牛病毒性腹泻病（BVD）对牧场生产的直接影响

上海两个牧场因出现后备牛生长发育迟缓、腹泻、死亡,成乳牛流产等现象,在确认患牛BVDV抗体阳性后,随后对两场育成牛进行了病毒性腹泻抗原检测,共发现BVDV持续感染牛(PI牛)51头,占总测试育成牛总数2.53%,在随后的半年里对持续感染牛进行了隔离跟踪观察,发现奶牛感染BVDV对牧场的经济损失较大,除了牧场常见的腹泻、流产等现象外,BVDV可造成后备牛发育不良,观察结果表明持续感染牛平均比正常牛要轻83.67kg,每月月增重比正常牛要少4.9kg,18月龄以上育成牛的繁殖率中,PI牛繁殖率仅为16.7%,而正常牛为83.3%,其中2头已经产犊,此外,在PI牛中也出现了7头死亡,1头育成牛因屡配不孕而淘汰,PI牛在观察期间的淘汰率为15.69%,可见,牛病毒性腹泻病的存在可给牧场造成极大的经济损失,因此,牧场必须关注此病,尽早进行检测持续感染牛和净化BVD.     

牛病毒性腹泻病毒检测方法研究进展

牛病毒性腹泻病(bovine viral diarrhea, BVD)是由牛病毒性腹泻病毒(Bovine viral diarrhea virus, BVDV)感染导致的传染病。该病会导致牛生产性能下降,给全球养牛业带来严重的经济损失。BVD的临床表现和病理变化与其他牛源腹泻病毒病相似,因此有必要根据不同的条件选择快速高效的BVDV诊断方法,及时采取措施阻断BVDV在牛群间、BVDV持续感染牛(persistently infected, PI)与健康牛之间传播,减少BVDV对养牛业造成的经济损失。用于BVDV检测的方法很多,主要有病毒分离鉴定、荧光定量RT-PCR、RT-PCR、环介导等温扩增技术(LAMP)、重组酶聚合酶扩增技术(RPA)、胶体金免疫检测技术(GICT)、酶联免疫吸附试验(ELISA)、抗原捕获ELISA(AC-ELISA)、间接免疫荧光法(IFA)等。近年一些新兴技术和优化的方法被应用于BVDV的检测,如抗体液相芯片技术、CRISPR-LwCas13a系统、双重纳米RT-PCR法等,均具有特异性强和灵敏度高等优点。作者从抗原、抗体两个方面总结了BVDV检测方法的研...     

上海地区规模化牧场IBR流行情况调查

为了解上海地区规模化牧场荷斯坦奶牛的牛病毒性腹泻(BVD)、牛传染性鼻气管炎(IBR)的感染情况,使用ELISA检测方法对19个规模化牧场的BVDV血清抗原、IBRV血清抗体进行检测。共检测BVDV、IBRV血清样品920份,并结合以上牧场的饲养管理、生产疾病等资料数据进行分析。检测结果表明BVDV抗原阳性率平均为3.70%,IBRV抗体阳性率为46.74%。     

上海地区奶牛两种病毒性疾病血清学调查

本研究对上海地区多个规模化牧场荷斯坦牛的牛病毒性腹泻(BVD)和牛传染性鼻气管炎(IBR)血清学感染情况进行调查。使用ELISA检测方法对19个规模化牧场共920份血清样品进行BVDV血清抗原、IBRV血清抗体检测,并结合这些牧场的饲养管理、繁殖、疾病等资料数据进行分析。检测结果表明BVDV抗原阳性率平均为3.70%,IBRV抗体阳性率为46.74%。     

北京地区规模化奶牛场牛病毒性腹泻病血清学调查

对北京郊区6个未进行牛病毒性腹泻病（BVD）免疫牛场的546份奶牛血清样品,使用牛病毒性腹泻抗体ELISA试剂盒进行检测,并对其中3个牛群进行牛病毒性腹泻病毒（BVDV）血清抗原筛查。共检出阳性血清514份,总阳性率94.1%,其中5个牛场的场内血清抗体阳性率在95%以上。牛病毒性腹泻持续性感染牛（PI牛）筛查的3个牛群均有阳性牛检出。结果表明,北京地区规模化奶牛场存在牛病毒性腹泻感染和接触史,应采取净化措施进行控制。     

