Research and analysis

28 November 2023: epizootic haemorrhagic disease in Europe

Updated 28 August 2024

Updated Outbreak Assessment 5.

Disease report

Following initial confirmation of epizootic haemorrhagic disease (EHD) in France on 21 September 2023, 3,527 outbreaks have been recorded on farms in southern France, primarily in Pyrénées-Atlantiques, Hautes-Pyrénées and nearby municipalities (MASA 2023) (Figure 1). Since our previous report on 26 October 2023, there have also been additional outbreaks of EHD in Spain and Italy, with the Spanish Ministry of Agriculture, Fisheries and Food reporting outbreaks in a further 7 regions and one report of epizootic haemorrhagic disease virus (EHDV) in one wild fallow deer in Sardinia, Italy (World Organisation for Animal Health (WOAH)).

Figure 1: Map showing municipalities in southern France positive for EHDV (solid orange) and the 150km restriction zones (orange lines), as reported by the French Ministry of Agriculture and Food Sovereignty as of 23 November 2023 (Source: MASA press release on 20/11/2023, accessed 24 November 2023).

Figure 2: Map showing epizootic haemorrhagic disease outbreaks detected since 25 October 2022 (orange dots) and outbreaks that have occurred between 29 October 2023 and 26 November 2023 (red dots) in Europe reported by ADIS (Source: Bulletins hebdomadaires de veille sanitaire internationale du 28/11/2023 (plateforme-esa.fr) accessed 28 November 2023). EHDV outbreaks in wild deer are also shown (green triangles).

Situation assessment

The EHD virus (EHDV) is notifiable in the UK and under EU Animal Health Law and has been a listed disease by WOAH since 2008. The virus infects many ruminant species and may manifest as haemorrhagic disease, although sub-clinical infection may also occur (WOAH, 2019). EHDV is present in neighbouring countries to Europe, across the Middle East and North Africa. To date, there are 8 recognised serotypes of epizootic haemorrhagic disease virus (EHDV), though it is likely that more exist (Pirbright, 2022). EHDV-8 is the serotype previously reported in Italy, Spain and Portugal.

France

As of 24 November, 3,527 outbreaks of EHDV have been identified on farms in France. The municipalities affected and 150km regulated zones are illustrated in Figure 1. Since our last report, outbreaks have been identified in the newly affected departments of Deux-Sèvres, Lot-et-Garonne, Lot, Corrèze, Gironde, Dordogne, Vendée and Loire- Atlantique. The first case in wildlife was reported on 25 September 2023 in a red deer found dead near a premises with confirmed EHDV in cattle. (BHVSI-SA, 2023).

It has been suggested that the primary vectors (Culicoides) are capable of travelling up to 150km across land in one day in favourable wind conditions (Mellor 2002). However, at this time there is no clear indication as to how EHD or infected Culicoides crossed the Pyrénées mountains. To control the spread of EHD, French authorities have prohibited the export of live cattle from all affected regions. The additional outbreaks since our last report have increased the restriction zone further North, including several new departments.

Spain

The Spanish Ministry of Agriculture, Fisheries and Food have documented the spread of EHDV across mainland Spain (Figure 2). There is continued detection of outbreaks throughout the country, in already infected regions (ESA 2023).

The total number of outbreaks in Spain reported by ADIS this year is 250 from 1 January 2023 to 17 November 2023 (ADIS, 2023). This means that there has been a 100% increase in outbreaks since 26 October. Current measures in Spain involve disinfection of animals and farms in affected areas and the monitoring of sheep and goat farms in affected zones, as these may be carriers of EHDV without showing clinical symptoms (PAFF 2023). All mainland provinces of Spain are currently under restriction (Update on the situation of Epizootic Haemorrhagic Disease).

Since our last update on 26 October 2023, 125 outbreaks have been reported, according to ADIS summaries. Between 15 November and 22 November 2023, 7 new regions in Spain have confirmed cases of EHD, along with reports in already affected regions. All but one of these were detected in cattle farms in the regions of Medina de Pomar and Villadiegos (Burgos); Riaño (León); Piloña (Asturias); Cerdanya (Puigcerdá) (Girona); and Quinto (Zaragoza). One case has also been detected in deer in the region of La Ribera Alta-Alzira (Valencia).

Culicoides obsoletus has been implicated as a potential significant vector in the spread of EHD in Spain (PAFF 2023). This recent surge in outbreaks in Spain could be associated with Culicoides populations peaking, which occurs around mid-summer to late autumn  (Rocklöv et al., 2020).

Figure 3: Map showing epizootic haemorrhagic disease outbreaks detected in 2022 (orange dots) and outbreaks that have occurred in 2023 (blue dots) in Spain reported by the Spanish Ministry of Agriculture, Fisheries and Food. (Source: Documento (mapa.gob.es), accessed 24 November 2023).

Portugal

Since our last report, no further outbreaks of EHD have been reported in Portugal, meaning the total remains at 73 outbreaks. (ADIS. 2023).

Italy

Since our last report, Italy made a notification to WOAH of a report of EHD in wild fallow deer. This was in Pula, Sardinia, and involved one deer. (See figure 2 for map.)

