一起奶牛腹泻病的病原学诊断

辽宁省某奶牛养殖场10～30日龄犊牛发生腹泻,为查明病因,我们对送检的18份犊牛腹泻样本分别进行牛轮状病毒(BRV)、牛冠状病毒(BCoV)、牛病毒性腹泻病毒(BVDV)、产肠毒素大肠杆菌(ETEC)、沙门氏菌(Salmonella)和安氏隐孢子虫(C. andersoni)的PCR检测。结果显示:18份犊牛腹泻样本中,BRV、BCoV、BVDV的检出率分别为83.3%(15/18)、88.9%(16/18)、61.1%(11/18),这3种病原的混合感染率较高,其他病原均未检出,说明该奶牛场的犊牛腹泻主要由BRV、BCoV、BVDV混合感染引起。     

河南省2021-2022年犊牛腹泻主要病原流行情况调查

为了解河南省2021-2022年犊牛腹泻病原流行情况,利用犊牛腹泻病原微生物核酸检测试剂盒（荧光PCR法）分别对2021年河南省20余家牧场送检的170份犊牛腹泻样品,2022年送检的112份犊牛腹泻样品进行牛轮状病毒（BRV）、牛冠状病毒（BCoV）及大肠杆菌K99+(E.coli K99+)荧光PCR检测,并对检测结果采用SPSS 27.0软件进行数据统计以及显著性差异分析（Pearson卡方检验）。结果显示：2022年BRV检出率为50.00%、BCoV检出率为41.00%,相比2021年均显著增高(P<0.01),E.coli K99+检出率与上一年相比基本持平,无明显差异（P>0.05）,说明2022年BRV、BCoV流行情况愈加严重。进一步分析发现,2022年腹泻病原单一感染检出率为26.79%,其中主要是BRV感染,与2021年单一感染检出率25.29%基本持平,差异不显著（P>0.05）。2022年腹泻病原混合感染检出率为35.71%,且主要以BRV、BCoV混合感染为主。相比2021年的12.94%明显上升,差异显著（P<0.01）,说明202...     

河北省唐山市奶犊牛病毒性腹泻流行病学调查

试验旨在掌握河北省唐山市13个县（市、区）奶牛场奶犊牛病毒性腹泻病原的流行状况,有效防控奶犊牛腹泻。采集唐山市不同地区38个奶牛场腹泻犊牛粪便样品788份,提取腹泻粪便样品中的基因组RNA。根据GenBank公布的牛病毒性腹泻病毒（Bovine viral diarrhea virus,BVDV）E2基因、牛轮状病毒（Bovine rotavirus,BRV）VP6基因、牛冠状病毒（Bovine coronavirus,BCV）N基因序列,利用Primer Premier 5.0软件分别设计特异性引物,采用PCR方法检测粪便样品中这3种基因,利用Excel 2007对不同地区、不同季节和混合感染病原检测结果进行汇总分析。在采样范围内的788份犊牛腹泻粪便样品中,BVDV、BRV和BCV阳性检出率分别为29.82%（235/788）、29.44%（232/788）和18.02%（142/788）;在所有被检地区,滦南县BVDV感染率最高,阳性检出率为45.38%（59/130）,汉沽区BRV和BCV感染率最高,阳性检出率分别为55.00%（22/40）和37.50%（15/40）;从采样季节来看,春季、夏季和秋季BRV感染率最高,阳性检出率分别为27.71%（46/166）、39.58%（114/288）和19.89%（39/196）,冬季则以BVDV感染为主,阳性检出率为52.17%（72/138）;从混合感染情况来看,以BRV＋BCV二重混合感染为主,感染率为8.37%（66/788）。河北省唐山市各地区腹泻犊牛群中均存在BVDV、BRV和BCV感染,以BVDV、BRV单一感染为主。     

