A severe viral disease caused by an orbivirus transmitted mainly by gnats of the genus Culicoides. Transmission sexually and across the placenta can also occur. Because the vector is a gnat, the spread of this disease occurs primarily in the late summer and fall. The virus is endemic in many areas and cattle and wild ruminants, or white-tailed deer, act as reservoirs. Goats are commonly infected with the virus but rarely show any signs of clinical disease; it is a self-limiting disease in goats.
Symptoms: Affects sheep of all ages; goats rarely show clinical disease. Clinical signs range from transient fever and swelling of the face, muzzle, and ears; large amount of nasal discharge which may cause crusting around the nose; oral mucus membranes become dark pink and as the disease progresses, small hemorrhages and ulcers may form on the roof and corners of the mouth. The tongue may become cyanotic (blue) but not as common as the name indicates. Laminitis can develop caused by inflammation of the coronary band and tissues of the foot to the point that some animals may slough their hooves. Diarrhea and wool-break will also occur in infected animals. Bluetongue virus will cause abortions, stillbirths and weak lambs.
Diagnosis: By the presence of clinical signs similar to those reported in sheep have been documented in goats.
Treatment: Minimize animal stress and antibiotic treatment for secondary infections.
Prevention: Controlling breeding areas for biting gnats. Keeping animals away from areas where biting gnats are present. Vaccine is available for sheep.