The Heart Of The Matter: Heartworm Disease and your Dog

posted: by: CCVH Tags: "Clinic Specials" "News" 

Heartworm disease is caused by an organism known as (Dirofilaria immitis). Our domestic dogs are the preferred host of heartworms but, more than 30 other species of animals can be infected (including coyotes, cats, ferrets and even sea lions and humans!). Heartworm disease is transmitted when a mosquito carrying the infective heartworm larvae bites a dog and transmits the infection to the dog. The larvae then grow and develop within the dog and migrate throughout the body. They develop into sexually mature male and female worms that can then mate and release their offspring (known as microfilariae) into the blood stream. The mature adults take up residence in the heart, lungs and associated vessels.

Heartworm disease occurs throughout the United States and has been detected in all 50 states. All dogs, regardless of their age, sex, or habitat, are susceptible to heartworm infection. It takes about 6-7 months after the infective larvae enter our dogs from the mosquito to be detected in the blood. The mature adults become fully grown around a year after infection and can live up to five or seven years. The number of worms that affect the dog can be very high, ranging from one to 250!

The onset of evidence of heartworm disease greatly varies depending on the number of adult heartworms present, the time of infection, and the activity level of the dog. The more adult heartworms that a dog carries, the more severe heart and lung disease changes can be. For instance, a very active dog is more likely to develop severe disease with smaller amounts of heartworms as the heart becomes weakened trying to meet the higher work demands.

Heartworm disease can cause a variety of clinical signs in our pets depending on the stage of infection and number of adult worms. The majority of clinical signs are related to heart, lung, liver, and kidney disease. Owners often note a cough, exercise intolerance, a distended abdomen or collapse. Severe heartworm disease can also result in death.

Diagnosis of heartworm disease can be made based on a thorough history, a physical exam, recognition of clinical signs, and several diagnostic tests.  In our clinic, we use a blood test to detect heartworm disease.  We are also able to look for the microfilariae in the blood, though they can be absent even in the presence of disease. Heartworm tests should be performed annually to ensure that all dogs are negative prior to starting or continuing heartworm prevention. This also allows us to ensure the effectiveness of prevention products in dogs that are on these products year round. Other advanced tests, including x-rays and ultrasound, can be performed.

Once diagnosed, heartworm disease can be very costly to treat.  Here at C.C. Veterinary Hospital, we follow protocols recommended by the American Heartworm Society to treat infected dogs.  These protocols involve different steps over several months and are not without risk to the dogs. Heartworm is also becoming increasingly more expensive to treat due to shortages of the medications used in the treatment protocol.

With the rising costs of treating heartworm disease and the prevalence nationwide, it makes it even more important to make sure your dogs are protected with heartworm preventative. Heartworm prevention is a much safer and more economical way to manage heartworm disease. There are a variety of options including monthly chewables, tablets, topicals, and a 6-month injection. When these products are administered on a routine schedule, heartworm infection can be prevented easily. The American Heartworm Society recommends year-round heartworm prevention. With varying weather patterns from year to year, to ensure that adequate protection against heartworms is achieved, it is best to continue prevention year round. Stop in today and talk to us about which heartworm preventative is the best option for you and your dogs!

For more information on heartworm disease, contact us or check out the American Heartworm Society’s website at