BVD virus belongs to Flaviviridae
and Pestivirus. It is a single-stranded RNA, enveloped virus. The fresh diseased material was negatively stained by ultra-thin sectioning, and observed under an electron microscope that the virus particles were spherical and had a diameter of about 24-30 nm.
The virus is sensitive to organic solvents such as ether and chloroform, and can be inactivated. The virus suspension is significantly weakened after pancreatin treatment (0.5 mg / ml, 60 minutes at 37 °C), and the virus is relatively weak at pH 5.7-9.3. Stable, beyond this range, the viral infectivity decreases rapidly.
The source of infection is mainly sick animals. Diseased cattle's secretions, excreta, blood and spleen all contain the virus and are transmitted by direct or indirect contact.
Irregular rotten spots and ulcers appear mainly in the digestive tract and lymph tissues, the oral cavity (oral mucosa, gums, tongue and hard palate), pharynx, and nasal mirror. The esophageal mucosa is the most characteristic of rotten spots. There are bleeding spots and ulcers in the mouth, esophagus, true stomach and trachea of aborted fetuses. Dysfunctional calves can severely see cerebellar hypoplasia and hydrocephalus on both sides of the ventricle.
The main symptoms of the disease are fever, diarrhea, cough, and mucosal ulcers, which often cause cows' milk production to decrease, beef cattle's meat production rate to decrease, but also cause pregnancy cows to have abortions and give birth to stillbirths and malformations A disease that can cause serious harm to the cattle industry.