Читать книгу Farm Animal Medicine and Surgery - Graham R Duncanson - Страница 96

The causative organism, Bluetongue virus (BTV), is an Orbivirus with 24 serotypes, which tend to be restricted to certain areas. Various species of Culicoides midges are required as vectors. Replication of the virus has to occur in the vector. Serotype 8 first came to northern Europe in 2006 and caused the birth of ‘Dummy type’ calves. BTV is primarily a disease of sheep and goats, but the first recorded case in the UK was in a cow. Normally the virus is asymptomatic in cattle except for causing abortions and stillbirths with central nervous system (CNS) defects. If there are signs of clinical disease in cattle they are caused by endothelial damage and disseminated intravascular coagulation (DIC), and are shown as haemorrhage, ischaemia, inflammation and oedema. The lesions are common in areas subject to mechanical trauma and abrasion, e.g. the feet, mouth and eyes. There is fever up to 42°C. The diagnosis is confirmed by PCR for viral RNA. It can detect all 24 serotypes. There is no specific treatment for BTV. Antibiotics and non-steroidal anti-inflammatories (NSAIDs) are helpful. Nursing is vital and should include offering water and mushy food, and providing deep bedding out of the sun and heat. There are vaccines available which are monovalent for each serotype. Cattle require two doses separated by 2 weeks.