The disease is endemic in areas of the Americas, Africa, Eastern Europe, Australia, and Asia where the biological vectors are active throughout the year. It is an OIE list A disease. The specific suggestions mentioned in this paper only cover BTV and EHDV infections. Other arthropod borne virus infections of ruminants, such as for instance, Rift Valley Fever, should be considered separately. The severity of clinical signs depends on the virus strain and the species and breed of animal affected.
Clinical signs can be very variable, ranging from mild to severe and death.
The severity of clinical signs depends on the virus strain as well as the species and breed of animal affected. The clinical signs are described in the OIE Manual of Standards for Diagnostic Tests and Vaccines. The effects on animal welfare vary with the severity of the disease. Subclinical infections are very common in all ruminant species in infected areas. Transmission takes place via certain species of Culicoides biting midges which are biological vectors.