1, extensive feed management, poor health level of pigs.

The low nutritional level of compound feed fed by pigs leads to malnutrition or chronic diseases and parasitic diseases. Excessive or lack of vitamins and trace elements will lead to impaired immune function. For example, vitamin A deficiency leads to atrophy of lymphoid organs, decrease of T lymphocytes and decrease of phagocytic ability of phagocytes. Adding proper amount of vitamin E or selenium to the diet can enhance immunity. At the same time, it can improve fertility and reduce hoof disease.

2, veterinary health and epidemic prevention work is not enough.

Pig farms pay attention to prevention, but ignore the environment. Piggery disinfection, serious illness isolation, blockade, corpse disposal, defecation treatment and so on can not meet the corresponding requirements, so that pathogens can spread and the epidemic situation expands.

3. The technical level of veterinarians is not high.

Some epidemic prevention personnel in pig farms have not received professional training, ignoring theoretical knowledge learning and strict technical operation. In the practice of preventive injection, it is necessary to know the health status, age, pregnancy time and local epidemic situation of pigs; At the same time, understand the quality of the vaccine. Use, transportation and storage should meet the requirements. All links must be strictly controlled, and a slight mistake will make the immunization fail. Such as: after piglet paratyphoid injection, poor spirit, no eating, vomiting, convulsions. Personal dose increases 1 fold, leading to shock and even death.

4, inoculation equipment disinfection is not complete.

Under normal circumstances, vaccination requires a shot and a change to avoid cross-infection.

5. The vaccine fails due to improper dilution operation or long storage time.

Diluent requires pH 6.8 ~ 7.4. If acid or alkali is used in the process of use, the live bacteria will die and the vaccine titer will be reduced or invalid. The diluted vaccine should be used in time at a temperature of about 65438 05℃. 15 ~ 25℃, used up in 6 hours; Above 25℃, use it up within 4 hours.

6. Long-term poisoning and detoxification of pigs with chronic or recessive diseases

Long-term poisoning and detoxification of pigs with chronic or recessive diseases are the main reasons for immune failure.

Sows are infected with classical swine fever during pregnancy, and the virus will destroy the immune cells of the fetus and damage its immune function. Because of the existence of these classical swine fever virus carriers, classical swine fever virus is easy to be infected, and piglets become infected pigs and virus-free pigs after birth.

It is very dangerous to inject swine fever attenuated vaccine into sows in the first month of pregnancy, which will cause sow reproductive disorder syndrome.

In the late stage of the implementation of the plan to eliminate classical swine fever, countries such as Europe and the United States banned classical swine fever vaccines, especially live vaccines, so as not to cause intrauterine infection and stimulate the occurrence of atypical mild classical swine fever.

7, maternal antibody interference makes immunity fail.

After the preventive injection of classical swine fever vaccine, there are antibodies in immunized sows, and piglets get maternal antibodies by sucking colostrum, which is passively protected for a certain period of time. The antibody level was 1: 64 ~ 128, and the immunity was strong, and then it gradually decreased to 60 days old and disappeared. The lower the maternal antibody titer, the better the immune effect. Generally speaking, suckling piglets are considered to be 20-25 days old after the first immunization and 60-65 days old after the second immunization.

In pig farms threatened by classical swine fever, pre-breast immunization (pre-immunization) is implemented, that is, suckling pigs are injected with 2ml of attenuated classical swine fever vaccine immediately after birth, and can breastfeed after 1.5 hours, and then the immunization is strengthened when they are 60 ~ 65 days old. Intramuscular injection of 2 ~ 4 doses can solve the interference problem of maternal antibody of swine fever virus in piglets.

8. Improper drug use leads to immune failure.

When using attenuated vaccines (such as swine pneumonia, swine erysipelas, piglet paratyphoid attenuated vaccine, etc.). ), 10 days should avoid using sulfonamides and antibiotics. Because of the antibacterial effect of drugs, live vaccines have no effect; It can also inhibit the proliferation of B lymphocytes, reduce white blood cells and affect the level of immune response. When there are antibiotics in feed additives, appropriate inactivated vaccine should be used first, not attenuated live vaccine.

9, the influence of mycotoxins in feed

Under the condition of high temperature and high humidity, mold often grows in grain feed, releasing mycotoxin and inhibiting immune function. Pesticide residues in feed also have an impact, which will also produce lymphocyte toxicity and lead to immune failure.

10, immunization is too frequent.

At present, infectious diseases in large and medium-sized pig farms are increasing day by day, and viral diseases and bacterial diseases are cross-infected, with a high incidence. In order to take countermeasures, most pig farms use more vaccines to control infectious diseases, which makes grass-roots veterinarians overworked and causes needle flying and needle leakage from time to time. The immune system of pigs is always in a state of nervous tension. Every vaccination is a negative period of disease resistance, and it takes some time to produce an immune response. Frequent injections will fatigue the immune system and reduce the immune effect.

1 1, there is no scientific immunization program.

The immunization program should be formulated according to the local epidemic situation, the occurrence of infectious diseases in this field, the immune status of pigs, the quality of employees and the actual situation of feeding management. Conditional pig farms should monitor the maternal antibody level of classical swine fever to determine the first immunization time. Regularly monitor serum antibodies such as porcine pseudorabies virus and porcine reproductive and respiratory syndrome virus. To determine the immunity of pigs and provide basis for making immunization plan. The immunization of pigs should be carried out according to the season, age, sex and incidence. Such as: sow immunization, 1: 5 12, 15 days old piglets antibody titer decreased to 1: 64, the protection rate was100%; The titer of antibody decreased to 1: 32 at the age of 20 days, and the protection rate was 75%. 30-day-old antibody titer is 1: 16, and there is no immunity. Immediate injection of swine fever vaccine can control the occurrence of swine fever. It is very important to monitor the level of maternal antibody and make the immunization program scientifically.