Search

A tick-borne encephalitis virus focus was identified in a former goat pasture that had been associated with a milk-borne encephalitis outbreak in 2007. Ticks and rodents were sampled monthly from April 2010 to October 2013 on two separate 0.5 ha sampling sites. At site 1, three tick-borne encephalitis virus strains were isolated from a total of 7,247 sampled ticks; 28 of the 539 tested sera (5.19%) were seropositive. At site 2, from the 2,369 sampled ticks, virus was not isolated, tests of 284 rodent sera resulted in 14 positives (4.93%). For survival, the virus needs a territory with continuously dense rodent and tick population, although observed TBEV prevalence was low both in ticks and in rodents. Sampling points of positive ticks and rodents did not coincided exactly, at a certain time only some m territory is dangerous, these hot spots change unpredictably as positive ticks die or move on with their hosts. [ABSTRACT FROM AUTHOR]

Four tick-borne encephalitis virus strains were isolated from a small 0.5-ha focus over a six-year-long period (2011-2016) in Hungary. Two strains with identical genomes were isolated from Ixodes ricinus and Haemaphysalis concinna two months apart, which shows that the virus had not evolved separately in these tick species. Whole-genome sequencing of the virus revealed that the isolates differed from each other in 4 amino acids and 9 nucleotides. The calculated substitution rates indicated that the speed of genome evolution differs from habitat to habitat, and continuously changes even within the same focus. The amino acid changes affected the capsid, envelope, NS2a and NS5 genes, and one mutation each occurred in the 5' and 3' NCR as well as the premembrane, NS2a and NS5 genes. Phylogenetic analyses based on complete coding ORF sequences showed that the isolates belong to the European subtype of the virus and are closely related to the Finnish Kumlinge strains, the Bavarian isolate Leila and two isolates of Russian origin, but more distantly related to viruses from the neighbouring Central European countries. These isolates obviously have a common origin and are probably connected by migrating birds. These are the first published complete Hungarian TBEV sequences., (Copyright © 2018. Published by Elsevier GmbH.)

Rodents captured in a known tick-borne encephalitis virus (TBEV) focus were serologically surveyed for 4 years, with 28 visits. The collected sera were analysed by virus neutralization test. Bank vole (Myodes glareolus) had a significantly higher incidence rate of antibodies to TBEV (20.5%) than Apodemus flavicollis (3.7%) and Apodemus agrarius (4.6%). In all species, rates were higher in adults (6.8%) than in juveniles (1.7%). A higher incidence rate was observed in female A. flavicollis individuals (6.7%) than in males (1.5%). Smaller bank vole population coincided with lower (1.2-4.8%) seropositivity in all small rodents, while more abundant bank vole population meant higher (17.9%) total seropositivity. The TBEV focus originally had only Apodemus mice, bank voles appeared later, reached 20.5% positivity and raised the positivity in small rodents from 4% to 10.2% in 3 years. The results highlight the role of M. glareolus and of adult rodents in maintaining the TBEV in nature.