犊牛轮状病毒和大肠杆菌混合感染检测

黑龙江省某规模化奶牛场部分新生犊牛发生了严重腹泻且犊牛病死率较高。为了确诊,无菌采集病料,通过病毒检测、细菌分离、生化试验、细菌和病毒特异性基因PCR扩增、动物致病性试验及药敏试验等方法进行了病毒抗原和微生物检测。结果显示,病毒检测中牛轮状病毒（BRV）呈阳性,PCR扩增得到400 bp的特异性片段;从病料中分离到1株含K99和F41兼性菌毛抗原的高致病性产肠毒素大肠杆菌（ETEC）,该分离菌株对恩诺沙星、头孢唑啉、氯霉素敏感,对其他抗生素有一定的耐药性。流行情况调查结合病原学检查确诊该牛场新生犊牛严重腹泻是由BRV和大肠杆菌混合感染造成的,根据诊断结果进行了针对性地防制,取得了良好的防控效果。     

犊牛轮状病毒病的诊断和防控

牛轮状病毒(bovine rotavirus,BRV)又称犊牛腹泻病毒(calf djarrha virus),属于呼肠孤病毒科(Reoviridae)轮状病毒属(Rotavirus).轮状病毒感染多发生在15～45日龄的犊牛,其临床症状表现为精神沉郁、食欲废绝、水样腹泻、严重脱水和酸中毒.犊牛轮状病毒病是牛轮状病毒引起的犊牛的急性肠道传染病.该病在世界范围内造成严重的经济损失.从犊牛轮状病毒的病原学、流行病学特点、临床症状和诊断等几个方面进行阐述,以期为综合防控该病提供参考.     

牛轮状病毒疫苗及被动免疫抗体研究进展

牛轮状病毒(bovine rotavirus, BRV)是集约化养殖中犊牛腹泻的重要致病原之一。BRV是一种二十面体对称的双链RNA病毒,其基因组含有多种结构蛋白和非结构蛋白,并分为众多血清型,流行型多为G6和G10型,具有较强的致病性。目前,国内BRV的商品化疫苗和针对性治疗产品仍处于市场空白阶段。随着养牛业的蓬勃发展,对于BRV的防治已经迫在眉睫。对BRV的结构特点、传播途径、以及养牛业发达国家市场上的BRV疫苗上市情况和BRV卵黄抗体的研究进程进行综述,旨在为下一步疫苗和抗体的研发应用提供一定的参考。     

牛轮状病毒引起的犊牛腹泻研究进展

犊牛腹泻是养牛场饲养管理过程中面临的最主要的奶牛健康问题之一,危害主要表现为饲料利用率下降、治疗成本增加以及不同程度的死亡率,可造成严重的经济损失。牛轮状病毒(Bovine rotavirus,BRV)是引起犊牛腹泻的最主要病原,7日龄以内犊牛最为易感。产毒素性大肠杆菌和牛冠状病毒也是引起犊牛腹泻的病因,而牛冠状病毒对环境的耐受力弱,临床上很少发生,大肠杆菌可使用抗生素进行控制,因此,临床上引起犊牛腹泻发生率最高的是BRV。对牛轮状病毒进行免疫预防已成为控制犊牛腹泻的关键环节。本文结合国内外研究进展,阐述牛轮状病毒引起的犊牛腹泻的发生、诊断以及免疫预防和控制,为犊牛腹泻综合防控措施的建立提供基础。     

我国牛轮状病毒的分离鉴定和疫苗研究进展

约50%的犊牛腹泻是由牛轮状病毒(Bovine Rotavirus, BRV)引起的,它制约着我国养牛业的发展.论文综述了牛轮状病毒毒株的分离、鉴定方法及疫苗研制的现状,并对BRV新型疫苗的发展趋势进行了展望.     

