Molecular epidemiology of Crimean-Congo hemorrhagic fever virus in Russia.

In this report, we present new data on the diversity and geographical distribution of genetic variants in Crimean-Congo hemorrhagic fever virus (CCHFV) in Russia. Partial S, M, and L segment sequences of the CCHFV genome were obtained from 500 serum samples from CCHF patients and 103 pools of ticks collected in the south of the European region of Russia in 2007-2017. The investigated viral strains belonged to the lineages Europe 1 (596 samples), Africa 3 (1 sample) and a new genetic lineage, Europe 3 (6 samples). The Russian CCHFV strains of the Europe 1 lineage formed four subgroups (Va-Vd) correlated with the geographical site of virus isolation. Segment reassortment events between strains of different subgroups within lineage Europe 1 were revealed. The complete S, M and L genome segments of 18 CCHFV strains belonging to different subgroups of the Europe 1 lineage and the complete S segments of 3 strains of the Europe 3 lineage and 1 strain of the Africa 3 lineage were sequenced. The analysis of the geographical distribution of CCHFV genetic variants in southern Russia revealed local viral populations with partially overlapping boundaries.

Detection of Crimean-Congo hemorrhagic fever virus in ticks collected from South Russia.

Crimean-Congo hemorrhagic fever (CCHF) has a central role among tick-borne infections in southern Russia. Multiple cases of disease are recorded annually in most regions with the СCHF foci; moreover, an expansion of the geographic range of the disease has been noted. Since 1999, more than 2300 people have fallen ill in Russia. Ticks are the main vectors and reservoirs of the Crimean-Congo hemorrhagic fever virus (CCHFV). As it is currently known, CCHFV has been detected in ticks of 33 species. In the period 2012-2019 in the south of the European part of Russia, more than 38,000 ticks of 14 species of the genera Hyalomma, Rhipicephalus, Dermacentor, Haemaphysalis and Ixodes were tested for the presence of CCHFV. Among 4,188 tick pools studied, the virus was detected in 252 (6%). The main vector, as expected, is H. marginatum (81% of positive pools). The same species is the most numerous among the studied ticks (66%). Apart from H. marginatum, the virus was detected in the following species: H. scupense, R. rossicus, R. turanicus, R. bursa, R. annulatus, D. marginatus, Haem. punctata and Ixodes ricinus. Most of the positive results were obtained from ticks collected from vertebrate hosts. As for H. marginatum, R. rossicus, D. marginatus, and Haem. punctata, the virus was detected in questing unfed specimens collected from vegetation and soil surface, which indicates the participation of these ticks in the circulation of the virus.