Origination and consequences of bovine viral diarrhea virus diversity.

The potential consequences of BVDV genetic and antigenic diversity are far ranging. The complexity of clinical presentations associated with BVDV likely arises from factors encoded by the virus genome. More importantly,prevention and control of BVDV may be complicated by diagnostic and immunization failure resulting from virus diversity. Evolutionary pressures will continue to drive further diversity, making control of BVDV challenging. Current and the potential for future BVDV strain diversity should be considered when designing BVDV control programs both at the individual farm and national herd level.     

Diagnosis of natural exposure to bovine viral diarrhea in a vaccinated herd by measuring extended antibody titers against bovine viral diarrhea virus

Two abortions occurred in a 150-head commercial cow-calf herd. Bovine viral diarrhea was suspected and confirmed by measuring extended titers against bovine viral diarrhea virus (BVDV) in a sample of 15 breeding females. Fifteen were sero-positive and 11 had significantly high titers (1:972-1:8748), likely due to natural exposure to cattle persistently infected with BVDV.     

Incidence of diarrhea among calves after strict closure and eradication of bovine viral diarrhea virus infection in a dairy herd.

OBJECTIVE: To determine whether strict closure of a dairy herd and eradication of bovine viral diarrhea virus (BVDV) infection would decrease incidence of diarrhea in calves during the first 31 days after birth, whether specific risk factors were associated with incidence of diarrhea in calves, and whether diarrhea was associated with weight gain of the calves. DESIGN: 2-year cohort study. ANIMALS: 448 calves. PROCEDURE: Calves were monitored from birth to 31 days of age. Fecal samples were tested for rotavirus, blood samples were tested for BVDV and antibodies to BVDV, and serum samples were tested for IgG concentration. Risk factors were evaluated by means of survival analysis. RESULTS: Incidence of diarrhea in calves decreased significantly after strict closure of the herd and eradication of BVDV infection. Risk factors for diarrhea in calves interacted in a multifactorial way. Rotavirus infection and low serum IgG concentration increased the risk that calves would develop diarrhea. Calves that developed diarrhea gained significantly less weight than calves that did not develop diarrhea. CLINICAL IMPLICATIONS: To control diarrhea among calves in a dairy herd, emphasis should be on maintaining a strictly closed herd free from BVDV infection. However, other measures, such as measures to prevent rotavirus infection and to ensure that calves receive an appropriate amount of colostrum after birth, should also be taken.     

Identification and eradication of bovine viral diarrhea virus in a persistently infected dairy herd.

A milking herd consisting of 55 Holstein cows had experienced abortions in several cows, as well as congenital malformations in 1 newborn calf. Bovine viral diarrhea virus was isolated from blood mononuclear cell samples obtained from several cattle, documenting 1 acute infection and 8 persistently infected carriers identified by clinical appearance and laboratory testing. Initial suspicion of persistently infected status in some, but not all animals, was facilitated by poor growth rates in some calves. Virus isolation was performed on transtracheal wash fluid obtained from acutely and persistently infected cattle with respiratory tract infection. We describe the measures taken to identify and characterize the infecting virus strain, and the series of actions taken to identify and eliminate persistently infected carriers in a herd experiencing several related problems that were shown to be caused by bovine viral diarrhea virus.     

Efficiency of various cloned DNA probes for detection of bovine viral diarrhea viruses.

We have evaluated 24 cytopathic (CP) and 37 noncytopathic (NCP) strains of bovine viral diarrhea virus (BVDV) with a dot blot assay using four different genome segments of the NADL strain as hybridization probes (p80, p54, gp53, and gp62). The p80 and p54 probes hybridized to 23/24 (96%) and 22/24 (92%), respectively, of CP strains examined. In contrast, these same two probes only detected 16/37 (43%) and 5/37 (13%), respectively, of the NCP strains examined. The gp53 probe detected 18/24 (75%) and the gp62 probe detected 19/24 (79%) of the CP strains. In contrast, these latter two probes only detected 9/37 (24%) and 7/37 (20%), respectively, of NCP strains. This low detection rate of NCP strains suggests a need for developing a probe based on NCP sequences for identification of NCP strains.     

Diagnostic investigation of bovine viral diarrhea infection in a Minnesota dairy herd

Bovine viral diarrhea (BVD) virus infection was diagnosed in neonatal calves with enteritis. Successful diagnostic procedures included direct immunofluorescence of frozen tissue sections, histopathology, and virus isolation. Virus isolation from buffy coats and serum was successful in detecting infected animals, whereas direct immunofluorescence of buffy coat samples was found to be less reliable. Virus was not isolated from any fecal samples. Booster vaccinations and the culling of animals shedding virus resulted in improved calf viability in this herd. It is suggested that procedures for the diagnosis of BVD virus infection should always be included in the diagnosis of neonatal calf enteritis.     