青海西宁牦牛病毒性腹泻疫病病原学调查与分析

为掌握青海省西宁市牦牛群中病毒性腹泻疫病各种致病原的流行情况,本试验采用RT-PCR方法对西宁市74份腹泻牦牛粪便样品进行了BVDV、BRV、BEV、BCV、BAstV的病原学检测与分析,结果显示:西宁市大部分地区均存在BVDV、BRV、BEV、BCV、BAstV的流行,以湟源县的流行最为严重,BVDV、BRV、BEV、BCV、BAstV平均阳性感染率分别为37.84%、27.03%、22.97%、5.41%、2.70%,以BVDV的感染最为严重。共存在BVDV、BRV、BEV、BAstV 4种单感型以及BVDV/BRV、BVDV/BEV、BVDV/BCV、BRV/BEV、BRV/BCV、BVDV/BRV/BEV、BVDV/BRV/BCV 7种混感型,混合感染型较多,混合感染情况较复杂。表明青海省西宁市牦牛病毒性腹泻中存在多种致病原的单独感染以及混合感染,且混合感染现象严重,为西宁市牦牛病毒性腹泻疫病的综合防控积累了资料。     

牛病毒性腹泻病毒、大肠杆菌和奇异变形杆菌混合感染致犊牛腹泻的研究

为确定甘肃省临夏州某奶牛场犊牛腹泻的病因,并提供合适的治疗方案和防控措施,试验采集该牛场13头腹泻犊牛的粪便和血清,通过胶体金技术、ELISA方法、细菌分离鉴定、Kirby-Bauer法分别进行病毒病原学检测、病毒血清学抗体检测、病原菌鉴定和药物敏感性试验。病毒学检测结果显示,13份粪样中未检测出牛轮状病毒（BRV）、牛冠状病毒（BCV）的抗原,牛病毒性腹泻病毒（BVDV）抗原阳性率为23.08%（3/13）;未检出BRV和BCV的抗体,BVDV血清学抗体阳性率为38.46%（5/13）。病原菌检测结果显示,13份粪便样品中,分离出13株大肠杆菌和7株奇异变形杆菌。药敏试验表明,分离的大肠杆菌和奇异变形杆菌对20种常规药物均产生了不同程度的耐药,且无对两种细菌均有效的药物。此次犊牛腹泻是由BVDV、大肠杆菌、奇异变形杆菌混合感染引起的,且大肠杆菌和奇异变形杆菌的耐药现象严重,本试验结果为该牛场进一步治疗此次的犊牛腹泻病提供了合理有效的依据。     

A seroepidemiological study of the importance in cow-calf pairs of respiratory and enteric viruses in beef operations from northwestern Quebec.

Serum antibody analyses for bovine herpesvirus type 1 (BHV-1), bovine viral diarrhea virus (BVDV), bovine respiratory syncytial virus (BRSV), bovine coronavirus (BCV), and bovine rotavirus (BRV) were performed on 527 randomly selected cows, before calving, and on 407 three-week-old calves. In cows and calves, BCV and BRV were the most seroprevalent viruses (80% to 100% according to virus and vaccination status). Bovine respiratory syncytial virus was the least seroprevalent in the cows, independent of the vaccination status. In nonvaccinated cows the seroprevalence to BRSV was 36.7%, and 53.5% in cows vaccinated less than two weeks prior to collecting blood, and 67.6% in cows vaccinated two weeks or more prior to blood collection. In their calves, BHV-1 was the least seroprevalent, independent of the vaccination status. The serological status and antibody titers in calves were generally associated with those of the dam. The occurrence of respiratory diseases in the calves was associated with cow and calf serological profiles (BHV-1, BRSV and BCV in the nonvaccinated group, BHV-1, BVDV and BCV in the vaccinated group). The occurrence of diarrhea was not associated with cow and calf serological profiles but was negatively associated with high level calf serum IgG in the nonvaccinated group (odds ratio = 0.73). Bovine coronavirus and BRV were shed by 1.4% and 4.9% of calves in the nonvaccinated group, and by 0% and 9.9% of calves in the vaccinated group, respectively. Bovine rotavirus shedding was associated with fecal diarrheic consistency at the moment of fecal sampling but not with previous occurrence of diarrhea.     

