Without treatment, heartworm disease will shorten a dog’s natural life expectancy. With treatment, especially if the disease is discovered early (hence the veterinary recommendation for annual heartworm testing!), many dogs will have close to a normal life expectancy. Even with treatment, once a dog is infected with heartworm, irreversible damage has been done, especially to the lung tissue. The treatment for heartworms is not without risk, and it can be inconvenient and expensive. Prevention is far wiser than risking disease.
Signs of Heartworm in Dogs
Clinical signs of heartworm disease can be easy to miss and vary depending on the severity of the disease but include:
- Mild cases: May not have any clinical signs, or just a cough.
- Moderate cases: May include a cough, exercise intolerance, and abnormal lung sounds.
- Severe cases: May show abnormal heart sounds, difficulty breathing, liver enlargement, syncope (fainting), fluid accumulation in the abdomen, and death
The onset from the heartworm infection to these clinical signs varies depending on the number of worms in, the body size of the dog, and the dog’s activity level. In general, small, active dogs with higher worm burden have it worse.
How Heartworms Hurt a Dog
The harm that heartworms cause in an affected dog’s body includes:
- Damage to the lungs and the blood vessels in the lungs
- Dead and dying worms can cause thromboembolic events (clots)
- Pulmonary hypertension
- Kidney damage due to accumulation of antigen-antibody complexes
- Large number of heartworms invading the right side of the heart (severe cases)
Heartworms take up much physical space in the heart and interfere with the proper functioning of the tricuspid valve, thus reducing the ability of the heart to pump blood to other parts of the body. This is called “caval syndrome,” and it is characterized by hemolytic anemia, lethargy, weakness, and other signs of right-sided heart failure. Caval syndrome requires urgent surgical extraction of the worms from the heart to save the patient.
Did You Know?
Heartworm is a parasitic disease of dogs and wild canids, including fox and coyote. It also can affect cats, ferrets, sea lions, and rarely, humans. The immature heartworm nematodes (microfilariae) are passed from an infected dog to another susceptible dog via an infected mosquito. After six to nine months of maturation, adult heartworms are 12 inches long and can start breeding to continue the life cycle. Adult heartworms can live for five to seven years.
Prevent Heartworm
Effective preventatives can prevent this awful disease from affecting the health of your beloved dog. These preventatives are economical and convenient, available in oral, topical, and injectable forms. Some preventatives are combined with flea, tick, and intestinal parasite prevention as well.
Using heartworm prevention as directed by your dog’s veterinarian will help maximize your dog’s life expectancy. More information about heartworm disease, its treatment and prevention can be found at the website of the American Heartworm Society.
