Molecular Detection and Serological Evidence of Tick-Borne Encephalitis Virus in Serbia

Tick-borne encephalitis (TBE) is a zoonotic flaviviral infection that is a growing public health concern in European countries. The aims of this research were to detect and characterize tick-borne encephalitis virus (TBEV) in Ixodes ricinus ticks at presumed natural foci in Serbia, and to determine seroprevalence of TBEV IgG antibodies in humans and animals. A total of 500 I. ricinus ticks were examined for the presence of TBEV by real-time RT-PCR, and conventional nested PCR and sequencing. To determine TBEV seroprevalence, 267 human sera samples were collected, as were 200 sera samples from different animal species. All sera samples were examined by ELISA for the presence of anti-TBEV antibodies. To exclude cross-reactivity, all sera samples were tested for anti-West Nile virus (WNV) antibodies and all human sera samples were also tested for anti-Usutu virus antibodies by ELISA. Results of this preliminary study indicated TBEV activity in Serbia at two microfoci. Several decades after the previous documentation of TBEV in Serbia, we have demonstrated the presence of TBEV in I. ricinus questing nymphs (prevalence 2% and 6.6% at the two different localities) and anti-TBEV antibodies in humans (seroprevalence 0.37%). Moreover, we show for the first time TBEV seroprevalence in several animal species in Serbia, including dogs (seroprevalence 17.5%), horses (5%), wild boars (12.5%), cattle (2.5%), and roe deer (2.5%). None of the goats tested was positive for anti-TBEV IgG antibodies. TBEV isolate from I. ricinus tick in this study belonged to the Western European subtype. To understand the true public health concern in Serbia, detailed epidemiological, clinical, virological, and acarological research are required. This is important for implementation of effective control measures to reduce the incidence of TBE in Serbia.