Reproductive consequences of infection with bovine viral diarrhea virus.

Reproductive efficiency is imperative for the maintenance of profitability in both dairy and cow-calf enterprises. Bovine viral diarrhea virus is an important infectious disease agent of cattle that can potentially have a negative effect on all phases of reproduction. Reduced conception rates,early embryonic deaths, abortions, congenital defects, and weak calves have all been associated BVDV infection of susceptible females. In addition, the birth of calves PI with BVDV as a result of in utero fetal exposure is extremely important in the perpetuation of the virus in an infected herd or spread to other susceptible herds. Bulls acutely or PI with BVDV may bea source of viral spread through either natural service or semen used in artificial insemination. Management practices including elimination of PI cattle, biosecurity measures and strategic use of vaccination can be implemented to reduce the risk of BVDV related reproductive losses.Development of vaccines and vaccine strategies capable of providing better protection against fetal infection would be of benefit.     

Investigation of bovine viral diarrhea virus infections in a range beef cattle herd

Bovine viral diarrhea virus (BVDV) infections resulting in clinical disease developed in calves, despite vaccination of dams and high maternal BVDV antibody titers in calves. Eight persistently infected (PI) calves born to immunocompetent dams were identified in the herd. Neutralizing BVDV antibody titers of PI calves had decreased greatly by the time the calves were 1 to 2 months old. Antibody titers of PI calves decreased more rapidly than antibody titers of calves that were not PI. Reduced antibody titers in PI calves allowed detection of BVDV in serum specimens of all PI calves by the time they were 8 weeks old. Persistent infection in suspect calves was detectable serologically and was confirmed by virologic examination of serum specimens 4 months after weaning, when the calves were 9 months old. Growth rates were reduced in viremic calves.     

Phylogenetic analysis and characterization of Korean bovine viral diarrhea viruses

Thirty-six bovine viral disease viruses (BVDVs) were identified in bovine feces (n = 16), brains (n = 2), and aborted fetuses (n = 18) in Korea. To reveal the genetic diversity and characteristics of these Korean strains, the sequences of their 5′-untranslated regions (5′-UTRs) were determined and then compared with published reference sequences. Neighbor-joining phylogenetic analysis revealed that most of the Korean viruses were of the BVDV subtypes 1a (n = 17) or 2a (n = 17). The remaining strains were of subtypes 1b (n = 1) and 1n (n = 1). This analysis indicates that the 1a and 2a BVDV subtypes are predominant and widespread in Korea. In addition, the prevalence of BVDV-2 was markedly higher in aborted fetuses than in other samples and was more often associated with reproductive problems and significant mortality in cattle.     

Differences in virulence between two noncytopathic bovine viral diarrhea viruses in calves.

A noncytopathic bovine viral diarrhea virus (BVDV), BVDV-890, isolated from a yearling heifer that died with extensive internal hemorrhages, was compared for virulence in calves with noncytopathic BVDV-TGAN, isolated from an apparently healthy persistently infected calf. After challenge exposure with BVDV-890, nonimmune calves (n = 7) developed fever > 40 C, diarrhea, leukopenia, lymphopenia, neutropenia, and thrombocytopenia. Most calves (n = 6) died or were euthanatized by 19 days after challenge exposure. Challenge exposure with BVDV-890 did not induce disease in 2 calves that had congenital persistent infection with BVDV or in 3 calves that had neutralizing antibody titer > 4 against BVDV-890. After challenge exposure with BVDV-TGAN, nonimmune calves (n = 7) developed fever > 40 C and, rarely, diarrhea or lymphopenia. All of those calves survived challenge exposure. The average maximal titer of BVDV-890 isolated from serum was 1,000 times that of BVDV-TGAN. In calves infected with BVDV-890, the average maximal percentages of lymphocytes and platelets associated with virus were greater than those found in calves infected with BVDV-TGAN. Additional findings of epidemiologic significance were prolonged shedding of virus and delayed production of viral-neutralizing antibody in 1 calf challenge-exposed with BVDV-890. Also, after production of neutralizing antibody, mutant virus that was refractory to neutralization was isolated from calves challenge-exposed with BVDV-TGAN.     

