Trichinella T9 in wild bears in Japan: Prevalence, species/genotype identification, and public health implications

Masaki Murakami; Toshihiro Tokiwa; Hiromu Sugiyama; Mitsuko Shiroyama; Yasuyuki Morishima; Sota Watanabe; Takato Sasamori; Mami Kondo; Tsutomu Mano; Hifumi Tsuruga

doi:10.1016/j.ijppaw.2023.07.002

Trichinella T9 in wild bears in Japan: Prevalence, species/genotype identification, and public health implications

Int J Parasitol Parasites Wildl. 2023 Jul 4:21:264-268. doi: 10.1016/j.ijppaw.2023.07.002. eCollection 2023 Aug.

Authors

Masaki Murakami^{1

2}, Toshihiro Tokiwa¹, Hiromu Sugiyama^{2

3}, Mitsuko Shiroyama³, Yasuyuki Morishima², Sota Watanabe⁴, Takato Sasamori⁵, Mami Kondo⁶, Tsutomu Mano⁷, Hifumi Tsuruga⁷

Affiliations

¹ Laboratory of Veterinary Parasitology, Nippon Veterinary and Life Science University, Musashino, Tokyo, 180-8602, Japan.
² Laboratory of Helminthology, Department of Parasitology, National Institute of Infectious Diseases, Shinjuku, Tokyo, 162-8640, Japan.
³ School of Life and Environmental Science, Azabu University, Sagamihara, Kanagawa, 252-5201, Japan.
⁴ Graduate School of Arts and Science, Iwate University, Morioka, Iwate, 020-8550, Japan.
⁵ Agriculture, Forestry and Fisheries Division, Fukaura Town Office, Fukaura, Aomori, 038-2324, Japan.
⁶ Nature Conservation Division, Department of Living and Environment, Akita Prefectural Office, Akita, Akita, 010-8570, Japan.
⁷ Research Institute of Energy, Environment and Geology, Industrial Technology and Environment Research Department, Hokkaido Research Organization, Sapporo, Hokkaido, 060-0819, Japan.

Abstract

In Japan, the recent series of sporadic outbreaks of human trichinellosis caused by Trichinella (Nematoda: Trichocephalida) has occurred owing to the consumption of raw or insufficiently cooked meat from wild bears. However, the infection status and molecular characteristics of Trichinella larvae in Japanese wild bears remain poorly understood. This study investigated the prevalence of Trichinella spp. in brown bears (Ursus arctos) from Hokkaido, and Japanese black bears (Ursus thibetanus japonicus) from three prefectures (Aomori, Akita, and Iwate) in northern Japan, between April 2019 and August 2022. Trichinella larvae were detected in 2.5% (6/236) of the brown bears and 0.9% (1/117) of the Japanese black bears. Sequence analysis using two genetic loci, the internal transcribed spacer region of nuclear ribosomal DNA and the mitochondrial cytochrome c oxidase subunit I gene, revealed that the larvae collected from the seven infected bears were identical to one of the two haplotypes of Trichinella T9. The prevalence of Trichinella T9 is low but is maintained in bears in the Hokkaido and Iwate prefectures suggesting that undercooked meat from these animals could cause human infection. Thus, continued health education campaigns are needed to raise awareness of the potential risk of trichinellosis among hunters, meat suppliers, consumers, and local governmental health agencies.

Keywords: Bear; Game meat; Public health; Trichinella; Ursus arctos; Ursus thibetanus japonicus.