Bluetongue in Europe and Italy: old acquaintances and new scenarios 

Introduction

Bluetongue (BT) is an infectious, non-contagious disease affecting certain families within the order Artiodactyla, transmitted by blood-feeding vectors belonging to the genus Culicoides. To date, 36 BT serotypes have been identified, among which only a few are considered "atypical" due to their ability to spread through direct contact rather than via Culicoides vectors (Ries et al., 2020, 2021; The Pirbright Institute, 2015; WOAH, b).

To better understand the evolution of the disease, BTV serotypes have been classified into strains based on characteristics such as genotype, morbidity, mortality, transmission rate, and spatiotemporal distribution (More et al., 2017). Furthermore, different strains of the same BT serotype can be differentiated into topotypes, which are generally divided into eastern strains — originating from Australia and the Middle-Far East — and western strains — of African or American origin. In Europe, particularly in the Mediterranean basin, both strain types have caused outbreaks in susceptible populations (Kundlacz et al., 2019).

Historically endemic in tropical and subtropical countries, BT has spread throughout the Mediterranean and Europe since the late 1990s, facilitated by climate change and livestock trade in the era of globalization, and enabled by the presence of the vector (Maclachlan et al., 2015; WOAH, b).

Italy, located at the heart of the Mediterranean, has been affected since 2000 by multiple epidemic waves caused by different viral strains originating from neighbouring countries, including North African nations (Lorusso et al., 2013a, 2014, 2017) and, more recently, the Balkan region (Calistri et al., 2004; Lorusso et al., 2013a, 2014, 2017; Mellor, 2004; Niedbalski, Wiesław, 2022; WOAH, b).

Unexpectedly, countries such as the Netherlands, Belgium, Luxembourg, and Germany experienced their first outbreak of serotype 8 (BTV-8) in 2006, revealing the northward spread of the disease from central Europe (Faes et al., 2013; Niedbalski, Wiesław, 2022; WOAH, b).

Between 2007 and 2010 alone, BTV-8 spread to 28 European countries, resulting in over 58,000 reported outbreaks and substantial economic losses (Nicolas et al., 2018; WOAH, b).

This article aims to provide an update on current European and Italian legislation, as well as a summary of the recent epidemiological situation, with a particular focus on the years 2023–2024.

Legislation

Bluetongue virus (BTV) is a notifiable disease listed by the World Organisation for Animal Health (WOAH) in the Terrestrial Animal Health Code. Notification of BTV serotypes 1 to 24 is mandatory to the European Commission under Commission Implementing Regulation (EU) 2020/2002. This regulation defines the specific procedures and requirements for reporting Bluetongue outbreaks within the European Union (Commission Implementing Regulation – 2020/2002, 2020; WOAH, a).

Moreover, Bluetongue virus infection caused by the serotypes listed above is classified as a category C+D+E disease, as defined in Commission Implementing Regulation (EU) 2018/1882.This classification entails that EU Member States must implement surveillance programmes (category E) to monitor the presence and spread of the infection, regulate imports and intra-EU movements (category D) to prevent further transmission, and adopt measures to contain the spread in disease-free areas or those with eradication programmes in place (category C) (Commission Implementing Regulation (EU) 2018/1882, 2018).

Under the new legal framework, the EU no longer aims for immediate eradication of the disease but rather for its prevention and control. This marks a shift from the previous approach defined by Directive 2000/75/EC and its implementing rules (such as Regulation (EC) No. 1266/2007), which were focused on eradicating BT by establishing restriction zones around each outbreak. These zones—comprising protection and surveillance areas—covered a radius of at least 150 km and imposed strict conditions, including severe limitations on animal movements (Regulation – 1266/2007; Directive 2000/75/EC, 2000).

Under the current legislative framework, including Commission Implementing Regulation (EU) 2021/620, Member States are required to notify the European Commission (EC) of any territories that have been granted disease-free status. They must also report, on a voluntary basis, any areas for which an eradication programme has been submitted for listed diseases, including Bluetongue (Figure 1).


