| Background:Brucellosis is an acute or chronic contagious zoonosis caused by Brucella. It was identified as one of the noticeable diseases and categorized in Class II by the Law on Prevention and Control of Infectious Diseases of the People’s Republic of China. In fact, it is one of the most severe zoonosis worldwide,especially in the developing countries.The complicated cardinal clinical signs of Brucellosis make it difficult to differentiate it from other common diseases with fever or other inflammatory damages. And if misdiagnosed,it would bring great pain to patients.Since the 1950s, China has done many researches on the epidemic situation, epidemiological characteristics,etiology and pathogenesis of Brucellosis.According to CDC China,,the number of new cases of human Brucellosis increased 57% from 2008 to 2013, with a rapid annual growth rate of 10%; and the newest data of 2014 showed that the case had increased to 57,222,increasing 34.8% over the same period of 2013.In northern China,including Inner Mongolia, Heilongjiang, Hebei, Shanxi, Jilin,and Xinjiang provinces,the incidence is up to 50-1395/100,000, which has also lead to enormous economic losses. Thus, the prevention and control of humanBrucellosis is quite severe, pressing and significant.Brucella are facultative intracellular bacteria,it mostly parasites within two host cell types, macrophage and placental trophoblasts.Natural reservoir of Brucella and the infection sources in humans include infected domestic animals, mainly cattle, sheep, goats and swine.Dogs, especially shepherd dogs, and wild animals:hares, wild rabbits, roe deer and foxes may also play some role as reservoirs and spreaders of Brucella.Nowadays Brucella are classified into ten species,including B. melitensis,B. abortus,B. suis,B. canis.B. ovis,B. neotomae,B. microti,B. pinnipidialis,B. cetand B. inopinata.Pathogen of human Brucellosis mainly includes B. melitensis, B. abortus,B. Suis,and almost 80% is B. melitensis..The major factors of brucellosis in China are animal abortions such as sheep fetuses and placenta;milk and its production;animal meat and entrails;animal carcasses;under certain condition such as farms where there are infected animals,some other factors of transmission including dust, soil and water are also quite important.Brucella could invade human body by various routes,mainly including infected animal and its meat exposure,Brucella could also invade body via alimentary tract,respiratory tract and lesion skin.Long-term high consumption of meat, dairy products,engaging in some food and fodder processing may result in Brucella infection among some individuals.According to "Blood stations technology operating rules (2012 edition)", hepatitis B virus(HBV), hepatitis C virus9(HCV), human immunodeficiency virus (HIV),treponema pallidum and ALT screening must be processed.Therefore,human brucellosis hazard the the general population in cities and towns in daily life,the infection rate of non-profession population is increasing yearly.On the other hand,the case reports of human brucellosis person to person transmission are increasing daily including mother infant vertical transmission,blood transfusion and sexual contact transmission.Some detailed pathogenic mechanism,serologic assay, nucleic acid testing and other diagnostic assay have been showed but the transfusion-transmitted Brucella infection was ignored.Blood products was in a state of low temperature,with the exception of syphilis, malaria, hepatitis, etc,other pathogens were often neglected.At 4 ℃ and lack of appropriate culture,Brucella could survive for 6 months.The first transfusion-transmitted brucellosis has been described since the 1950s;in addition,blood products antibody positive rate were as high as 3.6%at Mexico blood center in 2004.In some endemic area,20% of patients were in a state of undiagnosed,made the blood safety in the potential risk.The prevalence or the case report of blood-transmitted brucellosis has not yet carry out formally in the northern of China,which is the brucellosis epidemic areas.However,increasing incidences of person to person transmission and other related transmission show the significance to pay attention to the blood safety.Blood donation screening for the brucella is important to the prevention,detection and diagnosis of blood-transmitted brucellosis,controlling the person to person brucellosis transmission effectively. Kashi area of Xinjiang locates in the northwest of China,it is a multi-ethnic-populated areas,the majority of the population is Uighur (90%) and other ethnicities.Kashi areas is rich in natural resources,agriculture and animal husbandry is the primary industry in the region,which is the main financial resource.Animal husbandry’s rapid development,more and more frequent, cross-regional,multi-channel livestock trading result in the more purchases of infected animals.At the same time,the inspection and quarantine mechanism of the animals is not sound,leading to input and output of the infectious source.On the other hand, the backward economy,poor living conditions,lacking protection awareness increase the chance of infection.The potential risk of blood-transmitted brucellosis is increasingly outstanding on account of natural economic structure,eating habits and characteristics and the various transmission routes.At present, serological detection combined with nucleic acid testing is the best for transfusion transmitted disease screening.The epidemic areas especially the northern epidemic areas of China,the clinical evaluation of blood-transmitted