Heartworm is a parasitic roundworm (Dirofilaria immitis) that infects dogs and other animals.
Many dogs, particularly sedentary ones, will exhibit no signs of infection. Others will develop a cough, particularly upon exertion, and may tire easily. Animals with severe infestations may cough up blood, lose significant amounts of weight, pass out, and eventually develop congestive heart failure.
In some cases a blood test can detect the presence of heartworm if the infection has reached the stage where symptoms are present (usually 6-8 months after the initiating mosquito bite). In some cases, x-rays may be ordered to determine the extent of the damage caused by the infection.
Medications are available to treat the infection, however these can be harsh. During treatment and for an extended time thereafter, the animal will be required to rest in order to allow the dead worms to be absorbed into the system. Dead worms that break off prematurely can be carried to the lungs where they can cause damage. On rare occasions, surgery is sugg

ested.
Due to the potential severity of both the disease and its treatment, prevention is a step all dog owners across the contiguous U.S. should practice. Concerned owners should consult with their veterinarian on preventive medication. Since mosquitoes are the transmitters of heartworm, mosquito control is another important step pet owners can take in preventing infection.