How long does a heartworm live?

The adult form of the heartworm (Dirofilaria immitis) can live for approximately 5-7 years within the heart and pulmonary arteries of an infected host, usually a dog. The lifespan of a heartworm is closely tied to its life cycle stages. While inside the host, adult heartworms reproduce, releasing microfilariae, which circulate in the bloodstream. These microfilariae can live for approximately 6-12 months. The life cycle of heartworms requires a mosquito vector for transmission between hosts.