Onchocerca flexuosa. sp. (Nematoda: Filarioidea) in Japanese Wild Sika Deer (Cervus nippon): Pathological and molecular identification.

Subcutaneous nodular onchocercosis was detected and investigated in 17 Japanese Sika deer (Cervus nippon), captured in Gifu and Shiga Prefectures/Japan, in the period between 2016 and 2017. The worms were found in all the seventeen deer within characteristics subcutaneous nodules dispersed mainly in the back (especially in the lumbar region and flanks), with few scattered nodules were located at the forelimbs and neck. The all collected nodules were examined stereo-microscopically. The parasites were extracted from the nodules and identified through morphological and histopathological examinations. Molecular identification through sequencing of the following genes; internal transcribed spacer subunit 2 (ITS2)-28S ribosomal RNA (28S rRNA), cytochrome c oxidase subunit 1 (cox1) and mitochondrially encoded NADH dehydrogenase subunit 2 (NAD2) were performed. The histopathological, molecular and phylogenetic analysis demonstrated that, the filarial nematode isolated from Gifu and Shiga Prefectures in Japan is O. flexuosa. This is the first report about presence of O. flexuosa in Japanese Sika deer (Cervus nippon) in Gifu and Shiga Prefectures. Supplementary Information: The online version supplementary material available at 10.1007/s12639-021-01453-3. © Indian Society for Parasitology 2021.