Dirofilariasis (Dog Heartworm Infection) By Chelsea Marie, PhD, University of Virginia; William A Petri, Jr, MD, PhD, University of Virginia School of Medicine Reviewed / Revised Sep 2022 View Patient Education Dirofilariasis is a filarial nematode infection with Dirofilaria immitis, the dog heartworm, or other Dirofilaria species, which are transmitted to humans by infected mosquitoes.