Figure 1.Areas within the European Union, as defined by Commission Implementing Regulation (EU) 2021/620, declared by Member States as having an ongoing eradication programme, as being disease-free, or for which no health status has been declared.

According to Annex VIII dated 02/08/2024 of the aforementioned regulation, updated following the 2024 season as specified in the subsequent paragraphs, Italy has declared the Autonomous Province of Bolzano and the Friuli-Venezia Giulia Region as BTV-free zones. Moreover, no eradication program for this disease has been submitted.

The Aosta Valley is no longer listed among the BTV-free areas, as two outbreaks (serotype 8) were detected in September 2024, resulting in the suspension of its disease-free status.

Moreover, no eradication programme has been submitted by Italy for this disease.

In line with European and national legislation, the Italian Ministry of Health, in coordination with the National Reference Laboratory for Bluetongue, has issued guidelines on control and management measures at the national level, as well as on serological and entomological surveillance activities, in order to harmonise operational procedures across the National Health Service.

Given the complex epidemiological situation that developed during the summer months of 2024 due to the viral circulation of serotype 8 in mainland Italy, on 5 September 2024 the Ministry of Health deemed it appropriate to issue note no. 26696/2024. This document, intended to support the previously established control measures, introduces more stringent provisions following the notification of outbreaks, such as:

  • Clinical inspections in sheep holdings located within a 20 km radius of the confirmed outbreak, with the aim of identifying the extent of viral circulation. This is based on an expected prevalence of 2% with a 95% confidence level.
  • Conditional movement restrictions in municipalities where viral circulation has been confirmed, with authorization for the movement of animals for breeding purposes only upon a negative PCR result and insect-repellent treatment within the 7 days prior to dispatch. In the case of large consignments, testing of a representative sample is allowed.

History of Bluetongue in Italy and Europe from 2010 to 2022

From 2010 to 2022, Bluetongue virus (BTV) circulation continued across the European continent, particularly involving serotypes BTV-1, BTV-3, BTV-4, and BTV-8, as reported to WAHIS by the respective countries (Figure 1). During this same period, Italy experienced the following epidemic waves: in 2013 due to BTV-1 (6,012 outbreaks) and in 2016–2017–2021 due to BTV-4 (6,820 outbreaks) (data source: Animal Disease Information System-SIMAN).

As previously mentioned, serotype 1 was reported in Italy in 2013, initially in Sardinia, then in Sicily, and eventually in mainland Italy. The following year, a strain of the same serotype was reported in Corsica, Spain, and the Algarve region of Portugal (More et al., 2017; Niedbalski, W., 2015; Sailleau et al., 2015).

In mainland France, after five years of epidemiological “silence”, BTV-8 was detected in 2015. This strain was closely related to the one identified during the 2006–2010 epidemic wave in the same country (Belbis et al., 2017; Kundlacz et al., 2019). The circulation of this BTV-8 strain persisted from 2015 to 2019, affecting not only France but also Switzerland. In 2020, additional BTV-8 outbreaks were reported in Europe, specifically in Belgium, France, Germany, Luxembourg, Spain, and Switzerland (Niedbalski, Wiesław, 2022).

In 2012, a North African strain of BTV-4 was detected in Sardinia (Lorusso et al., 2013b). In 2014, BTV-4 outbreaks were confirmed in Greece; in July of the same year, this strain of BTV-4 was first identified in southern Bulgaria, then spread throughout the country and into the Balkans, particularly Croatia, Romania, and Slovenia, and subsequently to southern Italy, Corsica, and mainland France. In the same year, another North African strain of BTV-4 was identified in Spain and Portugal (De Diego et al., 2014). Between 2016 and 2017, the same BTV-4 serotype previously identified circulated in mainland France and Corsica. In 2020, this same strain responsible for the 2014 outbreaks re-emerged in Greece, North Macedonia, Romania, Bulgaria, and Croatia (Niedbalski, Wiesław, 2022; Romero-Trancón et al., 2025).