牛病毒性腹泻病毒E^rns基因的真核表达及抗原性检测

为研究牛病毒性腹泻病毒（BVDV）E^rns基因的生物学功能，将含有牛病毒性腹泻病毒E^rns基因的质粒pMD18-T—EE^rns经BamHⅠ／HindⅢ双酶切，获得了E^rns片段，再与杆状病毒转移栽体pBlueBaeHis2A连接，构建成重组质粒。将重组质粒pBlueBaeHis2A-E^rns与Bac-N—Blue^TMDNA共转染至sf9昆虫细胞中，获得了重组病毒，经噬斑筛选纯化，感染sf9昆虫细胞进行表达。SDS-PAGE分析结果表明，表达的目的蛋白大小约30ku；Western-blotting检测表明，该蛋白具有良好的抗原性。     

Tween 80: a marker for differentiation of hog cholera and bovine viral diarrhea viruses.

Markers for differentiating hog cholera and bovine viral diarrhea viruses were studied using Tween 80, chloroform, trichlorotrifluoroethane and tri (n-butyl) phosphate. Attenuated A and virulent Ames strains of hog cholera virus were employed. Moreover, the NADL PK-15 cell culture adopted strain and low cell culture passaged Purdue strain of bovine viral diarrhea virus were used. These viruses were reacted with 2,500 micrograms/ml of Tween 80 for one hour at 37 degrees C. When attenuated A and virulent Ames strains of hog cholera virus with titers greater than 10(6) and 10(5) plaque forming units respectively, were reacted with Tween 80 the titer of each strains was reduced by approximately 10(4) plaque forming units of virus. When either strain of bovine viral diarrhea virus was reacted with Tween 80, virus was not detected.     

Characterization of a panel of monoclonal antibodies and their use in the study of the antigenic diversity of bovine viral diarrhea virus

A panel of 40 monoclonal antibodies (MAb) specific for bovine viral diarrhea virus (BVDV) was produced, and each MAb was characterized and grouped according to its viral protein specificity, immunoglobulin subclass, virus-neutralizing activity, and immunoreactivity with a large collection of BVDV isolates. The MAb were found to be specific for 1 of 3 sets of related viral-induced proteins found in cells infected with the Singer strain of BVDV. Group-1 MAb were specific for the 80- and 118-kilodalton (kD) proteins of BVDV. Group-2 MAb recognized 3 proteins with molecular sizes of 54, 56, and 58 kD. Group-3 MAb recognized a 43- and a 65-kD protein. The MAb belonged to either the IgG1, IgG2a, IgG2b, IgG3 subclasses or the IgE class of mouse immunoglobulin. All MAb in group 2 were able to neutralize BVDV and had neutralization titers that ranged from 24 to 1,600,000. The reactivity of the MAb with numerous field isolates of BVDV was highly variable. Both cytopathic and noncytopathic biotypes of BVDV were examined and had the same degree of antigenic variation. The greatest degree of variation was detected with group-2 MAb. The data demonstrate that BVDV isolates have a high degree of antigenic variation that is largely confined to the envelope glycoproteins associated with virus neutralization. The results also suggest that antigenic variability of this virus is important in the development and severity of the disease it causes.     

An immunodiffusion test for detection of bovine viral diarrhea virus antibodies in bovine serum.

An immunodiffusion test (IDT) was developed for detecting bovine viral diarrhea virus antibodies in bovine serum. The antigen utilized in the IDT was prepared from bovine viral diarrhea virus-infected monolayer cultures. Results of the IDT were obtained within 48 hours and correlated with the virus-neutralization test.     

猪源牛病毒性腹泻病毒套式PCR检测方法的建立

根据GenBank中BVDV-1、BVDV-2、CSFV及新出现瘟病毒的基因序列,设计2对特异引物,建立了能鉴别诊断BVDV与CSFV的Nested-PCR检测方法;确定其方法的特异性、敏感性、稳定性。建立的Nested-PCR能从BVDV标准毒株、猪源BVDV毒株中扩增198bp特异性片段,对猪瘟病毒、猪繁殖与呼吸综合征病毒检测结果为阴性。结果表明,该方法具有较好特异性;其敏感性可检测到0.195fg RNA模板量;经重复性试验表明该方法具有良好稳定性。初步应用检测表明,猪BVDV阳性率较高,达36.0%;牛血清及其制品、猪瘟活疫苗BVDV污染严重。本试验建立的Nested-PCR具有敏感、特异和稳定等特点,可用于临床诊断和流行病学调查。     

Some antigenic and cultural properties of border disease and bovine viral diarrhoea viruses

In vitro comparison of the replication cycles of three strains of border disease virus and one strain of bovine viral diarrhoea virus showed similar growth curve patterns and a tendency of cell-free virus to exceed cell-associated virus. Each virus was antigenically distinguishable from the others in cross-neutralisation tests.