Epizootic Hemorrhagic Disease (EHD) is a viral infection of domestic and wild ruminants. White tailed deer and other free-ranging ruminants are most affected. EHD is a notifiable disease. It has the same host spectrum as bluetongue, and clinical symptoms are similar. Among domestic ruminants, cattle are most affected by EHD. Morbidity can be as high as 20%, but mortality is usually low. Still, EHD infection of cattle can cause tremendous production losses, especially in dairies.
Passive surveillance for EHD is hindered by the similarity of its symptoms to bluetongue disease. Active monitoring of disease incidence is currently not feasible, because there are no commercially available serological assays.
EHD virus (EHDV) is closely related to bluetongue virus (BTV) and belongs to the same taxonomical genus (Orbivirus; family Reoviridae). They can be differentiated on the genetic level by RT-PCR and sequencing. Serological differentiation by monoclonal antibodies is also possible. There are 8 recognized serotypes of EHDV which can be differentiated by neutralization assays. Like BTV, EHDV is spread by Culicoides insects.