BVDV对后备牛生长发育状况及繁殖性能的影响

牛病毒性腹泻/黏膜病(BVD/MD)是一种严重危害奶牛健康的病毒性传染病,其病原为牛病毒性腹泻病毒(BVDV)。BVDV感染牛后主要表现两种状态,即一过性感染(TI)和持续性感染(PI)。BVD在牛场的流行,可严重影响奶牛的生产性能、繁殖性能及牛群健康状况,对奶牛的影响可表现为流产、胎儿畸形、腹泻和免疫抑制等。怀孕母牛在特定妊娠阶段感染BVDV后,可娩出PI犊牛,部分PI犊牛能像正常犊牛一样生长发育至成年,但其生长发育状况和繁殖性能较同龄健康牛差异十分明显。为评价BVDV对后备牛生长发育及繁殖状况的影响,笔者采用ELISA方法检出北京地区28个规模化奶牛场141头BVDV-PI牛,并与同龄健康牛生长发育及繁殖数据相比较,结果表明,BVDV-PI后备牛各月龄段的体高、体重均低于健康后备牛,其首次输精日龄、配准日龄、耗精量明显高于健康后备牛,而一次情期受胎率显著低于健康后备牛。数据显示,BVDV严重影响后备牛的生长发育及繁殖状况。     

北京地区奶牛场牛传染性鼻气管炎、牛病毒性腹泻病风险评估及流行情况分析

本研究对北京地区中小奶牛场及养殖小区进行了牛传染性鼻气管炎(IBR)、牛病毒性腹泻病(BVD)的风险评估.结果表明,参试牛场及小区的后备牛IBR血清阳性率达50.52％,BVD血清抗体阳性率达70.98％;从牛场水平看,24个牛场中IBR抗体场间阳性率达到50％ (12/24),BVD抗体场间阳性率达到87.50％(21/24),IBR高风险牛场9个,BVD高风险牛场12个,双高风险牛场7个.此次评估结果表明,北京地区IBR流行情况较为严重,应考虑疫苗免疫;参试的大部分牛场有BVDV的急性感染史或接触史,高风险牛场应启动BVDV清除计划.     

江苏规模化奶牛场BVD与IBR流行病学调查

为了解江苏地区规模化奶牛场牛传染性鼻气管炎(IBR)及牛病毒性腹泻病(BVD)流行与分布情况,采用商品化酶联免疫吸附试验(ELISA)试剂盒对来自江苏省7个市和不同地区的13个大型规模化奶牛养殖场共540份血清中IBRV抗体进行检测,采用商品化ELISA试剂盒对来自江苏省5个市和不同地区的11个大型规模化奶牛养殖场共460份血清中BVDV抗体进行检测,同时从中随机采集100份血清样本,采用巢式逆转录聚合酶链式反应(nRTPCR)进行BVDV抗原检测与基因分型。结果表明:不同牛场的BHV-Ⅰ抗体阳性率为0%~82.1%%,平均阳性率为21.1%(114/540);不同牛场的BVDV抗体阳性率为0%~98%,平均阳性率为51.5%(237/460);不同牛场的BVDV抗原阳性率为0%~100%,平均阳性率为55%(55/100);对相应样本的BVDV抗原与抗体检测结果进行比较表明,抗原~+/抗体~+牛占40%(40/100),抗原~+/抗体~-牛占15%(15/100),抗原~-/抗体~-牛占35%(35/100),抗原~-/抗体~+牛占10%(10/100);基因分型结果显示,BVDV-Ⅰ型占11%(6/55),BVDV-Ⅱ型为78%(43/55),Ⅰ型与Ⅱ型混合感染占11%(6/55),未发现BVDV-Ⅲ型。研究表明,BVDV和BHV-Ⅰ在江苏省主要规模奶牛场普遍流行,但不同地区、不同牛场的阳性率存在明显差异,大部分牛场均能检测出抗原~+/抗体~-的持续感染牛,BVDV含基因Ⅰ、Ⅱ型,但主要以Ⅱ型感染为主。     

