Epizootic haemorrhagic disease
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.
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.
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.
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.
Last updated: 12.06.2023