Tapeworm infection incidence in rural Japan points to a common environmental source of infection
Dibothriocephalus nihonkaiensis is a zoonotic tapeworm transmitted to humans through consumption of raw or undercooked fish or wild meat. Between 2022 and 2023, Yamagata Prefecture reported an increase in cases compared with 2017-2021, when none were observed. We conducted a clinical and environmental investigation to clarify infection sources. Four confirmed and one suspected patient were identified, all presenting with gastrointestinal symptoms. Exposures were linked to raw cherry salmon (Oncorhynchus masou) in three cases and undercooked bear meat in one case. Praziquantel treatment (10-20 mg/kg) was effective, with eight worms (76-210 cm) recovered. Environmental surveillance detected D. nihonkaiensis in 33.3% of bear feces (20/60) and 21.8% of wild fish samples (17/78). Phylogenetic analysis showed close genetic relatedness among human, bear, and fish isolates, indicating a shared transmission cycle. These findings confirm zoonotic transmission of D. nihonkaiensis in Yamagata and highlight the need for food safety awareness and environmental monitoring.
Authors
- Yusuke Okuma (ORCID: https://orcid.org/0000-0001-5743-0149)
- T Aoyagi
- Phatthranit Phattharapornjaroen (ORCID: https://orcid.org/0000-0002-4391-2929)
- Sam Trowsdale (ORCID: https://orcid.org/0000-0001-8907-6885)
- Mohan Amarasiri (ORCID: https://orcid.org/0000-0002-3509-3433)
- Longzhu Cui (ORCID: https://orcid.org/0000-0002-8909-3885)
- Kazunari Sei (ORCID: https://orcid.org/0000-0002-0684-6002)
- Talerngsak Kanjanabuch (ORCID: https://orcid.org/0000-0002-2996-8934)
- Anthony Kicic (ORCID: https://orcid.org/0000-0002-0008-9733)
- Parichart Hongsing (ORCID: https://orcid.org/0000-0002-2031-3472)
- Dhammika Leshan Wannigama (ORCID: https://orcid.org/0000-0001-6316-1221)
- Cameron Hurst (ORCID: https://orcid.org/0000-0002-4577-8962)
- Aisha Khatib (ORCID: https://orcid.org/0000-0001-6061-4117)
- Hitoshi Ishikawa (ORCID: https://orcid.org/0000-0002-0046-9787)
- Kyoji Moriya
- Yoshitaka Shimotai (ORCID: https://orcid.org/0000-0002-9612-3261)
- Mika Moriya
- Daisuke Sano (ORCID: https://orcid.org/0000-0001-8075-6972)
- Hiroshi Hamamoto (ORCID: https://orcid.org/0000-0001-9315-7442)
- Hirotake Mori (ORCID: https://orcid.org/0000-0002-7988-5758)
- Shuichi Abe
- Kazuhiko Miyanaga (ORCID: https://orcid.org/0000-0002-3483-9491)
- Naveen Kumar Devanga Ragupathi (ORCID: https://orcid.org/0000-0001-8667-7132)
- Kenji Shibuya (ORCID: https://orcid.org/0000-0003-2528-7530)
- Paul G. Higgins (ORCID: https://orcid.org/0000-0001-8677-9454)
- Takashi Furukawa (ORCID: https://orcid.org/0000-0001-5019-2264)
- Yu Suzuki (ORCID: https://orcid.org/0000-0003-4688-4334)
- Taichi Adachi
- Daisuke Akaneya
- Daisuke Ishizawa
Institutions
- Thammasat University (TH)
- Yamagata University (JP)
- Jichi Medical University (JP)
- University of Auckland (NZ)
- Chulalongkorn University (TH)
- The Kids Research Institute Australia (AU)
- The University of Western Australia (AU)
- University of Cologne (DE)
- University of Toronto (CA)
- Tohoku University (JP)
- Curtin University (AU)
- Princess Margaret Hospital for Children (AU)
- King Chulalongkorn Memorial Hospital (TH)
- Sri Lanka Law College (LK)
- Juntendo University (JP)
- Chulabhorn Hospital (TH)
- German Center for Infection Research (DE)
- Yamagata Prefectural Central Hospital (JP)
- Foundation for Advanced Studies on International Development (JP)
- University Hospital Cologne (DE)
- Kitasato University (JP)
- University of Sheffield (GB)
- Yamagata Prefectural University of Health Sciences (JP)
Publication Details
- Journal
- Drug Discoveries & Therapeutics
- Published
- 2025-10-15
- DOI
- https://doi.org/10.5582/ddt.2025.01070
- Primary Topic
- Parasites and Host Interactions
- Type
- article
- Field-Weighted Citation Impact
- 0.00
Funders
- Japan Society for the Promotion of Science