Occurrence and genetic variability of Kemerovo virus in Ixodes ticks from different regions of Western Siberia, Russia and Kazakhstan.

Kemerovo virus (KEMV), a member of the Reoviridae family, Orbivirus genus, is transmitted by Ixodes ticks and can cause aseptic meningitis and meningoencephalitis. Recently, this virus was observed in certain provinces of European part of Russia, Ural, and Western and Eastern Siberia. However, the occurrence and genetic diversity of KEMV in Western Siberia remain poorly studied. Therefore, the aim of this work was to investigate the prevalence and genetic variability of KEMV in Ixodes ticks from Western Siberia. A total of 1958 Ixodes persulcatus, I. pavlovskyi ticks and their hybrids from Novosibirsk and Omsk provinces, Altai Republic (Russia) and East Kazakhstan province (Kazakhstan) were analyzed for the presence of KEMV and tick-borne encephalitis virus (TBEV) RNA. It was observed that the KEMV distribution area in Western Siberia was wider than originally thought and included Northern and Northeastern Altai in addition to the Omsk and Novosibirsk provinces. For the first time, this virus was found in Kazakhstan. The occurrence of KEMV was statistically lower than TBEV in most locations in Western Siberia. KEMV was found both in I. persulcatus and I. pavlovskyi ticks and in their hybrids. Notably, KEMV variants observed in the 2010s were genetically different from those isolated in the 1960s, which indicated the ongoing process of evolution of the Kemerovo virus group. Moreover, the possibility of reassortment for KEMV was demonstrated for the first time.