Heartworm is a parasitic worm called Dirofilaria immitis that infects mainly dogs through a mosquito bite. An infected mosquito injects a larval stage worm under the dog’s skin and travels through the body to the heart and blood vessels of the lungs where it matures over 6 months, and breeds releasing microfilariae that are ingested by mosquitos when they bite an infected dog. It usually takes several years before dogs show clinical signs of infection and at that point, the dog has advanced heartworm disease and substantial damage to the heart, lungs, blood vessels, kidneys, and liver, however, there are treatments available. The most common diagnostic assay used for heartworm is the ELISA antigen test which uses serum, plasma, or whole blood specimens for testing.