| Brucellosis is a worldwide zoonosis caused by Brucella species.In recent years,the disease remains a significant economic and public health problem with the rapid development of the breeding industry of cattle and sheep and the frequent transportation of live animals and their products.The epidemiological investigation of brucellosis in cattle and sheep was carried out to grasp the current situation and prevalence rate of the epidemic,so as to lay a foundation for further prevention,control and purification of brucellosis.In the past,brucellosis detection methods were relatively simple due to limited experimental conditions.According to the national standard,the Rose Bengal test(RBT)is used for screening,and the serum agglutination test(SAT)is used for diagnosis.In recent years,some rapid detection methods such as competitive enzyme-linked immunosorbent assay(cELISA)and colloidal gold immunochromatography assay(GICA)have been developed.Therefore,it is imperative to study the efficiency of rapid detection methods.This study compared different detection methods to screen the most simple and fast detection methods.According to “National plan for the prevention and control of brucellosis(2016-2020)”,the prevention and control of brucellosis in China should be managed in a regional way,which can be divided into three types of regions,and our province belongs to class I.According to the “Work plan for the prevention and control of brucellosis in Shandong province”,Qingdao,Weihai and Yantai are the non-immune areas of brucellosis,and measures of detection and purification should be taken.The remaining 13 cities were immunized areas,which should be tested and immunized.In 2018,S2 vaccine of pig brucella was widely used for the first time in our province to immunize cattle and sheep.But the relevant data on the immune effect in our province is still not clear.For this reason,the immune effect of this vaccine was tested in this study.This study investigated the prevalence of brucellosis of bovine and sheep in Shandong province in 2019,aiming to provide scientific basis for the comprehensive prevention and control measures of brucellosis in Shandong province.In 2019,a total of 22,212 samples ofnon-immune serum from cattle and sheep were collected from 474 farms in 16 cities in Shandong province.Among them,11,675 non-immune serums were collected from 219 cattle farms and 10,537 non-immune serums from 255 sheep farms.After testing,56 positive samples were found in 15 farms,with a positive rate of 0.48% for individuals and 6.85% for groups.9 positive samples were detected from 3 farms,with a positive rate of 0.09% for individuals and 1.18% for groups.Further analysis showed that the positive samples of bovine and sheep brucellosis came from 18 farms in 7 cities.From the perspective of space,it is mainly distributed in the west and central region of Shandong.From the perspective of season,the peak of brucellosis of cattle and sheep was in spring.In terms of population,brucellosis of cattle occurred in small-scale farms with a stock population of 100-500,and brucellosis of sheep occurred in farms with a stock population of more than 100.The common methods of serological detection for brucellosis are different in sensitivity and specificity,as well as in simple,easy and rapid operation.In this study,four serological methods,RBT,SAT,cELISA and colloidal gold,were compared to analyze the sensitivity,specificity and coincidence rate of the four detection methods and then to screen the more suitable serological test methods.Four methods were used to detect 648 samples of bovine and sheep serum(including 328 samples of bovine serum and 320 samples of sheep serum).The results showed that the coincidence rates of SAT,RBT,cELISA and colloidal gold were all high(85%~90%).Colloidal gold has a low specificity,but it is easy to operate and can be used in the field detection during transportation.cELISA has the highest sensitivity and is easy to operate in the laboratory.It can be used for laboratory testing in the prevention,control and purification of brucellosis.In order to evaluate the immune effect of S2 vaccine,we used colloidal gold,RBT and cELISA to detect the positive rate of cows and sheep immunized with S2 vaccine.Follow-up monitoring was carried out on the 7th day,15 th day,30 th day,60 th day,90 th day,150 th day and 180 th day respectively.The results showed that both cows and sheep could detect brucellosis antibody on the 7th day.The antibody positive rate was the highest on the 15 th day in cow immune and the highest on the 30 th day in sheep.After 150 days of immunization,the antibody positive rate was lower than 10%.180 days later,all sheep turned negative,and only2% of cows did not turn negative.In the meantime,we also detected the changes of IFN-γ andIL-10 in serum after immunization.The content of IL-10 and IFN-γ in serum of S2 vaccine test group was slightly higher than control group,and changed with the extension of immunization time.The content of IFN-γ in serum of dairy and sheep test group was significantly higher than control group(p < 0.05)from 15 th to 30 th day after immunization.S2 vaccine can stimulate dairy and sheep to produce specific antibody IFN-γ against Brucella.Our study has mastered the individual and population positive rate of brucellosis in Shandong province in 2019,as well as the distribution in space,time and population.We defined the sensitivity,specificity and coincidence rate of the four detection methods,SAT,RBT,cELISA and colloidal gold.Meanwhile,we found out the positive rate of antibodies at different time points after ingested the S2 vaccine in cows and sheep,so we know that cows and sheep could be test out after immunization one year. |
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