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. 2025 Apr 3;17(4):521.
doi: 10.3390/v17040521.

Impact of BTV-3 Circulation in Belgium in 2024 and Current Knowledge Gaps Hindering an Evidence-Based Control Program

Virginie Van Leeuw  1 , Ilse De Leeuw  2 , Nicolas Degives  3 , Pieter Depoorter  1 , Jeroen Dewulf  4 , Jean-Baptiste Hanon  3 , Jozef Hooyberghs  1 , Annick Linden  5 , Laura Praet  1 , Marc Raemaekers  1 , Claude Saegerman  5 , Xavier Simons  3 , Charlotte Sohier  2 , Norbert Steurbaut  6 , Amandine Sury  1 , Etienne Thiry  7 , Stephan Zientara  8 , Axel Mauroy  1 , Nick De Regge  2
Affiliations

Impact of BTV-3 Circulation in Belgium in 2024 and Current Knowledge Gaps Hindering an Evidence-Based Control Program

Virginie Van Leeuw et al. Viruses. .

Abstract

Between 2006 and 2010, northwestern Europe experienced its first significant bluetongue virus (BTV) outbreak, driven by the spread of BTV-8, which had major repercussions on the European livestock sector. While BTV-3 was first identified in Europe in Italy in 2017, a new introduction of the virus was reported in 2023, in the Netherlands, and subsequently spread rapidly across the continent. A limited number of BTV-3 outbreaks were notified in Belgium in 2023, leading to the loss of its BTV-free status. In the following year, 2024, the virus spread throughout the country in a short time period. This study describes the impact of BTV-3 circulation in Belgium in 2024, detailing both its geographic spread and the associated increase in mortality, reduced births recorded, and decline in milk production among ruminants. Furthermore, preliminary results on the effectiveness of field vaccination and maternal immunity transfer are presented, as well as critical gaps that hinder the development of a robust, evidence-based management strategy. As the epidemiological situation is expected to become more complex in the future, due to the co-circulation of multiple BTV serotypes and other Culicoides-borne diseases, such as EHDV, effective collaboration and communication among stakeholders and international authorities will be crucial for implementing measures to mitigate the spread of these diseases.

Keywords: animal health; bluetongue; epidemiology; vaccination; vector-borne disease; virology.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Figure 1
Figure 1
Evolution of the distribution of BTV-3 outbreaks reported in Belgium between 15 July 2024, and 1 October 2024 and evolution of the number of outbreaks recorded per week between week 28 (8 July 2024 to 14 July 2024) and week 40 (30 September 2024 to 6 October 2024), based on tests sent for clinical suspicion of BTV cases (Sciensano Institute, NRL for bluetongue disease, available at https://moriskin.sciensano.be/shiny/bluetongue/, accessed on 26 March 2025).
Figure 2
Figure 2
Monthly small ruminant mortality rate recorded in Belgium between 2021 and 2024 and monthly mortality mean for 2021 to 2023.
Figure 3
Figure 3
Monthly cattle mortality rate recorded in Belgium between 2021 and 2024 and monthly recorded mortality mean for 2021 to 2023.
Figure 4
Figure 4
Monthly number of newborn calves registered in Belgium between 2021 and 2024 and monthly mean for the years 2021 to 2023 (SANITEL).
Figure 5
Figure 5
Monthly milk deliveries in Belgium between 2021 and 2024 and mean for the years 2021 to 2023 (from BCZ/CBL, https://bcz-cbl.be/sites/default/files/2025-02/Melkleveringen_12_NL.pdf; https://bcz-cbl.be/sites/default/files/2023-10/melkeveringen_2021_nl.pdf, accessed on 26 March 2025).
Figure 6
Figure 6
ELISA (A) and VNT (B) results after sheep primo vaccination with Syvazul, primo and booster Syvazul and primo Syvazul and booster Bultavo.
Figure 7
Figure 7
ELISA (A) and VNT (B) results of ewes and lambs.
See this image and copyright information in PMC

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