Dog heartworms cannot complete their life cycle in people and do not survive for very long in them, so people rarely have symptoms.
Most infected people do not have symptoms, but if the worm travels to the lungs and dies there, people may cough and have chest pain.
Doctors may discover dog heartworm infection when they see a lump in the lungs on a routine chest x-ray.
No treatment is needed because the infection resolves on its own.
(See also Overview of Parasitic Infections Overview of Parasitic Infections A parasite is an organism that lives on or inside another organism (the host) and benefits (for example, by getting nutrients) from the host at the host's expense. Although this definition actually... read more and Filarial Worm Infections Overview Filarial Worm Infections Overview Filarial worm infections are caused by certain roundworms and affect different parts of the body depending on the species of worm. There are many species of filarial worms, but only a few infect... read more .)
Dog heartworm infection is a filarial worm infection that rarely affects people because the worms cannot complete their life cycle in people and do not survive for very long in people.
Dog heartworm infection can be transmitted when an infected mosquito bites a person and deposits larvae of the worm in the bite. The larvae usually die in the skin. However, sometimes the larvae live long enough to travel through the blood to the lungs and die there, forming a lump (nodule), which may be seen on a chest x-ray. Rarely, larvae travel to the eyes, brain, or testes and form lumps there.
Doctors may discover dog heartworm infection when they see a lump in the lungs on a routine chest x-ray. The lump can resemble a lung tumor. Doctors may do specialized radiological tests or take a sample of the lump (biopsy) and examine it under a microscope to be sure that it is not a cancer.