BT in Italy and Europe from 2023

Starting in 2023, the entire European area has been marked by the emergence of serotype 3 and serotype 8.

Bluetongue virus serotype-3 was reported in Europe at the beginning of September 2023, first in the Netherlands, followed by Belgium and Germany in late September and October, and subsequently detected in the United Kingdom in late November 2023. A strain of the same serotype was reported in WAHIS not only in Austria, Denmark, and France, but also in Greece, Liechtenstein, Luxembourg, Norway, Poland, Portugal, the Czech Republic, Spain, Sweden, and Switzerland. Due to the presence of the virus, the entire territory or affected zones of countries previously recognized as free under Implementing Regulation (EU) 2021/620 lost their disease-free status.

In Italy, BTV-3 was first identified in 2017 in western Sicily and subsequently detected in Sardinia from 2018 onwards, with outbreaks characterized by limited viral circulation and few clinical cases. Since July 2024, there has been a re-emergence of viral circulation in historically affected areas of the island, with an expanded area of spread. Furthermore, in the second half of 2024, the presence of BTV-3 was also reported in mainland Italy: on 22 October, the first positive cases were detected in cattle from a farm located in the autonomous province of Trento. Subsequently, positive cases were also confirmed in other regions, both in imported animals (Emilia-Romagna, Lombardy, and Sicily) and in animals born and raised in Italy (Lazio, Tuscany, Calabria, and Sicily).

It is important to highlight that the BTV-3 strain circulating (and still circulating) in the Italian islands is of North African origin and differs from the strain currently present in Europe. Conversely, studies are still underway to determine the origin of the BTV-3 strain found in regions of mainland Italy.

The recent BTV-3 outbreaks in Europe suggest an increased virulence of the circulating strains, due to the severe clinical signs and rapid spread.

In France, a new BTV-8 strain emerged in 2023, likely of North African origin, and has been identified as the cause of clinical cases reported in the country. This strain differs from the one responsible for the 2015 epidemic (Gondard et al., 2024). At the European level, numerous BTV-8 outbreaks were reported again in 2024, starting in France and subsequently in Greece, Portugal, and Switzerland, with clinical cases in cattle and sheep.

A BTV-8 strain showing high homology with the new French strain—detected in Corsica and southern France—was also identified in Sardinia (WAHIS). Some outbreaks caused by this BTV-8 strain were already reported in 2023 and the early months of 2024, while from July onwards, a clear re-emergence of the disease was observed, with rapid spread progressively affecting the entire regional territory. On 26 July 2024, the first suspected cases of circulation in mainland Italy were reported, specifically in the Piedmont region, following the emergence of clinical outbreaks in cattle and sheep. Just one month later, in August 2024, the number of regions affected by BTV-8 infection increased from two to six. Even the Aosta Valley, previously recognized as free at the time of the AHL’s entry into force, reported BTV-8 cases in cattle, resulting in the suspension of its disease-free status. By the end of 2024, a total of 16 regions had been affected (Basilicata, Calabria, Campania, Emilia-Romagna, Lazio, Liguria, Lombardy, Marche, Piedmont, Apulia, Sardinia, Sicily, Tuscany, Trentino-Alto Adige, Aosta Valley and Veneto).

In October 2024, BTV-12 was detected for the first time in the Netherlands, representing a significant event as this serotype had never before been reported in Europe.

Figure 2, presented in the section on the European epidemiological update, illustrates the temporal pattern of viral circulation in detail.


Figure 2.Outbreaks by year and serotype from 2010 to 2024 in the European continent (data source: World Animal Health Information System-WAHIS).

