Epizootic haemorrhagic disease (EHD) is a viral disease of wild and domesticated ruminants. It can cause high rates of disease and death in certain deer species. Humans are not affected by the disease.

North and South America, Asia, Africa, Europe (including countries bordering the Mediterranean Sea such as Israel, Turkey, Jordan, Morocco, Algeria, Tunisia, Italy, Spain) and Australia

Wild and domesticated ruminants. Classically, the disease affects white-tailed deer in North America. Cattle may also become clinically ill, whereas disease of small ruminants (e.g. sheep, goats) does not occur.

Transmission of the EHD virus (EHDV) occurs via the bite/bite of insects (gnats). Unborn fetuses can become infected in the womb. There is no transmission between born animals in the absence of the midges, so EHD is not a contagious disease. In temperate zones, infection usually occurs in late summer/fall, while in tropical zones it can occur year-round.

5-10 days (deer)

Clinical disease mainly affects certain deer species, but may also occur in cattle, although most infections in cattle do not result in disease (subclinical course). Fever, edema, respiratory and swallowing problems, hemorrhage, mucosal and hoof ligament inflammation, lameness, lassitude may occur. Abortions and stillbirths also occur.

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

Vaccines are used sporadically in Japan and the USA. These are live attenuated vaccines or inactivated vaccines.

Epizootic hemorrhagic disease has not been reported in Austria. However, in 2022, evidence of EHDV was reported in Spain and Italy. It is possible that the disease will spread further north in the future as a result of climate change.

Epizootic hemorrhagic disease is caused by an orbivirus (EHDV) related to the bluetongue virus and the African horse sickness virus, which is also transmitted by insects (midges). The disease has not yet been observed in Europe, but is spreading increasingly as a result of climate change.

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.