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European subtype tick-borne encephalitis virus in Ixodes persulcatus ticks.

Jääskeläinen AE, Tonteri E, Sironen T, Pakarinen L, Vaheri A, Vapalahti O - Emerging Infect. Dis. (2011)

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The northernmost tick-borne encephalitis (TBE) focus is in Simo, Finnish Lapland... Tick-borne encephalitis virus (TBEV) is transmitted by Ixodes spp. ticks and is endemic to Eurasia from central Europe to the Far East... The TBEV RNA prevalence among ticks and rodents was relatively high, as is the incidence among humans (0.57 cases/year/1,000 inhabitants) in Simo, indicating a focus with high activity... Within the 1208 nt from the E gene, Simo-38 and Simo-48 from ticks and Simo-9 from a bank vole were identical... Other sequences differed for 1 nt and Simo-2 for 1 aa compared with the others... The partial nonstructural protein 3 gene sequences were identical, and the phylogenetic tree showed similar topography as for the E gene (not shown)... The only tick species found in Simo was I. persulcatus, further widening its known distribution along the western coast of Finland (Figure A1)... However, the virus subtype found in Simo was TBEV-Eur strain, the main vector of which is the I. ricinus tick... The nearest TBE-endemic focus is the Kokkola archipelago, ≈200 km south (Figure A1), but there I. persulcatus ticks carry the TBEV-Sib strain... The nearest areas to which the TBEV-Eur strain is endemic are in southern Finland where only I. ricinus ticks have been found... An altered microclimate favoring TBE circulation, in addition to introduction of the virus, could also explain the recent emergence of TBE in Simo... In conclusion, Simo in Finnish Lapland is a new TBE-endemic focus demonstrating northward movement of foci and an unusual combination of the TBEV-Eur strain and I. persulcatus ticks in an area with no evidence of cocirculation of tick species or TBEV subtypes.

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A1. Phylogenetic tree of partial E (1172-nt) gene sequences, shwoing Ixodes ricinus–transmitted strains (red) and I. persulcatus–transmitted strains (green). The tree was reconstructed by the Bayesian Markov chain Monte Carlo method in BEAST (http://beast.bio.ed.ac.uk). Maximum clade credibility tree with an arbitrary root is shown with mean branch lengths, and Bayesian posterior probabilities are given at nodes when >0.7. Country of origin and isolation year are indicated. Four strains from Simo are shown; Simo-48 and Simo-9 were identical to Simo-38. Yellow shading, tick-borne encephalitis–endemic areas; red line, I. ricinus distribution; green line, I. persulcatus distribution; LPR, Lappeenranta. Scale bar indicates number of substitutions per site.
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FA.1: A1. Phylogenetic tree of partial E (1172-nt) gene sequences, shwoing Ixodes ricinus–transmitted strains (red) and I. persulcatus–transmitted strains (green). The tree was reconstructed by the Bayesian Markov chain Monte Carlo method in BEAST (http://beast.bio.ed.ac.uk). Maximum clade credibility tree with an arbitrary root is shown with mean branch lengths, and Bayesian posterior probabilities are given at nodes when >0.7. Country of origin and isolation year are indicated. Four strains from Simo are shown; Simo-48 and Simo-9 were identical to Simo-38. Yellow shading, tick-borne encephalitis–endemic areas; red line, I. ricinus distribution; green line, I. persulcatus distribution; LPR, Lappeenranta. Scale bar indicates number of substitutions per site.

Mentions: The transmission cycle of at least TBEV-Eur in nature is fragile and depends on microclimatic conditions. Thus, within the I. ricinus distribution area, TBE is endemic merely focally (1,2). In Finland, TBE foci are located by the sea or large lakes (Figure A1). Both vector tick species are found: I. ricinus ticks in the southern and central parts of the country, but I. persulcatus ticks are in scattered foci along the western coast, including the Kokkola archipelago and Närpiö municipality, where they carry TBEV-Sib (3,4) (Figure A1).


European subtype tick-borne encephalitis virus in Ixodes persulcatus ticks.

