Adjadj et al.
Tick-borne encephalitis virus prevalence in sheep, wild boar and ticks in Belgium.
Viruses. 2022;14(11):2362. doi:10.3390/v14112362

In Belgium, only a few TBE cases have so far been reported in humans (see, e.g., Snapshot week 24/2021). However, seroepidemiological data generated between 2011 and 2016 revealed that TBE virus may be more widely distributed because TBE antibody prevalence in cattle, wild boar, roe deer and dogs was found to range from 0.11% to 5.1%. A new antibody seroprevalence study has now been carried out in wild boar and sheep to detect TBE virus in ticks across Belgium.

All Belgian provinces (n=10) were included in a study to determine the prevalence of TBE antibodies in sheep (a total of 480 samples). In addition, a total of 831 blood samples from wild boar hunted in northern Belgium were analyzed.

Three samples of sheep sera were TBE ELISA positive and 10 samples were borderline. None of the ELISA-positive samples were positive in a neutralization assay, but two of the borderline samples were confirmed positive. Out of 831 blood samples from hunted wild boars, 142 samples were ELISA positive. Further analysis in neutralization assay revealed a positivity rate between 4.35% and 14.20% in various locations.

In areas with the highest TBE antibody prevalence in wild boars, a total of 1983 ticks were collected, and 408 pools were analyzed for TBE virus-specific RNA by qPCR. No TBE virus-positive ticks were detected.

The increase of TBE antibody positivity in wild boars over the last decade indicate the presence of TBE foci in Flanders (northern Belgium), although no TBE virus has so far been isolated in Belgium.

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