| Brucellosis is a zoonotic infectious disease that not only causes significant economic losses to the animal husbandry industry,but also seriously endangers public health and safety.In recent years,brucellosis has become more common in the world and has gradually expanded.A safe and efficient brucellosis vaccine is still in the research and development stage.Although the attenuated brucellosis vaccine plays a key role in the prevention and control of the brucellosis,the vaccination of the attenuated vaccine has caused interference in the serological testing of brucellosis,It hinders the quarantine and elimination process of diseased animals and latently infected animals,and the immune effect of Brucellosis attenuated vaccine when immunizing animals is closely related to the vaccination route and the dose of vaccination.The mechanism of the production of protective antibodies after the Brucellosis attenuated vaccine is immune to the body is not yet complete clear.To understand the prevalence of sheep and goat brucellosis in some provinces of China and the vaccination status of brucellosis vaccine.This study conducted a serological survey of sheep and goat brucellosis in some provinces(regions)in China from 2017 to 2019,and established a highly effective and accurate serological screening program for brucellosis.The experimental results show that combined with the flock vaccine immunization procedure and the exclusion of sheep after natural infection,the combined detection of the three serological methods can effectively detect the seropositive sheep with sera antibodies.The survey results show that the total positive rate of 2183 sheep serum(RBPT)tests from 6 provinces(regions)is35%,the total positive rate of(i-ELISA)test is 21%,both(RBPT)and(i-ELISA)tests The positive rate of positive sheep serum(c-ELISA)test was 79%.The total positive rate of 2008 sheep serum brucellosis antibodies in four northern provinces(regions)was 13.45%,and the total positive rate of 175 sheep serum brucellosis antibodies in two southern provinces(regions)was 2.86%.Among them,the total positive rate of975 sheep serum brucellosis antibodies in large-scale farms was 8.62%,the total positive rate of 521 sheep serum brucellosis in breeding cooperatives was 15.43%,and the total number of 687 sheep serum brucellosis antibodies from herders or farmers the positive rate was 16.30%.Brucella suis S2 strain vaccine is currently the main attenuated veterinary brucellosis vaccine in China.In order to better understand the dynamic changes of various aspects of the body in the short term after the S2 strain vaccine immunizes sheep,it is better understand and master the immune protection mechanism of attenuated brucellosis vaccine.The sheep in the experimental and control groups were monitored for body temperature before and after immunization,tissue load measurement,serum tiger red plate agglutination test(RBPT),serum brucellosis antibody competitive enzyme-linked immunosorbent assay(c-ELISA),and cytokine IL-6.IL-12 p70,IFN-γ indirect enzyme-linked immunosorbent assay(i-ELISA),paraffin sections of lymphoid tissues and HE staining,etc.After immunizing sheep with Brucella suis(S2 strain)vaccine statistical analysis of changes.The results showed that,within 9 days of vaccine immunization,the overall temperature fluctuation of sheep showed an upward trend,and the temperature fluctuation of 10-30 days was small,which was stable.Serum(RBPT)test results show that the serum antibody of Brucellosis presents a process that first rises to a certain level,then maintains for a period of time and then gradually declines At 7 and14 days after immunization,Brucella was isolated only in some submandibular lymph node tissues of sheep,while Brucella was not isolated in the sampling tissues of sheep at other time points.It may be because the live bacteria in the host tissue are cleared by the body’s immune system as the time after immunization increases,and no live bacteria can be detected.After immunization,the expression level of IL-6 associated with Brucella infection in sheep increased continuously from 0 to 30 days,and the expression level of IL-6 gradually decreased in sheep from 30 to 90 days after immunization.The expression levels of IL-12 p70 and IFN-γ gradually increased within 30-90 days after immunization,and the expression levels of these two cytokines did not fluctuate much from 0-30 days after immunization.Observation of tissue sections showed no obvious nodular lymph node structure and no obvious medulla in the lymph tissue of the sheep in the control group,and the overall number of lymphocytes was normal.In the experimental group,only obvious nodule structure and obvious nodular germinal center can be seen.When the body is stimulated by the antigen,the germinal center of lymph nodules increases rapidly,and the number of lymphocytes and lymph nodules changes with the time of immunization. |
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