Human Heartworm Disease

Human heartworm disease is a very rare illness. Unlike similar disease in canines and cats, however, the heartworm that can affect humans does not take up residence in the heart, but instead roots itself and grows in other organs, usually the lungs.

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Heartworms are transmitted by mosquito bites, fleas, ticks and flies. The heartworm larvae is deposited into the host--usually a dog or cat--through the saliva of an infected insect. The microfilaria, or young heartworms, grow inside the infected host, taking residence in various parts of the body until they mature and eventually move into the upper right chamber of the heart, veins and other nearby organs. Though the heartworm may thrive in many different organs inside the host, the heart receives the most damage from invading heartworms, as the host's immune system attempts to fight off the foreign body, creating a number of autoimmune symptoms.


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Although symptoms of heartworm disease in dogs and cats can range from blindness, lameness, coughing, muscle aches, fatigue, cramping, diarrhea, weight loss, hair loss and eventual death, heartworm in humans does not present classical "disease" symptoms. Instead, the organ affected by heartworm may form nodules as the worms die off, causing an immune reaction known as human pulmonary dirofilariasis. There may be no symptoms associated with human heartworms. Often, an affected person will only find out about the illness as the result of an X-ray or CT scan. Some patients, however, can experience coughing, fever, fatigue or chest pains.


Human heartworm infestation can be detected visually through an X-ray of the infected area, but the diagnosis will not be definitive without further testing to rule out cancer and other conditions that cause lesions. If you have the characteristic nodules on your X-ray, your doctor will probably want to perform a biopsy to get a conclusive diagnosis.

Contributing Factors

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Humans who live in areas where there is a large population of dogs--particularly dogs that do not receive regular preventative veterinary care--are more likely to get heartworms than those that do not live in these areas. Men over 50 years old are twice as likely to be diagnosed with heartworms than younger men or women of any age. This could be due to the fact that older men are more likely to get chest X-rays than younger men or women. People who live in mosquito-infested areas are more likely to get heartworms than those who do not.


To date, there have been no reported cases of human deaths due to heartworm disease. Because the human body does not make a good host for heartworms, once the worms die, treatment can be limited to symptomatic relief of conditions secondary to the infestation, and full recovery is possible.