Conclusion

EHD continues to be detected in France, Spain and Italy. With France and Spain reporting a significant increase in outbreaks on cattle farms, this has caused an expansion of the restriction zone further North to include more Northern departments of France and the whole of Spain being under movement restrictions.

Currently, the outbreaks in France are located in areas of medium to very high abundance of C. obsoletus and C. scoticus, and the climate of the Pyrénées-Atlantiques region has particularly mild winters resulting in reduced periods of ‘vector inactivity’ (Anses Weekly Bulletin of International Health Surveillance in Animal Health (BHVSI-SA) for 21 September 2023). This could explain the large number of outbreaks in recent weeks, and there could be more cases of EHD reported in the region. However, a drop in temperature throughout the winter months may also impact the disease dynamics.

Culicoides population peaks mid to late summer, and during early Autumn the conditions are optimal for EHD transmission by infected midges (Plateforme 2023) (Wittman et al., 2002). As we approach the end of Autumn and temperatures are dropping, we expect to see a decrease in Culicoides populations. Furthermore, EHD requires a minimum average temperature of 19.5°C for replication and for the extrinsic incubation period (EIP) of the virus to complete (Wittmann et al., 2002). A decrease in the temperature throughout winter may contribute to a decrease in the number of outbreaks that occur in western Europe. Although this is unpredictable as Spain reported a low number of outbreaks in 2022 (2). However, Culicoides where EIP was successful prior to changes in temperature can continue to infect livestock throughout their life span (Brand et al., 2017). Typically, they live 2 to 3 weeks, but some have been documented to survive for longer (3.5 months) in favourable conditions (Mellor et al. 2000) For this reason, there may be a delay before we see a decrease in number of outbreaks even with the temperature drop in winter.

Culicoides species are potentially capable of travelling up to 150km over land and 700km over water in one day (Mellor et al., 2000). It should be noted that the outbreaks that occurred in French cattle farms are close to recent outbreaks that occurred in Spain. The route of entry into France remains unclear. Seasonal changes may reduce vector activity throughout the coming colder months. If spread continues and outbreaks occur within 50km from the coast this would be of importance to Great Britain as there is a greater potential for windborne incursion from the coast. It should also be noted that Loire-Atlantique is close to the Brittany region of France which has a very high livestock density.

Trade of live ruminants and germinal products from France, Portugal, Spain and Italy has been postponed as they are no longer able to comply with relevant animal health certificates.

The possibility for the windborne incursion of midges to Great Britain from the near continent is monitored frequently, with a collaborative effort between APHA, The Pirbright institute (as vector and disease experts) and the Met Office (who can predict potential airborne movement of vectors into Great Britain). Currently, the trade of live animals from the affected areas is impacted due to the inability to comply with health certificate attestations required for import.

Therefore, we consider the risk of introduction of EHDV into Great Britain via movement of live animals and or vectors remains at very low. We will continue to monitor the situation.

Authors

Megan Arter-Hazard

Adem Yusuf

Dr Sonny Bacigalupo

Anthony Pacey

Dr Lauren Perrin

References

ADIS (2023) Animal Disease Information System (ADIS) (europa.eu), Report document 01/01/2023-17/11/2023 Accessed 24 November 2023

BHVSI-SA. 2023. Weekly Bulletin of International Animal Health Surveillance (BHVSI-SA) [Online]. Available: Bulletins hebdomadaires de veille sanitaire internationale du 21/11/2023 (plateforme-esa.fr) Accessed 24 November 2023

Ministerio de Agricultura, Pesca Y Alimentación (2023a).Actualización Situación de Enfermedad Hemorrágica Epizoótica (22/11/2023) Documento (mapa.gob.es) Accessed 24 November 2023

Epizootic Haemorraghic Disease- France Ministry of Argiculture Accessed 24 November 2023

EFSA (2009) Scientific Opinion on Epizootic Haemorrhagic Disease - - 2009 - EFSA Journal - Wiley Online Library

McGregor et al. (2019) Vector Competence of Culicoides sonorensis (Diptera: Ceratopogonidae) for Epizootic Hemorrhagic Disease Virus Serotype 2 Strains from Canada and Florida - PMC (nih.gov)

Mellor, P. S., J. Boorman, and M. Baylis. “Culicoides biting midges: their role as arbovirus vectors.” Annual review of entomology 45, no. 1 (2000): 307-340.

Ministerio de Agricultura, Pesca Y Alimentación (2023b). Maladie hémorragique épizootique (MHE) : point de situation sur une maladie émergente [Online]. Accessed 18 October 2023

PAFF Animal Health and Welfare committee meetings (2023) Update on Epizootic Haemorrhagic Disease (EHD) epidemiological situation in Spain 13 July 2023. Situación actual de la pandemia de IA (europa.eu) Accessed 18 October 2023

ProMed (2022) Promed Post - ProMED-mail (promedmail.org)

Rocklöv, et al. (2020). Climate change: an enduring challenge for vector-borne disease prevention and control

Wittmann (2002) Effect of temperature on the transmission of orbiviruses by the biting midge, Culicoides sonorensis - Wittmann - 2002 - Medical and Veterinary Entomology - Wiley Online Library

WOAH (2019) AETIOLOGY (woah.org)

Any enquiries regarding this publication should be sent to us at iadm@apha.gov.uk