Prevalence of antibodies against tick-borne encephalitis virus in wild game from Saxony, Germany

Tick-borne encephalitis (TBE) is the most important tick-transmitted viral disease in Europe and is caused by the flavivirus TBE-virus (TBEV). In Germany TBE is unevenly distributed with the vast majority of cases occurring in the south in so-called risk areas defined as regions with an incidence of at least 1 case in 100,000 inhabitants. However, in low endemic areas with lesser TBE cases the respective risk assessment is hard to achieve. We therefore intend to use the prevalence of antibodies against TBEV in wildlife to trace TBEV endemic areas as a surrogate marker for the notification of human cases. This study was conducted in Saxony, Germany, where 34 autochthonous cases were reported since 2001, thereby not allowing a geographic allocation within the state. A total of 1,851 sera from wild boar and 35 sera from roe deer from all Saxon districts shot between April 2011 and March 2013 were screened for the presence of antibodies against TBEV. The overall seropositivity for Saxony was 10.5%. Among the wild boar sera, most positive samples could be found in the districts Meißen (23%) and Vogtlandkreis (20%) followed by Dresden (18%), Erzgebirgskreis and Görlitz (both 10%). We conclude that seroprevalence studies in game animals represent a promising surrogate marker and should be considered for future determination of risk areas. Although we are currently unable to explain the discrepancy of the few human cases and the high seroprevalence in some districts, vaccination against TBE should be considered for people planning outdoor activities in Dresden, Meißen or Vogtlandkreis.