Correlation between maternal serum antibodies and protection against bovine rotavirus diarrhea in calves

The correlation between maternal serum antibodies in beef calves at 2 days old and protection against diarrhea induced by natural bovine rotavirus (BRV) infection was examined. Virus neutralizing (VN) antibody titers against BRV in sera from calves that developed diarrhea by BRV infection within 14 days of age (BRV-diarrheal calves) were significantly lower than those from calves that had no diarrhea. In the BRV-diarrheal calves, a positive correlation was found between the VN antibody titers and age of the onset of diarrhea. There were negative correlations between the VN antibody titers and duration of the diarrhea, VN antibody titers and cumulative diarrhea scores, and the VN antibody titers and duration of virus shedding. These results suggest that the VN antibody titers against BRV in newborn calf serum could be an indicator of protection against BRV-induced diarrhea.     

Egg yolk IgY: protection against rotavirus induced diarrhea and modulatory effect on the systemic and mucosal antibody responses in newborn calves

Bovine rotavirus (BRV) is an important cause of diarrhea in newborn calves. Local passive immunity is the most efficient protective strategy to control the disease. IgY technology (the use of chicken egg yolk immunoglobulins) is an economic and practical alternative to prevent BRV diarrhea in dairy calves. The aim of this study was to evaluate the protection and immunomodulation induced by the oral administration of egg yolk enriched in BRV specific IgY to experimentally BRV infected calves. All calves in groups Gp 1, 2 and 3 received control colostrum (CC; BRV virus neutralization Ab titer - VN=65,536; ELISA BRV IgG(1)=16,384) prior to gut closure. After gut closure, calves received milk supplemented with 6% BRV-immune egg yolk [(Gp 1) VN=2048; ELISA IgY Ab titer=4096] or non-immune control egg yolk [(Gp 2) VN<4; ELISA IgY Ab titer<4] twice a day, for 14 days. Calves receiving CC only or colostrum deprived calves (CD) fed antibody (Ab) free milk served as controls (Gp 3 and 4, respectively). Calves were inoculated with 10(5.85)focus forming units (FFU) of virulent BRV IND at 2 days of age. Control calves (Gp 3 and 4) and calves fed control IgY (Gp 2) were infected and developed severe diarrhea. Around 80% calves in Gp 1 (IgY 4096) were infected, but they showed 80% (4/5) protection against BRV diarrhea. Bovine RV-specific IgY Ab were detected in the feces of calves in Gp 1, indicating that avian antibodies (Abs) remained intact after passage through the gastrointestinal tract. At post infection day 21, the duodenum was the major site of BRV specific antibody secreting cells (ASC) in all experimental groups. Mucosal ASC responses of all isotypes were significantly higher in the IgY treated groups, independently of the specificity of the treatment, indicating that egg yolk components modulated the immune response against BRV infection at the mucosal level. These results indicate that supplementing newborn calves' diets for the first 14 days of life with egg yolk enriched in BRV-specific IgY represents a promising strategy to prevent BRV diarrhea. Moreover a strong active ASC immune response is induced in the intestinal mucosa following BRV infection after the administration of egg yolk, regardless the specificity of the treatment.     

Prolonged excretion and failure of cross-protection between distinct serotypes of bovine rotavirus

Four newborn calves were experimentally infected with two distinct serotypes of bovine rotavirus (BRV-1 and BRV-2). Initially, three colostrum-deprived calves were inoculated orally with either BRV-1 or BRV-2; all developed severe diarrhea and produced serotype-specific neutralizing antibodies. Fecal virus was first demonstrated by immunofluorescence the day after inoculation. The virus titers reached a maximum of 10(5.2)-10(6.6) fluorescent focus forming units g-1 of feces 2-5 days after inoculation and then decreased. Fecal virus was detected in low titers beyond 28 days after inoculation despite the development of serum neutralizing antibodies. One calf, which had acquired specific active immunity against BRV-1 following oral infection, was further infected orally with BRV-2 4 weeks later. The calf again manifested diarrhea, excreted BRV-2 and showed an increase in serum neutralizing antibody against BRV-2. These results indicated that calves infected with either BRV-1 or BRV-2 do not have cross-protection to infection with heterologous BRV, and that recurrence of the disease can occur. The possible mechanisms of the persistence of BRV in calves and its role in the epidemiology of this infection are discussed.     

