Ixodid ticks and tick-borne encephalitis virus prevalence in the South Asian part of Russia (Republic of Tuva)

The most significant processes of arbovirus evolution can be expected to occur in the territories where ticks of different species cohabitate and at the boundaries of virus occurrence, where the probability of the appearance of new virus variants is high due to the possible shift in the main vectors and/or vertebrate hosts. One of the most interesting regions in this regard is the Republic of Tuva. Since most of its territory is covered by mountain ranges and intermountain basins, we were able to study the distribution of vectors and viruses in geographically isolated areas at different altitudes and in various landscapes. From 2008 to 2017, we conducted six expeditions to Tuva and collected 3,077 adult ticks and 24 nymphs. The distribution of tick species was confined to specific landscapes, as follows: Dermacentor nuttalli occurred in steppes, D. silvarum inhabited forest-steppe areas, and Ixodes persulcatus inhabited mixed forests. All three species of ticks were collected on plains and mountain slopes. The range of D. silvarum was shown to be lower than 1300 m above sea level (a.s.l.). Only D. nuttalli and I. persulcatus were collected at higher altitudes. According to our observations, single nymphs of D. nuttalli appear on animals one month before larvae appear. This finding confirms the hypothesis that the immature forms of D. nuttalli are able to overwinter under favourable conditions. We isolated 9 strains and 3 isolates of tick-borne encephalitis virus (TBEV) from I. persulcatus, one strain from D. nuttalli and one strain from D. silvarum. The TBEV strain from D. nuttalli was isolated from the territory inhabited only by Dermacentor ticks. All isolated strains belong to the Siberian subtype of TBEV. TBEV was detected in ticks from all the investigated altitudes. There were no statistically significant differences in the virus prevalence between the Dermacentor and Ixodes ticks. The results of our work provide additional support for the hypothesis of the existence of TBEV foci in areas with an absolute dominance of D. nuttalli. © 2019 The Authors

Kholodilov I.1 , Belova O.1, 2 , Burenkova L.1 , Korotkov Y.1 , Romanova L.1, 3 , Morozova L. 4 , Kudriavtsev V.1 , Gmyl L.1 , Belyaletdinova I.1 , Chumakov A.5 , Chumakova N.5 , Dargyn O.6 , Galatsevich N.5 , Gmyl A.1 , Mikhailov M.7 , Oorzhak N.8 , Polienko A.1 , Saryglar A.8 , Volok V. 1, 9 , Yakovlev A.1 , Karganova G.1, 3
Elsevier GmbH
  • 1 Chumakov Institute of Poliomyelitis and Viral Encephalitides (FSBSI “Chumakov FSC R&D IBP RAS), prem. 8, k.17, pos. Institut Poliomyelita, poselenie Moskovskiy, Moscow, 108819, Russian Federation
  • 2 Martsinovsky Institute of Medical Parasitology, Tropical and Vector Borne Diseases, Sechenov University, Malaya Pirogovskaya st., 20-1, Moscow, 119435, Russian Federation
  • 3 I.M. Sechenov First Moscow State Medical University of the Ministry of Health of the Russian Federation (Sechenov University), Trubetskaya st., 8-2, Moscow, 119991, Russian Federation
  • 4 Department of Tropical Medicine and Parasitic Diseases, Sechenov University, Trubetskaya st., 8-2, Moscow, 119991, Russian Federation
  • 5 Tuvinian Antiplague Station of Rospotrebnadzor, Moskovskaya st., 13, Kyzyl, 667010, Russian Federation
  • 6 Tuva Republican Center for Disease Prevention and Control of AIDS and Infectious disease, Oyuna Kursedi st., 159A, Kyzyl, 667003, Russian Federation
  • 7 I. Mechnikov Research Institute of Vaccines and Sera of the Russian Academy of Medical Sciences, Malyy Kazennyy pereulok, 5a, Moscow, 105064, Russian Federation
  • 8 Infectious disease hospital, Chekhova st., 65, Kyzyl, 667003, Russian Federation
  • 9 Peoples' Friendship University of Russia (RUDN University), Miklukho-Maklaya st., 6, Moscow, 105064, Russian Federation
Ключевые слова
Altitude; Dermacentor nuttalli nymphs; Dermacentor ticks; Ixodes persulcatus; Overwintering; TBEV steppe foci; Tick-borne encephalitis virus
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