牛病毒性腹泻病对牧场生产的直接影响

上海2个牧场出现后备牛生长发育迟缓、腹泻、死亡,成母牛流产等现象,在确认牛病毒性腹泻病（BVD）抗体阳性后,对这2个牧场育成牛进行了病毒性腹泻抗原检测,共发现持续感染牛（PI牛）51头,占总测试育成牛的2.53%。在随后的半年里,对持续感染牛进行了隔离、跟踪观察,发现BVD牛给牧场带来的经济损失较大。除了牧场常见的腹泻、流产等现象外,BVD可造成后备牛发育不良。观察结果表明,持续感染牛平均比正常牛轻83.67kg,每月月增重比正常牛少4.9kg;18月龄以上育成牛中,PI牛繁殖率仅为16.7%,而正常牛为83.3%。此外,在PI牛中也出现了7头死亡,1头育成牛因屡配不孕而被淘汰,持续感染牛在观察期间的淘汰率为15.69%。可见,牛病毒性腹泻病给牧场造成极大的经济损失,因此,牧场必须关注此病,尽早进行检测和净化。     

河南省规模化奶牛场牛病毒性腹泻流行病学调查

为了解河南省奶牛场牛病毒性腹泻(BVD)的流行情况,本试验采用酶联免疫吸附试验(ELISA)方法对2019年12月—2020年9月采集的河南省40个规模化奶牛场5 486份血清进行检测。结果显示：河南省奶牛场5 486份血清中,BVDV抗原阳性率为1.77%;泌乳牛、后备牛和犊牛的BVDV抗原阳性率分别为1.73%、2.31%和1.12%;豫东、豫南、豫西、豫北和豫中地区的BVDV抗原阳性率分别为1.16%、3.49%、1.62%、1.59%和1.48%,豫东和豫南地区间BVDV抗原阳性率差异显著(P<0.05);不同年龄间BVDV抗原阳性率差异不显著(P>0.05)。由此可见,河南省奶牛场存在BVDV感染,其中豫南地区的BVDV感染率最高,后备牛的BVDV感染率最高。     

一步法RT-PCR检测血清混合样品在BVDV清除计划中的应用

利用一步法RT-PCR对58份BVDV抗原阳性血清进行检测。试验证明,对OD450=0.3的标准血清,该方法的最低检出限为5μL/头,血清混合检测时至少可将60份OD450〉0.3的阳性血清等量混合。此外,RT-PCR与ELISA-Ag联合使用时,数学推导证明当混合样品为10～30个/份时,BVDV清除计划检测成本最低,相比单独使用ELISA-Ag,成本至少下降70%。综上,本试验确立的一步法RT-PCR灵敏度高,特异性好,联合ELISA-Ag使用,可大幅降低BVDV清除计划的检测成本,故值得推广使用。     

BVDV infection risk in the course of the voluntary BVDV eradication program in Styria/Austria

A total of 1362 persistently BVDV-infected animals were identified in 850 herds during the first 3 years of the voluntary BVDV eradication program in Styria/Austria. Within the same period of time, the prevalence of BVDV-infected herds dropped from 7.3% to 2.2% of the 4412 herds covered by the program. The relative BVDV infection risk decreased at least four-fold in herds on common grazing and at least five-fold in herds which purchased cattle during the first 30 months of the BVD control program. Thus, the relative BVDV infection risk was reduced by between five to nine times of the initial risk following the implementation of the 3-year eradication program in all herds participating in the program.     

Establishing a pilot bovine viral diarrhoea virus eradication scheme in Somerset

Beginning in April 2006, 41 farms were recruited onto a pilot Bovine viral diarrhoea virus (BVDV) eradication programme across the south of England with the majority of study herds concentrated in Somerset. Each herd was assessed and where relevant cleared of persistently infected (PI) animals. Seven farms dropped out before whole herd screening could be performed. Of the remaining 34 farms, 20 (59 per cent) were classified as infected although two of these were initially misclassified as BVDV-free. Over the course of three years, 61 PIs were identified across 16 of the 20 infected farms. 72 per cent of PIs indentified on the first herd test were below two years of age. PI prevalence ranged from 0.2 to 3.1 per cent of infected herds and was highest in herds that did not vaccinate. By the end of 2009, 24/34 (71 per cent) of study farms were BVDV-free while 10 (29 per cent) remained infected.     

