How is the Swine fever caused? What is the pathogenesis?Swine fever is caused by swine fever virus (HCV). The swine fever virus belongs to the family Flaviviridae. It has common antigenicity with bovine mucosal disease virus and equine arteritis virus. Pigs are the only natural host of the swine fever virus, and various pigs are susceptible to swine fever virus. Swine fever is a global epidemic. The characteristics of swine fever are acute onset, high heat retention and small blood vessel degeneration, causing generalized small spot bleeding and spleen infarction. Chronic disease manifests as fibrinous necrotic enteritis.
The symptoms of swine fever can be divided into three categories, namely acute type, acute type, and late type. Acute swine fever is caused by HCV virulentness. At the beginning, only a few of the pigs showed clinical symptoms, and the performance was sluggish. When they were driven away, they stood aside, showing an arched back or cold, or bowing their tails. At the same time, the appetite is reduced and the food is stopped. The body temperature of the sick pigs rises to 41℃ up and down, and the high can reach above 42℃. When the body temperature rises, the number of white blood cells decreases, about 9000/mm3, or even as low as 3000/mm3. The course of chronic swine fever can be divided into three phases. In the early stage, the acute phase, there are symptoms such as loss of appetite, mental dysfunction, elevated body temperature and leukopenia. After a few weeks, the appetite and general condition are significantly improved, the body temperature drops to normal or slightly higher than normal, but there is still a decrease in white blood cells. For the second period. In the later stage, the sick pigs reappeared with loss of appetite and mental wilting, and the body temperature rose again until it fell shortly before dying. Sick pigs grow slowly and often have skin damage. Chronic swine fever pigs can survive for more than 100 days. Delayed swine fever is the result of congenital HCV infection. Embryonic infection with low-toxic HCV, such as the birth of normal piglets, has a high level of viremia for life, and can not produce neutralizing antibodies to HCV, which is a typical immune tolerance phenomenon. Infected pigs can be normal for several months after birth, followed by mild loss of appetite, depression, conjunctivitis, dermatitis, diarrhea, and movement disorders. Sick pigs have normal body temperature, most of them can survive for more than 6 months, but eventually die, and congenital HCV infection in pregnant pigs can lead to miscarriage, fetal mummies, malformations, stillbirth, weak babies with trembling symptoms or healthy infections. Piglets. Piglets with intrauterine infections have common bleeding and high birth mortality.
Since swine fever is a viral disease, there are no effective therapeutic drugs and treatment methods. In recent years, experiments have been conducted on the prevention and treatment of swine fever with interferon and Chinese herbal preparations, but they have not been successful. Antibiotics and sulfonamides are basically ineffective. At present, the only effective therapeutic preparation is swine fever high serum, but it is also limited to the pigs in the early stage of the disease, and the pigs in the middle and late stages of the disease are basically ineffective. Moreover, the manufacturing process of the piglet high serum-free serum is long, time-consuming and labor-intensive, and the cost is high, and it cannot be mass-produced, and the fundamental problem of piglet prevention and control cannot be solved.
Swine fever prevention. The pigs are given a swine fever vaccine, and the first time is 25 to 30 days old. The second immunization can be carried out with swine fever, erysipelas biloba or triple vaccine, and the time is carried out at 2 months of age (when transferred). If it is necessary to purchase pig breeds from other places, they must be kept in isolation for about half a month after shipment and vaccinated before they can be mixed. Do a good job in veterinary hygiene and disinfection of housing, environment and related tools.