Jääskeläinen AE, Tonteri E, Sironen T, Pakarinen L, Vaheri A, Vapalahti O - Emerging Infect. Dis. (2011)

A1. Phylogenetic tree of partial E (1172-nt) gene sequences, shwoing Ixodes ricinus–transmitted strains (red) and I. persulcatus–transmitted strains (green). The tree was reconstructed by the Bayesian Markov chain Monte Carlo method in BEAST (http://beast.bio.ed.ac.uk). Maximum clade credibility tree with an arbitrary root is shown with mean branch lengths, and Bayesian posterior probabilities are given at nodes when >0.7. Country of origin and isolation year are indicated. Four strains from Simo are shown; Simo-48 and Simo-9 were identical to Simo-38. Yellow shading, tick-borne encephalitis–endemic areas; red line, I. ricinus distribution; green line, I. persulcatus distribution; LPR, Lappeenranta. Scale bar indicates number of substitutions per site.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3376769&req=5

FA.1: A1. Phylogenetic tree of partial E (1172-nt) gene sequences, shwoing Ixodes ricinus–transmitted strains (red) and I. persulcatus–transmitted strains (green). The tree was reconstructed by the Bayesian Markov chain Monte Carlo method in BEAST (http://beast.bio.ed.ac.uk). Maximum clade credibility tree with an arbitrary root is shown with mean branch lengths, and Bayesian posterior probabilities are given at nodes when >0.7. Country of origin and isolation year are indicated. Four strains from Simo are shown; Simo-48 and Simo-9 were identical to Simo-38. Yellow shading, tick-borne encephalitis–endemic areas; red line, I. ricinus distribution; green line, I. persulcatus distribution; LPR, Lappeenranta. Scale bar indicates number of substitutions per site.
Mentions: The transmission cycle of at least TBEV-Eur in nature is fragile and depends on microclimatic conditions. Thus, within the I. ricinus distribution area, TBE is endemic merely focally (1,2). In Finland, TBE foci are located by the sea or large lakes (Figure A1). Both vector tick species are found: I. ricinus ticks in the southern and central parts of the country, but I. persulcatus ticks are in scattered foci along the western coast, including the Kokkola archipelago and Närpiö municipality, where they carry TBEV-Sib (3,4) (Figure A1).

View Article: PubMed Central - PubMed

AUTOMATICALLY GENERATED EXCERPT
Please rate it.

The northernmost tick-borne encephalitis (TBE) focus is in Simo, Finnish Lapland... Tick-borne encephalitis virus (TBEV) is transmitted by Ixodes spp. ticks and is endemic to Eurasia from central Europe to the Far East... The TBEV RNA prevalence among ticks and rodents was relatively high, as is the incidence among humans (0.57 cases/year/1,000 inhabitants) in Simo, indicating a focus with high activity... Within the 1208 nt from the E gene, Simo-38 and Simo-48 from ticks and Simo-9 from a bank vole were identical... Other sequences differed for 1 nt and Simo-2 for 1 aa compared with the others... The partial nonstructural protein 3 gene sequences were identical, and the phylogenetic tree showed similar topography as for the E gene (not shown)... The only tick species found in Simo was I. persulcatus, further widening its known distribution along the western coast of Finland (Figure A1)... However, the virus subtype found in Simo was TBEV-Eur strain, the main vector of which is the I. ricinus tick... The nearest TBE-endemic focus is the Kokkola archipelago, ≈200 km south (Figure A1), but there I. persulcatus ticks carry the TBEV-Sib strain... The nearest areas to which the TBEV-Eur strain is endemic are in southern Finland where only I. ricinus ticks have been found... An altered microclimate favoring TBE circulation, in addition to introduction of the virus, could also explain the recent emergence of TBE in Simo... In conclusion, Simo in Finnish Lapland is a new TBE-endemic focus demonstrating northward movement of foci and an unusual combination of the TBEV-Eur strain and I. persulcatus ticks in an area with no evidence of cocirculation of tick species or TBEV subtypes.

Show MeSH