Zoonotic infection caused by Onchocerca japonica (Nematoda: Filarioidea) in a 69-year-old woman in Kanto Region, Eastern Honshu, Japan

• Published in: Parasitology international 2022-12, Vol.91, p.102643, Article 102643
• Main Authors: Okazaki, Daijiro, Fukuda, Masako, Hebisawa, Akira, Uni, Shigehiko, Junker, Kerstin, Suzuki, Yoshio, Nakano, Michiyo, Agatsuma, Takeshi, Hasegawa, Hideo, Yamada, Minoru, Nakatani, Jun, Hara, Tatsuru, Martin, Coralie, Kimura, Daisuke, Takaoka, Hiroyuki
• Format: Article
• Language: English
• Subjects: Emerging infectious disease; Filariae; Japanese wild boar; Life Sciences; Mitochondrial cox1 sequencing; Onchocercosis; Transverse ridges
• ISSN: 1383-5769; 1873-0329
• DOI: 10.1016/j.parint.2022.102643

Reports of zoonotic infections caused by the filarial nematode Onchocerca japonica have recently increased in Japan. A 69-year-old woman living in Sosa City, Chiba Prefecture, Kanto Region, Honshu, developed a painful nodule at the metacarpophalangeal joint of the index finger of her right hand. The causative agent was identified as a female O. japonica based on the histopathological characteristics (i.e., cuticle with transverse triangular ridges but without inner striae) of the biopsy specimens of the nodule. The species identification was corroborated by cox1 gene sequencing of the worm tissues isolated from paraffin-embedded sections of the specimens. Subsequent to the excision of the nodule, followed by anthelmintic treatment, the patient remained asymptomatic. Human infection with O. japonica has not previously been reported in Kanto Region, Eastern Honshu. The present case is likely linked to the recent expansion of the geographic range of the Japanese wild boar into this area. [Display omitted] •First case of zoonotic onchocercosis diagnosed in woman in Kanto Region, Japan.•Nodule in right hand contained young adult female of Onchocerca japonica.•Filarial section shows cuticle with triangular ridges but without inner striae.•Cox1 sequences of filaria corroborate morphological identification.•The Japanese wild boar (natural host) is undergoing range expansion in Japan.