Takahashi et al.
Characterization of tick-borne encephalitis virus isolated from tick infesting dog in central Hokkaido in 2018
Ticks Tick Borne Dis. 2022; 13(2):101900. doi: 10.1016/j.ttbis.2022.101900

The first confirmed TBE case in Japan was reported in 1993 in the southern part of Hokkaido. Recently, four more human cases have been reported across Hokkaido and seroepidemiological studies in wild animals revealed the circulation of TBE virus also in other areas of Japan.

In 2018, a study was conducted, in which a total of 267 ticks were collected from dogs in 40 veterinary hospitals across Hokkaido. One TBE virus strain could be isolated from an Ixodes ovatus tick infesting a dog from central Hokkaido. 10 days after the removal of the tick, the dog had developed neutralizing antibodies.

The complete genome sequence of this TBE virus strain Nanporo-18-44 revealed that it belonged to the Far Eastern subtype but was phylogenetically different from the well-characterized strain Oshima-5-10. It was concluded that the two strains had invaded Hokkaido independently from each other from the Eurasian continent.

The pathogenicity of strain Nanporo-18-44 was compared to strain Oshima-5-10, and both strains showed a similar virulence.

TBE virus is likely extensively endemic in Japan, and the authors concluded that infections by unrecognized strains exist in humans and animals in Japan in areas other than Hokkaido.

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