The Epizootic Haemorrhagic Disease (EHD) and the Bluetongue disease serotype 3 (BTV-3) emerged in September 2022 in the south of Europe and in September 2023 in the Netherlands, respectively. Both diseases are spread by a small midge called Culicoides. Although this insect can be present all year round in some parts of Europe, it is more active from summer to the end of the year. As a result, the number of clinical cases of these two diseases started to increase again in 2024 and the infected areas expanded.
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EHD continues to expand north and east
To date, the epizootic has mainly affected Spain, Portugal, France and Andorra. The Italian islands of Sardinia and Sicily were also affected in 2022 (11 cases in all), but no new cases have been reported since. Overall, 4,667 outbreaks had been reported by the end of May 2024, the vast majority in France (4,310 outbreaks), particularly in the south-west of the country.
As vector activity resumed with the arrival of summer, the geographical range of the disease gradually expanded (towards the north and east of France) and the number of cases began to rise again. In addition, the movement of animals within the area considered to be infected is probably responsible for the appearance of a secondary cluster, which in turn is responsible for the spread of the disease to another front. Within the Iberian Peninsula, new outbreaks have appeared in the northern half. By the end of the summer of 2024, the disease had spread to around the western half of France and the whole of Spain and Portugal.
To date (29 October 2024), around 7,000 outbreaks have been declared, particularly in France (6,789 since the start of the epizootic, including 2,479 since 1 June 2024).
BTV-3 progresses in all directions
Since it first appeared in the Netherlands in September 2023, Bluetongue linked to serotype 3 has spread rapidly to Belgium, western Germany and southern England. With the resumption of seasonal vector activity in the summer of 2024, the disease continued to spread:
- Westwards: several new outbreaks have been detected in England. It would appear that the disease is spreading northwards in this country, although the majority of cases remain close to the North Sea coast.
- To the east, the disease has also spread in Germany, and now covers the whole country. Cases have also been reported in the Czech Republic (1st case on 6 September 2024) and Austria (1st case on 13 September 2024)
- Southwards: unsurprisingly, the first cases were detected in mid-summer in France (30 July 2024) and Luxembourg (2 August 2024). Switzerland, further east, reported its first case on 30 August 2024.
- Northwards: more surprisingly, territories hitherto less favourable to the activity of Culicoides vectors of the disease also reported their first cases during the summer: Denmark (8 August 2024), Norway (21 August 2024, on the southern coast), Sweden (4 September 2024, on the south-west coast, close to Denmark and Norway).
Around thirty outbreaks have also been reported in Portugal and southern Spain since 13 September 2024. Genetic analyses have shown that the virus strain has a high degree of homology with the strain of Dutch origin, but to date the appearance of new outbreaks several hundred kilometres away from the most southerly cases identified has not been explained. Ten outbreaks have also been identified in eastern Greece. The results of genetic analyses of the strains are not available, but it cannot be ruled out that the strain originated in the Near East rather than Western Europe.
The spread of the disease also resumed in Sardinia, with 7 outbreaks reported in July, 396 in August, 1,062 in September and 280 in October. However, to date, this strain, which has been present on the island for several years and is different from the one that appeared in the Netherlands in 2023, does not appear to have spread beyond this Italian island.
The number of cases reported by country since the start of the epizootic is shown in table 1. (Bulletin hebdomadaire de veille sanitaire internationale du 22/10/2024)
| Country | Number of outbreaks* |
| Austria | 8 |
| Belgium | 3,668 |
| Czech Republic | 25 |
| Denmark | 791 |
| France | 6,595 |
| Germany | 13,180 |
| Greece | 10 |
| Italy (Sardinia) | 1,765 |
| Luxembourg | 2 |
| Netherlands | 7,604 |
| Norway | 78 |
| Portugal | 3 |
| Spain | Approx. 30 |
| Sweden | 3 |
| Switzerland | 1,352 |
| United Kingdom | 143 |
France is the first country to be co-infected with EHD and BTV
EHD arrived in France in September 2023 in the south-west, close to the Spanish border, and progressed towards the north and east of the country. BTV-3 arrived in the north (close to the Belgian border) and progressed rapidly towards the south and east. Although, to our knowledge, no herds co-infected with the two viruses have been reported, the two epizootics have co-existed in several French departments since the beginning of September 2024. It is possible that this zone of co-infection will spread across France in the coming weeks and reach neighbouring countries. However, mass vaccination of animals against these two viruses could slow the spread of the two diseases.
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BTV-12: a new threat ?
A new BTV serotype, BTV-12, was isolated in the Netherlands in early October from two farms around ten kilometres apart. The first case involved sheep and the second cattle. This was the first description of this serotype in Europe. Since then, 6 other outbreaks have been reported. To date (29 October 2024), there is no epidemiological evidence to establish the origin of this new serotype. However, the strain appears to be genetically distant from strains known from Africa, Israel, Asia and the Americas. It is also too early to predict the geographical spread of this virus.
Key messages
- To date, EHD is present in 3 countries (Spain, Portugal and France) as well as in Sicily and Sardinia. Around 7,000 outbreaks have been recorded since the epizootic began in September 2022.
- BTV-3 is present in 15 countries, mainly in western Europe, but it is spreading rapidly, particularly eastwards. To date, more than 35,000 outbreaks have been recorded since the disease emerged in September 2023.
- The two epizootics met geographically in France in September 2024.
References
https://ruminants.ceva.pro/epizootic-haemorrhagic-disease-bluetongue
https://www.plateforme-esa.fr/fr/bulletins-hebdomadaires-de-veille-sanitaire-internationale-
https://www.fli.de/en/news/animal-disease-situation/bluetongue-disease/
https://ruminanthw.org.uk/latest-bluetongue-announcement/
https://www.vettimes.co.uk/news/new-bluetongue-warning-as-denmark-confirms-infections/
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