It is an acute contact infectious disease of pigs, also known as swine cholera. It was first discovered in the United States in 1885 and later spread to all continents. This has happened in most provinces in China. In 1903, American veterinarian Deshine and Dorset identified that the cause of the disease was classical swine fever virus in the genus Pestivirus of the Chronoviridae family. It develops mainly through direct contact, or as a result of exposure to contaminated media. The digestive tract, nasal mucosa, and ruptured skin are all routes of infection. It can occur all year round, mostly in spring, summer and rainy seasons.
Swine fever symptoms
Swine fever can cause sick pigs to have a depressed mood, drooping heads and tails, arched back, sleepy, sleep in a pile, or drill a nest of grass. It is not sensitive to external stimuli. Left and right, persistence, weakness in walking limbs, slow movement, unstable swing, constipation first, diarrhea later. There are purplish-red bleeding points that do not fade with finger pressure at the base of the ears, abdomen, and inside the extremities. Sow is infected for a long time after infection, and has a low conception rate, miscarriage, stillbirth, mummy or abnormal fetus. The piglets born are infected and die or become stiff. Most pigs die 5 to 15 days after infection, and the piglet mortality rate can reach 100%.
Types of swine fever
The incubation period of classical swine fever is generally 5-7 days. According to clinical symptoms, it can be divided into four types: the most acute, acute, chronic and mild type.
How is swine fever spread?
The disease only infects pigs under natural conditions. Pigs and wild boars of different ages, sexes, breeds are susceptible and can occur throughout the year. Sick pigs are the main source of infection. Sick pigs' excreta and secretions, dead pigs and organs and corpses, blood, meat, offal, waste water, waste contaminated feed, and pigs can be spread by drinking water. Transmission is mainly through contact, through a digestive tract infection. In addition, sows infected with diseased and attenuated strains can also vertically infect fetuses through the placenta, producing weak piglets, stillbirths, and mummy fetuses.
Swine fever diagnosis
Clinical diagnosis is in large-scale pig farms. For example, several or more sick pigs in the herd have high fever, depressed spirit, decreased appetite, general weakness, weak hindquarters, dry stool, and thinning at the later stage. Yellow, green, and sometimes bloody, thin skin with bleeding spots, purple ears, high mortality, can be initially judged to be suspected of swine fever. Detection of serum antibodies Detection of serum antibodies can provide a basis for swine fever immunity, in particular, enzyme-linked immunosorbent assays are important for detecting atypical swine fever and mild swine fever.
Swine fever virus
Classical swine fever virus can be cultured in pig embryo or suckling pig spleen, kidney, bone marrow, lymph nodes, white blood cells, connective tissue or lung tissue cells, but no obvious lesions are produced on these cells. The chicken Newcastle disease virus enhanced test (END test) can be used to determine swine fever virus as a method for diagnosing swine fever.
Swine fever virus signature
Classical swine fever virus is an ssRNA virus, which belongs to the genus Flaviviridae. Its RNA is a single positive strand. The virus particles are round, with a size of 38 to 44 nm. The nucleocapsid is a stereosymmetric icosahedron. The floating density of cesium chloride is 1.15 to 1.17 g / ml, and the envelope is enveloped. Classical swine fever virus replicates in the cytoplasm, does not agglutinate red blood cells, and has antigens associated with bovine diarrhea virus. The virus is sensitive to ether and resistant to temperature, ultraviolet rays, and chemical disinfectants.
Swine fever treatment
Swine fever prevention
Prevention: A. Immunization. B. Carrying out immune monitoring, using enzyme-linked immunosorbent assay or forward indirect hemagglutination test and other methods for immune antibody monitoring. C. Eliminate recessive infected pigs in a timely manner. D. Adhere to the breeding management system of self-reproduction and self-support, all-in and all-out. E. Do a good job of isolation, sanitation, disinfection and pest control of pig farms and pig houses to reduce the invasion of swine fever virus.
Vaccine for swine fever
Classical swine fever is a highly infectious disease that often causes devastating losses to the pig industry. The most effective way to prevent swine fever is to get a swine fever vaccine. In order to enable the majority of pig farmers to correctly select and effectively use the swine fever vaccine, the types and use methods of the swine fever vaccine are described here: There are three main types of vaccines:
1. Live swine fever vaccine (I) --- suckling rabbit seedlings.
2. Live swine fever vaccine (II) --- cell vaccine.
3. Live swine fever vaccine (I)---spleen vaccine.