Tick-Borne Encephalitis Virus Diversity in Ixodid Ticks and Small Mammals in South-Western Siberia, Russia.
The persistence of tick-borne encephalitis virus (TBEV) in nature is maintained by numerous species of reservoir hosts, multiple transmissions between vertebrates and invertebrates, and the virus adaptation to its hosts. Our Aim: was to compare TBEV isolates from ticks and small wild mammals to estimate their roles in the circulation of the viral subtypes.



TBEV isolates from two species of ixodid ticks, four species of rodents, and one species of shrews in the Novosibirsk region, South-Western Siberia, Russia, were analyzed using bioassay, hemagglutination, hemagglutination inhibition, neutralization tests, ELISA, reverse transcription with real-time PCR, and phylogenetic analysis.



TBEV RNA and/or protein E were found in 70.9% ± 3.0% of mammals and in 3.8% ± 0.4% of ticks. The TBEV infection rate, main subtypes, and neurovirulence were similar between ixodid tick species. However, the proportions of the virus that were pathogenic for laboratory mice and of the Far-Eastern (FE) subtype, as well as the viral loads with the Siberian and the European subtypes for the TBEV in Ixodes pavlovskyi Pomerantsev, 1946 were higher than in Ixodes persulcatus (P. Schulze, 1930). Percentages of infected Myodes rutilus, Sicista betulina, and Sorex araneus exceeded those of Apodemus agrarius and Myodes rufocanus. Larvae and nymphs of ticks were found mainly on rodents, especially on Myodes rufocanus and S. betulina. The proportion of TBEV-mixed infections with different subtypes in the infected ticks (55.9% ± 6.5%) was higher than in small mammals (36.1% ± 4.0%) (p < 0.01).



Molecular typing revealed mono- or mixed infection with three main subtypes of TBEV in ticks and small mammals. The Siberian subtype was more common in ixodid ticks, and the FE subtype was more common in small mammals (p < 0.001). TBEV isolates of the European subtype were rare. TBEV infection among different species of small mammals did not correlate with their infestation rate with ticks in the Novosibirsk region, Russia.
1 Institute of Systematics and Ecology of Animals of the Siberian Branch of the Russian Academy of Sciences , Novosibirsk, Russia .
Valentina N
VN
Bakhvalova
1 Institute of Systematics and Ecology of Animals of the Siberian Branch of the Russian Academy of Sciences , Novosibirsk, Russia .
Galina S
GS
Chicherina
1 Institute of Systematics and Ecology of Animals of the Siberian Branch of the Russian Academy of Sciences , Novosibirsk, Russia .
Olga F
OF
Potapova
1 Institute of Systematics and Ecology of Animals of the Siberian Branch of the Russian Academy of Sciences , Novosibirsk, Russia .
Victor V
VV
Panov
1 Institute of Systematics and Ecology of Animals of the Siberian Branch of the Russian Academy of Sciences , Novosibirsk, Russia .
Victor V
VV
Glupov
1 Institute of Systematics and Ecology of Animals of the Siberian Branch of the Russian Academy of Sciences , Novosibirsk, Russia .
Mikhail A
MA
Potapov
2 Department of Microbiology and Immunology, New York Medical College , Valhalla, New York.|3 The Rockefeller University , New York, New York.
Stephen J
SJ
Seligman
4 Ivanovsky Institute of Virology of the Federal Research Center of Epidemiology and Microbiology of N.F. Gamaleya of the Russian Ministry of Health , Moscow, Russia .|5 Federal Research Clinical Center of Physical-Chemical Medicine of the Federal Medical and Biological Agency of Russia , Moscow, Russia .
Olga V
OV
Morozova
D000818:Animals; D000831:Animals, Newborn; D004197:Disease Reservoirs; D004669:Encephalitis Viruses, Tick-Borne / Q000235:genetics* / Q000472:pathogenicity; D026863:Ixodidae / Q000382:microbiology*; D008322:Mammals / Q000382:microbiology*; D051379:Mice; D008813:Mice, Inbred ICR; D010802:Phylogeny; D012800:Siberia; D014774:Virulence
Flavivirus; Rodents; Tick(s); Tick-borne encephalitis; Transmission.