奶牛场病毒性腹泻清除计划的实施

对北京某牛场977头牛采用抗原捕获ELISA方法进行牛病毒性腹泻病毒持续感染牛的筛查,共检出8头阳性牛,其中后备牛7头、成母牛1头。在后续新生犊牛检测中检出1头阳性犊牛。后备持续感染牛表现不同程度的发育迟缓,配种延迟,与国外报道一致。以抗原检测为手段的持续感染牛的清除计划,可用于奶牛场病毒性腹泻的清除与控制。     

Epidemiological Study of Pestiviruses in South American Camelids in Switzerland

Background: In the context of the ongoing eradication campaign for bovine viral diarrhea virus (BVDV) in cattle in Switzerland, the role of South American camelids (SAC) as a possible virus reservoir needed to be evaluated. Objective: To assess and characterize the prevalence of pestivirus infections in SAC in Switzerland. Animals: Serum samples collected from 348 animals (40 herds) in 2008 and from 248 animals (39 herds) in 2000 were examined for antibodies against pestiviruses and for the presence of BVDV viral RNA. Methods: Cross‐sectional study using stratified, representative herd sampling. An indirect BVDV‐ELISA was used to analyze serum samples for pestivirus antibodies, and positive samples underwent a serum neutralization test (SNT). Real‐time RT‐PCR to detect pestiviral RNA was carried out in all animals from herds with at least 1 seropositive animal. Results: In 2008, the overall prevalence of animals positive for antibodies (ELISA) and pestiviral RNA or was 5.75 and 0%, respectively. In 2000, the corresponding prevalences were 3.63 and 0%, respectively. The seroprevalences (SNT) for BVDV, border disease virus or undetermined pestiviruses were estimated to be 0, 1.73, and 4.02% in 2008, and 0.40, 1.21, and 2.02% in 2000, respectively. Conclusions and Clinical Importance: At the present time, SAC appear to represent a negligible risk of re‐infection for the BVDV eradication program in cattle in Switzerland.     

Predicted costs and benefits of eradicating BVDV from Ireland

Bovine viral diarrhoea virus (BVDV) causes an economically important endemic disease (BVD) of cattle in Ireland and worldwide. Systematic eradication by detection and removal of infectious (BVDV carrier) cattle has been successful in several regions. We therefore assessed the benefits (disease losses avoided) and costs (testing and culling regime) of a potential eradication programme in Ireland. Published bio-economic models of BVDV spread in beef suckler herds and dairy herds were adapted to estimate potential benefits of eradication in Ireland. A simple model of BVDV spread in beef finisher herds was devised to estimate the benefits of eradication in this sector. A six year eradication programme consisting of 5 inter-related virological and serological testing programmes is outlined and costed. We found that the annualised benefits of BVDV eradication in Ireland exceeded the costs by a factor of 5 in the beef suckler sector and a factor of 14 in the dairy sector. Corresponding payback periods were 1.2 and 0.5 years respectively. These results highlight the significant economic impact of BVDV on the Irish cattle industry and suggest a clear economic benefit to eradication using the proposed approach. This type of cost-benefit analysis is considered an essential prerequisite prior to undertaking an eradication campaign of this magnitude.     

Control of bovine viral diarrhea/mucosal disease in the district of Kamenz on a voluntary basis--ways, successes, limitations

In 69 dairy and beef herds in the district of Kamenz, Saxony, with a total number of 21,783 and 89.6% of the district's cattle, a voluntary BVDV eradication protocol was implemented from 2000 to 2007. The aim was to achieve eradication as comprehensive as possible and to prepare the herds for the mandatory eradication program. Essential preconditions for the accreditation of a herd as "free of BVD virus" were the antigen test of all cattle and their offspring for 12 months including completeness check and a negative serological random sampling of young cattle. Mean eradication period of infected herds lasted 45.6 months, herd size, and the number of newly purchased cattle were found to have a significant influence. In five infected farms calf losses significantly decreased after termination of the eradication. further examination of the 126 antigen test positive animals from 15 herds resulted in 87 persistently infected (PI) and 15 transiently infected (TI) individuals, 24 animals missed the second test. Furthermore, out of the 87 PI's 30 individuals (34%) had antibodies against BVDV. Eight farms vaccinated their whole herd, seven only the young stock before first breeding, and 54 herds did not vaccinate, respectively. Concluding from this study, the epidemiological particularities of the farms should be taken in account. Testing of all cattle in a minimum of time including, official monitoring of immediate culling of PI's, immediate epidemiological research, and serological monitoring of the eradication process is necessary.     

