Investigation of the tick-borne encephalitis virus in Norway

Abstract

Expansion of the range of Ixodes ricinus ticks further north and to higher altitudes affects the spread of tick-borne encephalitis virus (TBEV) in new territories and increases the risk of human infections. Over the past decade, the number of tick-borne encephalitis (TBE) cases has increased in Norway and parts of the southern coast have been established as endemic. The aims of this study were to confirm the existence of TBEV endemic foci, determine the spread of TBE in different localities of Norway, review and compare relevant published records on the prevalence of TBEV in the different developmental stages and sex of the ticks. Ticks were collected from nine locations along the southern coast of Norway during June-July 2009. For the detection of TBEV-specific RNA, a real-time RT-PCR targeting a part of the 3’ non-coding region of the TBEV genome was used. A total of 1542 ticks grouped in 250 pools were examined and TBEV RNA was detected in 5 pools with overall prevalence of 0.32%.