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. 2022 Oct 26;14(11):2362.
doi: 10.3390/v14112362.

Tick-Borne Encephalitis Virus Prevalence in Sheep, Wild Boar and Ticks in Belgium

Nadjah Radia Adjadj  1 , Muriel Vervaeke  2 , Charlotte Sohier  1 , Mickaël Cargnel  3 , Nick De Regge  1
Affiliations

Tick-Borne Encephalitis Virus Prevalence in Sheep, Wild Boar and Ticks in Belgium

Nadjah Radia Adjadj et al. Viruses. .

Abstract

Tick-borne encephalitis virus (TBEV) is the most important tick-borne zoonotic virus in Europe. In Belgium, antibodies to TBEV have already been detected in wildlife and domestic animals, but up-to-date prevalence data for TBEV are lacking, and no studies have assessed its seroprevalence in sheep. Serum samples of 480 sheep from all over Belgium and 831 wild boar hunted in Flanders (northern Belgium) were therefore screened for TBEV antibodies by ELISA and plaque reduction neutralization test (PRNT), respectively. The specificity of positive samples was assessed by PRNTs for TBEV and the Louping Ill, West Nile, and Usutu viruses. TBEV seroprevalence was 0.42% (2/480, CI 95%: 0.11-1.51) in sheep and 9.27% (77/831, CI 95%: 7.48-11.43) in wild boar. TBEV seroprevalence in wild boar from the province of Flemish Brabant was significantly higher (22.38%, 15/67) compared to Limburg (7.74%, 34/439) and Antwerp (8.61%, 28/325). Oud-Heverlee was the hunting area harboring the highest TBEV seroprevalence (33.33%, 11/33). In an attempt to obtain a Belgian TBEV isolate, 1983 ticks collected in areas showing the highest TBEV seroprevalence in wild boars were tested by real-time qPCR. No TBEV-RNA-positive tick was detected. The results of this study suggest an increase in TBEV prevalence over the last decade and highlight the need for One-Health surveillance in Belgium.

Keywords: Belgium; PRNT; prevalence; sheep; tick-borne encephalitis; ticks; wild boar.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Geographical repartition of sheep samples (indicated with blue circles). The 10 Belgian provinces are indicated in bold. WVL: West Flanders, OVL: East Flanders, ANT: Antwerp, LIM: Limburg, VBR: Flemish Brabant, WBR: Walloon Brabant, HNT: Hainaut, NAM: Namur, LG: Liege, LUX: Luxembourg. The size of the blue circle corresponds to the number of samples per farm (from 1 to 13 samples).
Figure 2
Figure 2
Geographical repartition of the 50 wild boar hunting spots where sera were collected between May 2019 and October 2020. The 5 Flemish provinces are indicated in bold. WVL: West Flanders, OVL: East Flanders, ANT: Antwerp, LIM: Limburg, VBR: Flemish Brabant. The 4 isolated spots in the bottom right (Teuven, Remersdaal, Saint-Pieters Voeren, and Sint-Martens Voeren) belong to the province of Limburg.
Figure 3
Figure 3
Geographical repartition of the 13 (out of 480) TBEV-positive and borderline sheep serum samples according to ELISA. WVL: West Flanders, OVL: East Flanders, ANT: Antwerp, LIM: Limburg, VBR: Flemish Brabant, WBR: Walloon Brabant, HNT: Hainaut, NAM: Namur, LG: Liege, LUX: Luxembourg.
Figure 4
Figure 4
TBEV seroprevalence in wild boar sera per province. The hunting spots are indicated by green dots. The pie chart depicts the percentage of positive and negative samples per province. Tick collection sites are indicated with a red star.
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