Epizootic haemorrhagic disease (EHD) is a viral disease of wild and domesticated ruminants and camelids. High rates of disease and death can occur in certain deer species. The trigger is a virus related to the bluetongue virus (EHDV), which is also transmitted by insects (gnats). EHD has also been occurring in Europe since 2022. This year, cases were reported from Italy (Sardinia, Sicily) and the south of Spain. since 2023, the disease also occurres in Portugal, northern Spain and France. Humans are not affected by the disease.

worldwide

Most wild and domesticated ruminant species as well as camelids are susceptible to infection with EHDV. Classically, the disease affects white-tailed deer in North America. Cattle can also become clinically ill, whereas disease in small ruminants (e.g. sheep, goats) or camelids does not usually occur. Before its first appearance in Europe, EHD had already been described in North and South America, Asia and Africa (including countries bordering the Mediterranean such as Israel, Turkey, Jordan, Morocco, Algeria and Tunisia), as well as Australia.

Transmission takes place via the sting/bite of insects (gnats; Culicoides sp.), so it is not a contagious disease. Unborn calves can be infected in the womb in the same way as bluetongue. In temperate zones, infection usually occurs in late summer/autumn, whereas in tropical zones it can occur all year round.

2-10 days (deer)

Clinical disease mainly affects certain deer species, but can also occur in cattle. Fever, oedema, respiratory and swallowing problems, haemorrhage, inflammation of mucous membranes and hoof ligaments, lameness, lassitude and inappetence may occur. Abortions and stillbirths also occur. Peracute, acute and chronic forms occur.

A specific therapy is not possible. Diseased animals can only be treated symptomatically.

Vaccines are occasionally used. These are live attenuated vaccines (not authorised in the EU) or inactivated vaccines. An inactivated vaccine against EHDV serotype 8 is authorised in the EU. In France, the targeted use of this vaccine is also intended to prevent the spread of EHD to the north-east.

EHD has not yet occurred in Austria. We have established procedures for the virological and serological diagnosis of the disease, with which suspected cases can be clarified quickly.

EHDV are non-enveloped viruses with double-stranded RNA, which are divided into 10 different segments. Seven different serotypes are currently differentiated (previously eight, whereby the previously differentiated EHDV-1 and EHDV-3 are now regarded as a single serotype). The cases in Europe are assigned to the EHDV-8 serotype. EHDV is unstable at higher temperatures (inactivation at 50 °C and 3 h exposure time; or 60 - 121 °C and 15 min exposure time). Organic solvents such as ether and chloroform are relatively ineffective (unenveloped virus). Disinfectants based on ß-propiolactones, 2% w/v glutaraldehyde, acids, alkalis (2% w/v NaOH), 2-3% w/v sodium hypochlorite, iodophores and phenols are effective.

Symptoms

EHD is an important differential diagnosis to bluetongue in deer. In cattle, bluetongue (BT), bovine viral diarrhoea (BVD), foot-and-mouth disease (FMD), infectious bovine rhinotracheitis (IBR), vesicular stomatitis (VS) and malignant catarrhal fever (BKF) can be considered as differential diagnoses. Sheep and goats do not become clinically ill.

Due to the non-specific symptoms, a laboratory diagnostic clarification is essential. The virus itself can be detected very sensitively and specifically in real-time PCR. Similar to BTV, EHDV can also be detected in EDTA blood for a long time (> 50 days after infection). Antibodies can be detected in competitive ELISA from 10-14 days after infection.

Sample material required: EDTA blood and serum from live animals; organ material such as spleen, lungs, lymph nodes or liver from dead animals.

In all cases, samples should ideally be sent to the laboratory with the addition of refrigerants and in compliance with the relevant transport regulations (UN3373) by an authorised logistics company.