Bai et al.
Discovery of tick-borne Karshi virus implies misinterpretation of tick-borne encephalitis virus seroprevalence in northwest China
Front Microbiol. 2022;13:872067. doi: 10.3389/fmicb.2022.872067

The study discussed here is dealing with Karshi virus (KSIV). This virus was first isolated from soft ticks in Uzbekistan in 1972, and later, it was described in Hyalomma and soft ticks in Central Asia (Alma-Ata region and Turkmenistan). Now, it has been found in various ticks (H. detritum/scupense, H. asiaticum and Dermacentor nuttali) in Northwestern China (Xinjiang).

KSIV belongs to the family of Flaviviridae and is a member of the TBE virus serocomplex group. The strain isolated in Northwestern China has 69.7%–71.7% amino acid and 67.1%–67.9% nucleotide identity to those of other viruses in this group, with the highest to that of TBE virus with 67.9% for nucleotide and 71.7% for amino acid sequence.

KHIS can infect various human and animal cell lines, including tick cell lines, but not the mosquito cell line C6/36.

6-week-old C5BL/6 mice, experimentally infected with KSIV, did not show any signs of illness. but 2- and 9-day-old suckling mice became ill, and death occurred at day 7 post-infection.

Seroprevalence studies showed positivity for KSIV in domestic sheep, and wild animals (marmot), but not in great gerbils and long-tailed ground squirrels.

Polyclonal KSIV serum cross-reacted with TBE virus and antibodies against TBE virus cross-reacted with KSIV. This cross-reactivity was also shown in neutralization assays.

In Northwestern China (Tianshan Mountains and Altay Mountains), high seroprevalence for TBE virus had been documented since the 1990s, but in contrast, only a few TBE cases had been recorded. The authors speculated that there might have been a misinterpretation of the high TBE virus seroprevalence due to the cross-reactivity with KSIV and proposed more detailed investigations in the prevalence of both viruses in that region.

KSIV may be a pathogen for a variety of animals as well as for humans, and the results presented here may enhance the preparation to provide medical care against emerging diseases such as KSIV.

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