RESUMEN
The bear roundworm Baylisascaris transfuga has been identified in several host bears (Ursinae). However, limited genetic information is available on the bear roundworm in Japanese populations. This study evaluated the genetic composition of bear roundworms isolated from wild Japanese black bears indigenous to Lake Towada, Japan. First, we conducted genetic and/or molecular phylogenetic analyses based on cytochrome c oxidase subunit II and internal transcribed spacer 2 among Baylisascaris species. These analyses revealed that the identified roundworms were genetically B. transfuga. In addition, the average body size of the obtained roundworms in this study was almost the same as that previously reported for B. transfuga. This study represents an important step in genetic research on the roundworm B. transfuga in Ursinae bears not only from Japan but also from the rest of the world.