brucellosis and effective screening for brucella in blood donation on a greater scale can improve the safety of blood products,prevent and reduce blood-transmitted brucellosis;on the other hand,it can also provide helpful information for the nucleic acid testing applied to the screening.Aims:The study evaluating Brucella infection in blood donors in Kashi areas of Xinjiang is to put forward the potential risk of blood transfusion-transmitted brucellosis and the increasingly non-professional infected population.The data will provide helpful information for the importance and necessity of screening of blood safety evaluation in endemic area of China. Methods:1. The research object and material:Experimental group was 3896 blood donor samples collected in Kashi central blood station,Xinjiang,China.A negative control group of 399 blood samples was collected from Shenzhen blood center,where brucellosis is nonendemic.2. The research methods:(1) Primary screening:All donors passed the predonation questionnaire and had no brucellosis history.All plasma samples passed the rapid predonation testing for HBsAg and ALT.(2) Double checkrAll plasma samples were then routinely screened for HBsAg,HCV,HIV-1/2 and syphilis.Only samples which were not reactive for serologic tests and normal ALT were tested for Brucella infection screening.(3) Brucella infection screening:All qualified blood samples plasma were primitively for antibody to Brucella by the Rose Bengal plate test(RBPT).Then the reactive samples were tested by the standard tube agglutination test (SAT) and for antibody capture, using native membrane protein extracts (NMPs) of B.Melitensis enzyme-linked immunosorbent assay (ELISA).The ELISA-reactive samples were confirmed by Western blot with recombinant BP26 or OMP31. Seropositive samples were tested with qPCR for Brucella DNA.The qPCR-reactive samples were further tested with a nested PCR using three sets of primers specifically targeting the BP26 gene of Brucella,Then the amplicons were purified,sequenced.In addition,some seropositive samples were follow up in the experimental group.Results:1. Serologic testingA total of 135(3.5%) RBPT positive blood samples were tested by SAT in parallel and 120(3.1%) were positive.Among 135 RBPT positive blood samples,there were 39(1.0%) reactive with NMPs of B.Melitensis and 25(0.64%) of 39 ELISA-positive samples reactive with rBP26 or rOMP31 using Western Blot,and the former’s reactivity was stronger than the latter’s.2. Follow-up blood samplesThere were only two follow-up blood samples(No.43 and 115) obtained from blood donors 145 and 110 days after the index blood samples collection respectively.Both blood samples were reactive to RBPT and SAT,however the blood culture were both negative for Brucella isolation.Donor sample 43 were reactive to rBP26 and rOMP31 by Western Blot,but sample 115 were both negative.Although there were two different serological testing results,the follow-up blood samples were reactive and confirmed by Brucella DNA detection.3. Nucleic acid testing14(0.36%) blood samples showed evidence of Brucella DNA by qPCR,13 of them were confirmed containing Brucella-specific BP26 DNA fragments by nested PCR.In addition to the two follow-up blood samples,there were totally 15(0.39%) Brucella DNA-positive samples.4. Detection methods compareAmong 15 Brucella-DNA positive samples,the detection rate of RBPT,SAT,ELISA,Western-Blot and qPCR was 100%,87%,3%,40% and 87% respectively.The pathogen positive rate showed 11.1%,10.8%,30.8%,28.0% and 92.9%,respectively,suggesting that,despite its poor specificity,RBPT could be primary screening assay.5. Brief epidemiologic surveyAccording to statistics,between January 1,2010, and May 5,20135Kashi central blood station totally collected 40,502 blood donations.The positive rate of HBsAg,anti-HCV,anti-HIV and anti-syphilis was 0.42%,0.51%,0.16% and 0.44% respectively,and plusing nearly 0.9% prevalence of HBsAg from the predonation blood donors,the overall HBsAg prevalence was 1.3%.In this study,approximately 3.5% of blood donations were reactive to Brucella antibody assays,0.64% were serologically confirmed by Western blot and 0.39% molecularly confirmed by nested PCR amplification.According to the chi-square test,Brucella infected men were higher than women;Han blood donors(36%) were more susceptible to infections than Uighur and other ethic groups;4%-5% donors’ age between 35-45 years among the RBPT or SAT-positive blood samples;although direct implication of occupational risk was found in 18% to 40% of Brucella infections.Conclusion1. Approximately 3.5% of blood donations in Kashi areas were reactive to Brucella antibody assays,and 0.39% molecularly confirmed by NAT,suggesting potential risk of blood transfusion-transmitted brucellosis among non-professional populations in Kashi,Xinjiang of China.2. It suggested that in the Brucella-endemic areas, Brucella screening should be carried out in blood donors.The evaluation for transfusion-transmitted brucellosis in more aspects investigation in blood donors are recommended in the endemic areas of Brucella infection of China,which could provide helpful information to prevention and control transfusion-transmitted brucellosis.3. RBPT was mainly recommended methods for primary screening of Brucella infection because of its high sensitivity,simple operation and low cost.Nucleic acid testing combined with RBPT could check out bacteremia of Brucella infection,reducing the blood and blood products loss in Brucella-endemic areas of China. |
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