Dirofilaria is a genus of roundworm (nematodes). These worms cause Dirofilariasis in humans defined as infection by filarial nematodes of the genus Dirofilaria.Two subgenera, Dirofilaria (Dirofilaria) species and Dirofilaria (Nochtiella) species are recognized. Dirofilaria (Dirofilaria) immitis is the most frequent agent of pulmonary dirofilariasis. Although D.