Conclusions

The changing epidemiological scenario of Bluetongue at the European level is likely the result of the impact caused by the climate emergency on the environment and its components, as observed with other vector-borne diseases (such as Crimean-Congo haemorrhagic fever, tick-borne viral encephalitis, epizootic haemorrhagic disease, and West Nile virus), which have spread into temperate zones also due to global warming. Rising temperatures contribute to the extension of the vector season and, consequently, increase the ability of infected vectors to overwinter in certain areas. The disease’s endemic persistence is made possible by the so-called “overwintering” phenomenon, which promotes the early re-emergence of the infection in the spring.

Furthermore, the new regulatory framework has undoubtedly contributed to shaping the current epidemiological situation, by exempting European Union countries from the adoption of a stringent eradication-oriented strategy such as the one previously in place.

In such a dynamic epidemiological context, the pillars for the control and prevention of Bluetongue remain solid:

  • Surveillance, which—if properly implemented—enables early detection of viral circulation within a territory, supports the prevention of spread, and facilitates the application of the most appropriate control measures.
  • Control of movements of susceptible species helps reduce the long-range transmission risk to acceptable levels.
  • Above all, vaccination remains the most effective prophylactic measure for protecting susceptible species. Eradication of a specific serotype requires the immunization of at least 95% of the population for a minimum of five consecutive years (Miranda et al., 2017).

Commercial vaccines are available for the serotypes currently circulating in Europe, and several countries have already initiated immunization campaigns.

Vaccination planning may pursue various objectives, from protecting susceptible species from clinical disease to facilitating animal movement between territories of different health statuses. However, the associated costs—particularly those related to manpower and vaccine procurement—must always be taken into consideration.

Bluetongue represents a paradigm not only for the effects of climate change in creating suitable environments for vector proliferation, but also for the role of factors such as population density, geographic distribution, and animal movements in the spread of infectious diseases.

Acknowledgements

We would like to thank Drs. Francesca Dall’Acqua and Valentina Zenobio for their kind availability and the support provided. Special thanks go to Dr. Francesca Dall’Acqua for her thoughtful contribution to the critical review and enhancement of the article's content.

 

 