Control of BVDV-infection on common grassland--the key for successful BVDV-eradication in Lower Austria

A bovine viral diarrhea/mucosal disease (BVD/MD) control and eradication program was introduced in Lower Austria in 1996, according to the Swedish model. At present 9800 out of 17,000 herds are part of this program. An important risk factor for BVDV-transmission under local conditions is communal grazing. Approximately 3-4% of livestock share common pastures, in which susceptible pregnant cattle may be mixed with unrecognised persistently infected (PI) animals. Rules and regulations were defined to allow only herds free from BVDV-infection on to common grassland. At the moment, 5067 herds are certified free from BVDV. The percentage of BVDV-free herds in regions with intensive pasture utilisation is higher (57.3%) than in the other regions (43.0%) of Lower Austria. With a reliable system for identification of PI-animals and a high certainty of prevention of PI-animals on common grassland, the main transmission of BVDV infection can be stopped, even if the animals are derived from infected herds and transiently infected animals cannot be excluded.     

Test strategies in bovine viral diarrhea virus control and eradication campaigns in Europe.

Several European countries have initiated national and regional control-and-eradication campaigns for bovine viral diarrhea virus (BVDV). Most of these campaigns do not involve the use of vaccines; in Germany, vaccination is used only in states in which it is considered necessary because of high BVDV prevalence. In European countries without organized BVDV control programs, vaccination is commonly used to control BVDV. Diagnostic test strategies are fundamental to all control-and-eradication campaigns; therefore, the purpose of this review is to describe how the available diagnostic tests are combined into test strategies in the various phases of control-and-eradication campaigns in Europe. Laboratory techniques are available for BVDV diagnosis at the individual animal level and at the herd level. These are strategically used to achieve 3 main objectives: 1) initial tests to classify herd status, 2) follow-up tests to identify individual BVDV-infected animals in infected herds, and 3) continued monitoring to confirm BVDV-free status. For each objective or phase, the validity of the diagnostic tests depends on the mode of BVDV introduction and duration of infection in test-positive herds, and on how long noninfected herds have been clear of BVDV. Therefore, the various herd-level diagnostic tools--such as antibody detection in bulk milk or in blood samples from young stock animals, or BVDV detection in bulk milk--need to be combined appropriately to obtain effective strategies at low cost. If the individual diagnostic tests are used with due consideration of the objectives of a specific phase of a BVDV control program, they are effective tools for controlling and eradicating BVDV in regions not using vaccination and where vaccination is a part of the control or eradication program.     

一步法RT—PCR检测大缸奶在BVDV清除计划中的应用

本文利用一步法RT—PCR对28个牛场共计50份大缸奶样进行了BVDV核酸检测。在与全群抗原检测结果对比后发现．9个已知存有PI牛的泌乳牛群,其大缸奶核酸检测均为阳性,其余41个已知无PI牛的泌乳牛群．除1个因为存在急性感染牛造成阳性结果外,其余40个均为阴性。由此可见,本方法对与泌乳牛群内是否存在PI牛可以做出准确判断,其检测灵敏度和特异性均为100％,阳性预测结果可信度为0．9（9／10）,阴性预测结果可信度为0．98（40／41）。此外．针对50个大缸奶样进行的抗体检测表明,对于已感染牛场,泌乳牛群是否存在PI牛,抗体水平没有明显差异（OD1．12±0．12vsOD1．34±0．23,P〉0．05）。实验室条件下,本试验使用的RT—PCR方法对于阳性乳的最低检出限为50uL/头,因此理论上,最多可从1000份样品中检出阳性乳成分（总体积为50mL）。综上可知,本试验确立的RT—PCR方法灵敏度高、特异性强,可对泌乳牛群是否存在PI牛进行准确预测,相比大缸奶抗体检测更具实际指导意义,联合ELISA—Ag使用时还可大幅度降低泌乳牛群BVDV清除计划的检测成本,因而值得推广使用。