heartworm disease in dogs is directly dependent upon the number of worms present in the body, how long they’ve been there, and the response of the host (dog)”.


It can cause lasting damage to the heart, lungs and arteries, and can affect the dog’s health and quality of life long after the parasites are gone. Prevention is by far the best option.


Typical signs of heartworm disease include exercise intolerance, coughing, and poor body condition.


There are four classes of Heartworm Disease.

  • Class I – Asymptomatic, meaning they exhibit no visible symptoms, or minimal signs such as an occasional cough.
  • Class II - coughing and intolerance to a moderate level of exercise. Class III - generalized loss of body condition, more extreme exercise intolerance, labored breathing, and a pot-bellied appearance associated with fluid accumulation in the abdomen as a result of right-sided heart failure.
  • Class IV - Caval syndrome caused by the presence of so many worms that they block the flow of blood into the heart.


Bites of mosquitos that carry the infective heartworm larvae spread heartworms to dogs. The larvae migrate through the dog’s body until they reach the heart and blood vessels within the lungs. The process that takes about six months.

Factors of risk for heartworm disease include exposure to mosquitos, residence in endemic regions, and lack of proper preventative medications.


All it takes is a quick blood test to screen a dog for heartworms. 


“Heartworm disease is preventable with the administration of a heartworm prophylaxis (preventative medication), as recommended by a veterinarian. For dogs who do contract heartworm disease, the prognosis is good for mild to moderate cases with appropriate and timely treatment. Dogs with more severe cases may suffer from serious short- and long-term complications associated with the disease and its treatment. Treating heartworms is expensive and always carries some risk to the dog. It is certainly better to prevent the disease than to deal with its consequences. Without treatment, most cases of heartworm disease are eventually fatal” says Pet MD.

The American Heartworm Society recommends that you “think 12:”

(1) Get your pet tested every 12 months for heartworm and

(2) Give your pet heartworm preventive 12 months a year.

Can Cats Get It?

Yes, they can. “Heartworms represent an increasingly recognized problem in cats. As in dogs, heartworms are transmitted by feeding mosquitoes and, once mature, end up in the right side of the heart and the large vessels of the lungs. For cats, the likelihood of heartworm infection is directly related to the number of infected dogs in the area. While infection rates in cats (not the typical host for heartworms) are lower than in dogs, studies have shown that up 10-14% of shelter cats are infected. Because mosquitoes can transmit the disease, being an indoor-only cat does not prevent a cat from getting infected. Signs of heartworm infection in cats can vary in severity from asymptomatic to sudden death”, explains Pets and Parasites.

To make sure you beloved pet is safe from Heartworm, make sure you have a great Veterinarian to examine your animal and help you keep them safe.

Animal Care Center in Smyrna, GA, is owned and operated by Otto H. Williams, DVM. The veterinary practice specializes in complete healthcare for cats and dogs and offers services including preventative, surgical and nonsurgical care, internal medicine, grooming and boarding to Cobb County and surrounding cities such as Vinings, Marietta, Mableton and Sandy Springs. Call today at 770.438.2694 or request an appointment.

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