Bai et al.
Identification and characterization of new Siberian subtypes of tick-borne encephalitis virus isolates revealed genetic variations of the Chinese strains. Infect. Genet. Evol. 2024; 124:105660. doi:10.1016/j.meegid.2024.105660
Between 2007 and 2018, 3,364 cases of TBE were reported in China, with most occurring in the northeast. There are limited data available regarding the epidemiology and phylogeny of TBE virus strains from Inner Mongolia.
A total of 6990 questing ticks were collected in Inner Mongolia. TBE virus could be isolated from Ixodes persulcatus, Haemaphysalis concinna, and Dermacentor silvarum. The new strains were isolated from ticks by inoculating suckling mice with tick homogenates. This was followed by passages using cell lines incubated with brain homogenates from TBE virus-infected mice or tick homogenates.
Whole genome sequencing was carried out and phylogenetic trees based on the ORF sequences showed that four strains clustered with the Far Eastern subtype. Two other strains were classified as belonging to the Siberian subtype – the first Siberian subtype strain isolated in northeastern China. It was suggested that all Chinese TBE virus strains were the result of wildlife migration including migratory birds from Russia and Kazakhstan. Hulun Buir and Mudanjing, regions in northeastern China and bordering Mongolia and Russia, were considered hotspots with multiple import and export routes for Chinese TBE virus strains.
Prior to this study, the first and only Siberian subtype TBE virus strain had been isolated from I. persulcatus in Xingjang, northwestern China. The detection of two virus isolates of the Siberian subtype in Inner Mongolia suggests the emergence of this subtype in northeastern China.