Bovine viral diarrhea (bovine viral diamhe, BVD) is a type of bovine viral diamhe virus (bovine viral diamhe virus BVDV) that can infect cattle,goats,sheep,pigs and other livestock animals.It can also cause camels and deer.Such as other wild animal infections, the pathogen is the most common clinically infecting cattle.At present, BVD is still a major economic disease and immunosuppressive disease that endangers the world's cattle industry.The disease can directly lead to poor reproduction and production performance of cattle,and indirectly increase the loss and prevention of cattle respiratory and digestive diseases.BVDV can be permanently transmitted in the herd through persistently infected fetal cattle.Based on the prevalence and harm of BVD in Ningxia, it is an urgent and long-term task to promote the purification of the disease on large-scale dairy farms,which is of great significance to the healthy development of Ningxia's dairy industry.Numerous large-scale dairy farms in Ningxia have eliminated persistently infected cattle through detection and immunization to protect the herd to reduce the emergence of new persistently infected cattle,effectively controlling and purifying the disease.