1. Immune characteristics of PRRSV.
1.The PRRSV NSP2 genetic variant modulates the host immune response;
2.Antibody-dependent enhancement effect (ADE).
3.The theory that "weak immunity promotes virus mutation". PRRSV mutates to evade immunity under low cellular immunity or antibody immune pressure, and the acceleration of accurate measurement of viral mutation increases by 480%, and the virus mutation changes from "slow" to "running".
4.The structural protein (SP) of the NADC30-like strain had poor immunogenicity and low levels of induced antibodies
5.The NADC30-like strain CHSX1401 has a strong immune evasion ability, which can effectively activate inflammation and host immune system and promote the persistence of the disease.
2. On the development and application of PRRS vaccines
6.In 1994, Boehringer Ingleheim developed the world's first live PRRS vaccine.
7.In 1997, Bayer developed the first inactivated PRRS vaccine.
8.Up to now, there are 4 inactivated PRRS vaccines and 5 live PRRS vaccines in EuropeThere is 1 inactivated PRRS vaccine and 5 live PRRS vaccines in the Americas.
9.In 2007, the first live PRRS vaccine (CH-1R strain) was developed in China.
10.Up to now, a total of 2 inactivated PRRS vaccines, 7 live attenuated PRRS vaccines and one genetically engineered chimeric vaccine have been approved in China.
3. Key points of PRRS management and future vaccine prospects
11.Minimize the number of gilts** (promote closed-loop production): 3 months or more of closed group management, testing and isolation, immune acclimation;
12.Control the management of pig herd flow within the farm;
13.Two-point production, all-in and all-out, and fetal management;
14.PRRS immunization management: vaccine selection and immunization program (PRRS unstable field 2 consecutive live vaccine immunization + piglets need to be transferred out two months after immunization, and it is more prudent to use inactivated vaccine immunization in the future breeding herd).
15.Advocate virus detection and selection of vaccines, and inactivated vaccines can choose type immunization;
16.Gilts are domesticated using on-site serum or attenuated vaccines;
17.Biosecurity: group clearance + partial group clearance, foster care within 24 hours, elimination of sick and weak pigs, needlepoint management, etc.;
18.PRRS monitoring: formulate a systematic sampling plan and testing plan, and collect oral fluid for PCR detection as much as possible
19.The use of antibiotics and high-quality Chinese medicine for health care, Chinese medicine can be used at the beginning of PRRS disease, during the disease, and after recovery, with the main focus on protecting the lungs in the early stage, clearing heat in the middle stage, and improving immunity in the final stage.
20.At present, new deletion, insertion, and mutation strains of PRRSV and recombinant strains are constantly emerging, and the evolution rate of PRRSV is accelerating. This is related to the imperfect biosecurity measures of most pig farms in China, resulting in the transmission of PRRSV, the introduction of toxic breeding pigs, and the non-standard use of live attenuated PRRS vaccine. Therefore, the prevention and control strategy of blue ear in pig farms is an important measure to prevent this disease.
21.PRRSV is a complex genetic variant, and mutant viruses inevitably arise due to the lack of RNA-dependent RNA polymerase (RDRP) of the virus3 5 correction function, which cannot correct the base mutations that occur during PRRSV replication. The recombination between different strains has exacerbated the genetic variation of PRRSV and promoted the diversification of PRRSV strains.
22.It is important to attach great importance to the fact that insufficient immunity will promote the mutation of the virus. Therefore, immunization of inactivated seedlings after the use of live seedlings or serum is a reliable option for breeding farms. When immunity is not strong, some mutations that are conducive to immune escape are retained in the process of antagonistic host innate immunity of the virus, which will promote the rapid mutation of the virus.
23.Porcine reproductive and respiratory syndrome virus (PRRSV) vaccination is widely used to control clinical disease, but in some cases it is not as effective. In Belgium, there have been field reports of sows routinely inoculated with PRRSV but seronegative ELISA: ELISA does not respond. IDEXX ELISA (ELISA 1) and CIVTeS ELISA (ELISA 2) were used to detect PRRSV-specific antibodies in 1400 sows from 70 PRRSV-vaccinated sow herds to assess the prevalence of ELISA non-response. Quantification of neutralizing antibodies (NABS) in viral neutralization assays. Univariate logistic regression was used to identify population risk factors for the presence of ELISA non-response. The herd prevalence of non-responding pigs was 35% to 4The prevalence varies between 1%, 40% at the population level, and between 5% and 20% (ELISA 1) and 5% to 30% (ELISA 2). The neutralizing antibody (NABS) of ELISA non-responding pigs was significantly lower than that of ELISA responding pigs. The risk of ELISA non-response was significantly reduced in herds using a combination of a modified live vaccine and an inactivated vaccine.
Part of the information in this article**: He Dongsheng, "Practical Research and Prevention and Control of PRRS".