title: Isolation and molecular characterization of a tick-borne encephalitis virus strain from a new tick-borne encephalitis focus with severe cases in Bavaria, Germany.
abstract: Tick-borne encephalitis (TBE) is the most important viral infection transmitted by ticks in Central Europe. In Germany, where TBE was classified as a notifiable disease in 2001, a highly variable number of clinically apparent human cases was reported in the last few years, ranging from the lowest number of 238 in 2007 to a maximum of 546 in 2006. The dynamics of the virus and its vector tick remain poorly understood. We investigated a highly active TBE focus in south-eastern Germany where from 2003 to 2008 a total of 9 clinical human cases was diagnosed. Three out of these 9 cases were fatal indicating an unusually high mortality rate possibly due to a highly virulent TBEV strain. From 2005 till 2008, 2150 Ixodes ricinus ticks were collected and tested for the presence of TBE virus. Five TBEV-positive ticks were detected by real-time RT-PCR. A viable virus strain was isolated from one of the positive ticks sampled in 2005. This is the first TBE virus isolate from a tick in Germany for 30 years. Sequencing of the full-length genome of this virus strain (AS33) revealed 2 unique amino acid substitutions in the envelope protein known to play a role in the pathogenicity of TBE virus. Amplification of the envelope gene using 2 TBEV-PCR-positive ticks from 2006 also showed these particular mutations indicating that this TBE virus strain was present in at least 2 consecutive years. The entire sampling area was divided into smaller sectors for the exact location of TBEV-positive ticks. Virus-positive ticks were found to be randomly distributed throughout the investigated focus, which is used as recreational area by the local people.
authors.affiliation: Institute of Comparative Tropical Medicine and Parasitology, Ludwig Maximilian University, Leopoldstr. 5, 80802 Munich, Germany.
authors.forename: Anne M
authors.initials: AM
authors.lastname: Kupča
authors.forename: Sandra
authors.initials: S
authors.lastname: Essbauer
authors.forename: Gudrun
authors.initials: G
authors.lastname: Zoeller
authors.forename: Philippe G
authors.initials: PG
authors.lastname: de Mendonça
authors.forename: Roland
authors.initials: R
authors.lastname: Brey
authors.forename: Monika
authors.initials: M
authors.lastname: Rinder
authors.forename: Kurt
authors.initials: K
authors.lastname: Pfister
authors.forename: Martin
authors.initials: M
authors.lastname: Spiegel
authors.forename: Bastian
authors.initials: B
authors.lastname: Doerrbecker
authors.forename: Martin
authors.initials: M
authors.lastname: Pfeffer
authors.forename: Gerhard
authors.initials: G
authors.lastname: Dobler
mesh_terms: D000818:Animals; D002522:Chlorocebus aethiops; D004669:Encephalitis Viruses, Tick-Borne / Q000145:classification* / Q000235:genetics*; D004675:Encephalitis, Tick-Borne / Q000453:epidemiology* / Q000401:mortality / Q000821:virology*; D015967:Gene Expression Regulation, Viral / Q000502:physiology; D005858:Germany / Q000453:epidemiology; D006801:Humans; D018884:Ixodes / Q000821:virology*; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014709:Vero Cells; D014759:Viral Envelope Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D012336:RNA, Ribosomal, 16S; D014759:Viral Envelope Proteins