References

  1. Belbis, G., Zientara, S., Bréard, E., Sailleau, C., Caignard, G., Vitour, D., & Attoui, H. (2017). Bluetongue Virus: From BTV-1 to BTV-27. Advances in Virus Research, , 161. 10.1016/bs.aivir.2017.08.003
  2. Calistri, P., Giovannini, A., Conte, A., Nannini, D., Santucci, U., Patta, C., Rolesu, S., & Caporale, V. (2004). Bluetongue in Italy: Part I. Veterinaria Italiana, 40(3), 243–251. https://pubmed.ncbi.nlm.nih.gov/20419672/
  3. de Diego, A. C. P., Sánchez-Cordón, P. J., & Sánchez-Vizcaíno, J. M. (2014). Bluetongue in Spain: from the first outbreak to 2012. Transboundary and Emerging Diseases, 61(6), 1. 10.1111/tbed.12068
  4. Direttiva 2000/75/CE, (2000). http://data.europa.eu/eli/dir/2000/75/oj/ita
  5. Faes, C., van der Stede, Y., Guis, H., Staubach, C., Ducheyne, E., Hendrickx, G., & Mintiens, K. (2013). Factors affecting Bluetongue serotype 8 spread in Northern Europe in 2006: The geographical epidemiology. Preventive Veterinary Medicine, 110(2), 149–158. 10.1016/j.prevetmed.2012.11.026
  6. Gondard, M., Postic, L., Garin, E., Turpaud, M., Vorimore, F., Ngwa-Mbot, D., Tran, M., Hoffmann, B., Warembourg, C., Savini, G., Lorusso, A., Marcacci, M., Felten, A., Roux, A. L., Blanchard, Y., Zientara, S., Vitour, D., Sailleau, C., & Bréard, E. (2024). Exceptional Bluetongue virus (BTV) and Epizootic hemorrhagic disease virus (EHDV) circulation in France in 2023. Virus Research, 350, 199489. 10.1016/j.virusres.2024.199489
  7. Kundlacz, C., Caignard, G., Sailleau, C., Viarouge, C., Postic, L., Vitour, D., Zientara, S., & Breard, E. (2019). Bluetongue Virus in France: An Illustration of the European and Mediterranean Context since the 2000s. Viruses, 11(7)10.3390/v11070672
  8. Lorusso, A., Guercio, A., Purpari, G., Camm�, C., Calistri, P., D'Alterio, N., Hammami, S., Sghaier, S., & Savini, G. (2017). Bluetongue virus serotype 3 in Western Sicily, November 2017. Veterinaria Italiana, 53(4), 273–275. 10.12834/VetIt.251.520.178
  9. Lorusso, A., Sghaier, S., Ancora, M., Marcacci, M., Di Gennaro, A., Portanti, O., Mangone, I., Teodori, L., Leone, A., Camma’, C., Petrini, A., Hammami, S., & Savini, G. (2014). Molecular epidemiology of bluetongue virus serotype 1 circulating in Italy and its connection with northern Africa. Infection, Genetics and Evolution, 28, 144–149. 10.1016/j.meegid.2014.09.014
  10. Lorusso, A., Sghaier, S., Carvelli, A., Di Gennaro, A., Leone, A., Marini, V., Pelini, S., Marcacci, M., Rocchigiani, A. M., Puggioni, G., & Savini, G. (2013a). Bluetongue virus serotypes 1 and 4 in Sardinia during autumn 2012: New incursions or re-infection with old strains? Infection, Genetics and Evolution, 19, 81–87. 10.1016/j.meegid.2013.06.028
  11. Lorusso, A., Sghaier, S., Carvelli, A., Di Gennaro, A., Leone, A., Marini, V., Pelini, S., Marcacci, M., Rocchigiani, A. M., Puggioni, G., & Savini, G. (2013b). Bluetongue virus serotypes 1 and 4 in Sardinia during autumn 2012: new incursions or re-infection with old strains? Infection, Genetics and Evolution: Journal of Molecular Epidemiology and Evolutionary Genetics in Infectious Diseases, 19, 81–87. 10.1016/j.meegid.2013.06.028
  12. Maclachlan, N. J., Mayo, C. E., Daniels, P. W., Savini, G., Zientara, S., & Gibbs, E. P. J. (2015). Bluetongue: -EN- -FR- Fièvre catarrhale ovine -ES- Lengua azul. Revue Scientifique Et Technique De l'OIE, 34(2), 329–340. 10.20506/rst.34.2.2360
  13. Mellor, P. S. (2004). Infection of the vectors and bluetongue epidemiology in Europe. Veterinaria Italiana, 40(3), 167–174. https://pubmed.ncbi.nlm.nih.gov/20419656/
  14. Miranda, M. A., Stegeman, J. A., Bicout, D., Botner, A., Butterworth, A., Calistri, P., Depner, K., Edwards, S., Garin-Bastuji, B., Good, M., Schmidt, C. G., Michel, V., More, S., Raj, M., Søren, S., Nielsen, L., Sihvonen, H., Spoolder, H. H., Thulke, A., . . . Carnesecchi, E. (2017). Bluetongue: control, surveillance and safe movement of animals. EFSA Journal, 15(3)10.2903/j.efsa.2017.4698
