ABSTRACT
Dirofilariasis is a multisystemic disorder with the lungs, heart, liver, and kidneys being the main organs affected. While the pathogenesis, pathology, and consequences of the disease have been the subject of many reviews most of the reports on the pathology of dirofilariasis refer to advanced natural disease. The predominant lesions in dirofilariasis are centered on the pulmonary artery and its branches. The pulmonary parenchyma becomes secondarily involved as an inflammatory reaction spreads from the site of parasitic thrombosis which occurs following death of the adult worms. The experimental work on immune-mediated occult dirofilariasis does show that an interstitial pneumonitis can occur as a result of microfilarial retention and that this may become diffuse and extensive with the damage to the pulmonary microvasculature leading to hemosiderosis. Renal disease plays an important role in canine dirofilariasis. The nature of the changes and, more importantly, the pathogenesis of the changes that occur are complex and require further elaboration.
