First detection of Dirofilaria immitis in a wild red fox from eastern Austria

Abstract Dirofilaria immitis is a parasitic nematode that causes cardiopulmonary dirofilariosis in dogs and other carnivores. This potentially fatal vector-borne disease primarily affects canines and felines. In Austria, reported D. immitis infections have increased in recent years, largely due to imported cases in dogs with travel history to neighboring countries. Dirofilaria immitis is endemic in Hungary, where infections have been reported in dogs and wild foxes. Recently, the first autochthonous D. immitis infection of a pet cat from Burgenland with no travel history was reported in Austria. In 2025, a wild red fox hunted near Parndorf, Burgenland, was dissected and a single nematode was extracted from the fox´s heart. The parasite was examined morphologically, and mitochondrial genome sequencing was performed. Morphological examination identified the parasite as a 14-centimeter-long male specimen of D. immitis . Mitochondrial genome analysis confirmed the morphological results. This is the first time that D. immitis has been detected in a wild animal in Austria. This infection may be of autochthonous origin, given that Parndorf is located 16 km from the Hungarian border and the homing ranges of red foxes do not extend this far. Dirofilariosis is an emerging disease in Austria and alien mosquito species as well as rising temperatures may contribute to the spread of these parasites.