In recent years, there have been more and more vaccines in pig farms, but the prevention and control of the disease is still unsatisfactory. The majority of the farm diseases still occur from time to time. This is caused by failure of the farm's immune system. There are many reasons for immune failure. , I think there are mainly the following aspects:
Immunosuppression leads to immune failure
Immune failure caused by immunosuppressive diseases,
Such as porcine reproductive disorder and respiratory syndrome virus, porcine circovirus type 2, swine fever virus, Actinobacillus pleuropneumoniae, Eperythrozoon, etc. will invade the body's immune system, destroy immune cells, so that the body can not produce adequate protection , thereby affecting the vaccine's immune effect.
Abuse of immunosuppressive drugs, such as certain chloramphenicol, kanamycin, glucocorticoids, tetracycline, florfenicol, sulfonamides, antiviral chemicals, etc., can reduce the body's leukocyte, obstruct the antigen, and respond insufficient. Some have a certain inhibitory effect on the proliferation of body B lymphocyte cells and can significantly affect the immune effects of bacterial and viral vaccines. In particular, the use of these drugs in an irregular manner before and after immunization results in a reduction of the body's leukocytes, thereby affecting the immune response and resulting in immune failure.
Moldy and degenerative feeds are used. Moldy feed contains various mycotoxins that can damage immune organs, resulting in lymph node bleeding and edema. Lack of nutrition, poor health, and adverse stress all affect the immune response.
Some problems with immunization result in immune failure
Effects of maternal antibodies, maternal antibodies are uneven at the time of first exemption, when maternal antibody levels are high, immunity due to antigens in the vaccine is neutralized by maternal antibodies, or maternal antibodies are too low and delayed No immunization occurs and a blank period of immunization occurs. During this period, it is easy to cause immunological failure if wild-type virus is infected.
The period of protection of the vaccine is too short. Some vaccines have a short protection period. When the antibody level is reduced to provide no effective protection, the immune failure is easily caused. Although the original vaccine is immune, it still has a pig disease.
Interfering between vaccines, when two or more non-cross-reactive antigens are simultaneously inoculated, the body's antibody response to one of the antigens is significantly reduced, thereby affecting the immune effect of these vaccines.
When vaccines are not properly selected, selecting different serotypes or variant vaccines will not only result in immune effects, but will increase the virulence of the virus and spread the virus.
The quality, transportation, storage, and use of the vaccine are inappropriate. For example, swine fever vaccine should be stored and transported at -15°C, and freezing and thawing should not be repeated. However, the grass-roots distributors mostly use the freezer at 0°C for preservation. Repeated freezing and thawing phenomena are common and the quality and potency of vaccines will be greatly reduced.
Affected by the immune body, the animal's immune response to vaccination antigens is genetically controlled to a certain extent, and each has its own differences. Even if the same species and different individuals, the immune response to the same vaccine is also inconsistent, there is a congenital immune deficiency that leads to immunity failure.
Affected by external stress factors, the body's immune function is regulated by nerves, body fluids and endocrine to a certain extent, under the influence of stress factors such as environmental overcooling, overheating, humidity, crowding, sudden feed changes, transportation, and crowding. The secretion of adrenocorticotropic hormone in the body increases and severely damages lymphocytes. In this case, vaccination weakens the immune system; or it is in the incubation period of infectious diseases, which often leads to death after inoculation.
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