Rapid and sensitive detection of bovine coronavirus and group a bovine rotavirus from fecal samples by using one-step duplex RT-PCR assay

Bovine coronavirus (BCoV) and group A bovine rotavirus (BRV) are two of major causes for neonatal calf diarrhea. In the present study, a one-step duplex RT-PCR was established to detect and differentiate BCoV and group A BRV from fecal samples. The sensitivity of this method for BCoV and group A BRV was 10 PFU/100 μl and 1 PFU/100 μl, respectively. Twenty-eight diarrhea fecal samples were detected with this method, the result showed that 2 samples were identified as co-infected with BCoV and group A BRV, 26 samples were group A BRV positive, and 2 samples were negative. It proved that this method is sensitive for clinical fecal samples and is worth applying to laboratory diagnosis for BCoV and group A BRV.     

Effect of infection with bovine viral diarrhea virus alone,bovine rotavirus alone,or concurrent infection with both on enteric disease in gnotobiotic neonatal calves

OBJECTIVE: To compare experimentally induced concurrent infection with bovine viral diarrhea virus (BVDV) and bovine rotavirus (BRV) with infection of either virus alone in calves. ANIMALS: Seventeen 1-day-old gnotobiotic calves. PROCEDURE: Calves were allotted to 8 treatments as follows: group 1, mock-infected control calves (n = 2); group 2, inoculated with BVDV on day 1 (2); groups 3, 5, and 7, inoculated with BRV on days 1 (2), 4 (1), or 7 (2), respectively; and groups 4, 6, and 8, inoculated with BVDV on day 1 and with BRV on days 1 (2), 4 (2), or 7 (4), respectively. Concentrations of BVDV in serum and ileal tissues were measured, and BRV shedding in feces was determined. Histologic examination and immunohistochemical analysis were conducted to detect lesions and viral antigens. RESULTS: Neonatal calves inoculated with BVDV alone or with BVDV on day 1 and BRV on day 7 developed villus atrophy and submucosal inflammation of the intestines. Concurrent BVDV and BRV infections acted synergistically in the intestinal tract, causing more severe enteric disease than infection with either virus alone. Severe lymphoid depletion was associated with BVDV infection in calves regardlesss of concurrent BRV infection. CONCLUSIONS AND CLINICAL RELEVANCE: Infection with BVDV played direct and indirect roles in enteritis in neonatal calves, causing villus atrophy in the duodenum and submucosal inflammation of the intestines. Also, BVDV potentiated effects of BRV. Concurrent infection with BVDV and BRV resulted in more severe enteric disease in neonatal calves than infection with BRV or BVDV alone.     

一例冠状病毒、轮状病毒混合感染引起犊牛腹泻的诊治

2022年3月,河南省某规模化奶牛养殖场发生一起新生犊牛腹泻病例,在流行病学调查、临床症状观察、病理剖检的基础上,采集6头腹泻犊牛的新鲜粪便进行了寄生虫卵检查、小球隐孢子虫、牛轮状病毒、冠状病毒、大肠杆菌K99抗体检测,血液样品进行了牛病毒性腹泻病毒抗原检测,组织样品进行了细菌分离。结果表明牛轮状病毒抗原6头阳性,阳性率100%;冠状病毒抗原4头阳性、2头阴性,阳性率66.7%;其他病原均为阴性。根据临床症状、病理变化和实验室检测结果,确诊该病例为牛冠状病毒和轮状病毒混合感染引起的犊牛腹泻。根据诊断结果,采取了改善饲养管理、补液、收敛、止泻等综合性防治措施,疫情得到了有效的控制,为临床防治犊牛腹泻提供了参考。