Lissonema sicki, an emerging air sac nematode of European owls: introduction, host switching and rapid establishment on a Mediterranean island.

In recent years, air sac parasitic helminths have been reported to cause severe disease in birds. In addition, various species appear to be expanding and infecting new avian hosts in various regions worldwide. In this context, an air sac nematode was initially detected in 2014 infecting the Eurasian scops owl, hospitalized in the local wildlife hospital in Mallorca (Balearic Islands, Spain). Years later, the parasite was detected in 2 other owl species. Air sac nematodes had never been reported in the Mallorcan Strigiformes before. A comprehensive molecular and morphological characterization analysis, including scanning electron microscopy, was required for species confirmation. The species was identified as Lissonema sicki, a parasite infrequently reported in South American owls. Since its first introduction to Mallorca, it has dramatically increased in prevalence in hospitalized birds, being highly prevalent in the Eurasian scops owl (41%), in the long-eared owl (11%) and in the barn owl (4%). The introduction pathway of this parasite to Europe remains unknown. This discovery underscores the expanding range and impact of L. sicki, emphasizing the importance of ongoing surveillance and research to comprehend and manage the implications of its emergence in new territories.