  15. More, S., Bicout, D., Bøtner, A., Butterworth, A., Depner, K., Edwards, S., Garin‐bastuji, B., Good, M., Gortázar Schmidt, C., Michel, V., Miranda, M. A., Nielsen, S. S., Raj, M., Sihvonen, L., Spoolder, H., Stegeman, J. A., Thulke, H., Velarde, A., Willeberg, P., . . . Calistri, P. (2017). Assessment of listing and categorisation of animal diseases within the framework of the Animal Health Law (Regulation (EU) No 2016/429): bluetongue. EFSA Journal, 15(8)10.2903/j.efsa.2017.4957
  16. Nicolas, G., Tisseuil, C., Conte, A., Allepuz, A., Pioz, M., Lancelot, R., & Gilbert, M. (2018). Environmental heterogeneity and variations in the velocity of bluetongue virus spread in six European epidemics. Preventive Veterinary Medicine, 149, 1–9. 10.1016/j.prevetmed.2017.11.005
  17. Niedbalski, W. (2015). Bluetongue in Europe and the role of wildlife in the epidemiology of disease. Polish Journal of Veterinary Sciences; 2015; no 2, https://journals.pan.pl/dlibra/publication/114345/edition/99398
  18. Niedbalski, W. (2022). Bluetongue virus in Europe: the current epidemiological situation. Medycyna Weterynaryjna, 78(02), 6619–2022. 10.21521/mw.6619
  19. Regolamento - 1266/2007, https://eur-lex.europa.eu/legal-content/IT/ALL/?uri=celex:32007R1266
  20. Regolamento di esecuzione - 2020/2002, Regolamento di EsecuzioneU.S.C. (2020). https://eur-lex.europa.eu/legal-content/IT/TXT/?uri=celex%3A32020R2002
  21. Regolamento di esecuzione - 2021/620, https://eur-lex.europa.eu/legal-content/IT/TXT/?uri=CELEX:32021R0620&print=true
  22. Regolamento di esecuzione (UE) 2018/1882 della Commissione, Regolamento di EsecuzioneU.S.C. (2018). https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX%3A02018R1882-20240201
  23. Ries, C., Sharav, T., Tseren-Ochir, E., Beer, M., & Hoffmann, B. (2020). Putative Nove lSerotypes ‘33’ and ‘35’ in Clinically Healthy Small Ruminants in Mongolia Expand the Group of Atypical BTV. Viruses, 13(1), 42. 10.3390/v13010042
  24. Ries, C., Vögtlin, A., Hüssy, D., Jandt, T., Gobet, H., Hilbe, M., Burgener, C., Schweizer, L., Häfliger-Speiser, S., Beer, M., & Hoffmann, B. (2021). Putative Novel Atypical BTV Serotype ‘36’ Identified in Small Ruminants in Switzerland. Viruses, 13(5), 721. 10.3390/v13050721
  25. Romero-Trancón, D., Valero-Lorenzo, M., Ruano, M. J., Fernández-Pacheco, P., García-Villacieros, E., Tena-Tomás, C., López-Herranz, A., Morales, J., Martí, B., Jiménez-Clavero, M. Á, Cáceres-Garrido, G., Agüero, M., & Villalba, R. (2025). Emerging Bluetongue Virus Serotype 4 in the Balearic Islands, Spain (2021): Outbreak Investigations and Experimental Infection in Sheep. Microorganisms, 13(2), 411. 10.3390/microorganisms13020411
  26. Sailleau, C., Viarouge, C., Bréard, E., Perrin, J. B., Doceul, V., Vitour, D., & Zientara, S. (2015). Emergence of Bluetongue Virus Serotype 1 in French Corsica Island in September 2013. Transboundary and Emerging Diseases, 62(5), 89. 10.1111/tbed.12207
  27. The Pirbright Institute. (2015, -09-28). Bluetongue virus | Virus | The Pirbright Institute. Retrieved Feb 10, 2025, from https://www.pirbright.ac.uk/our-science/viruses/bluetongue-virus
  28. WAHIS. WAHIS, Italy - Bluetongue virus (Inf. with) - Follow up report 13 [FINAL]. WAHIS. Retrieved May 2, 2025, from https://wahis.woah.org/#/in-review/5507
  29. WOAH. (a). Bluetongue. Retrieved Feb 10, 2025, from https://www.woah.org/en/disease/bluetongue/
  30. WOAH. (b). Bluetongue in Europe: How climate change is shifting disease patterns. Retrieved Jan 20, 2025, from https://www.woah.org/en/article/bluetongue-in-europe-how-climate-change-is-shifting-disease-patterns/

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