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. In 2023, the disease also occurred 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 in Japan and the USA. These are live attenuated vaccines or inactivated vaccines. There is currently no vaccine licensed in the EU.

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 divided into 10 different segments. At least eight different serotypes are distinguished. 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 glutaraldehydes, acids, alkalis (2% w/v NaOH), 2-3% w/v sodium hypochlorite, iodophores, and phenols are effective.

Symptomatology

EHD is an important differential diagnosis to bluetongue in deer. In cattle, bluetongue (BT), bovine viral diarrhea (BVD), foot-and-mouth disease (FMD), infectious bovine rhinotracheitis (IBR), vesicular stomatitis (VS), and malignant catarrhal fever (BKF) are 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 is also detectable in EDTA blood for a long time (> 50 days after infection). Antibodies can be detected by competitive ELISA from 10-14 days after infection.

Sample material required: EDTA blood and serum in live animal; spleen, lungs, lymph nodes, liver in dead animal.

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