Attenuation of a virulent type 2 bovine viral diarrhea virus

The purpose of this study was to produce an attenuated bovine viral diarrhea virus (BVDV) type 2 strain as a tool for identifying potential virulence markers in the BVDV2 genome. The attenuation of the virulent strain, BVDV2-24515, was accomplished by in vivo and in vitro passage. The strain was initially used to infect an elk (Cervus elaphus) [J. Wildl. Dis. 35 (1999) 671], re-isolated at 7 days post-inoculation from serum, and then subsequently passaged 56 times in cell culture. Two groups of calves were inoculated intranasally with either BVDV2-24515 or the putative attenuated virus, designated BVDV2-LATT. Calves inoculated with BVDV2-24515 had cumulative clinical scores which ranged from 6 to 53. Clinical signs in these calves consisted of anorexia, depression, dehydration, diarrhea (±bloody), and pneumonia. Several calves developed leukocytopenia, primarily a neutrocytopenia, and presented lesions of enteritis or pneumonia at necropsy. In contrast, cattle inoculated with BVDV2-LATT had cumulative clinical scores which ranged from 0 to 2. This was not significantly different from that of controls which received no virus (range: 0–1). Calves inoculated with BVDV2-LATT produced high neutralizing antibody titers against BVDV2. Thus, in addition to its potential use as a tool for identifying virulence markers, the attenuated virus is also worthy of further study as a candidate virus for inclusion in a modified-live vaccine.     

Expression of toll-like receptors and co-stimulatory molecules in lymphoid tissue during experimental infection of beef calves with bovine viral diarrhea virus of low and high virulence

The objective of this study was to compare the mRNA expression of Toll-like receptors (TLR3 and TLR7), and costimulatory molecules involved in activation of lymphocytes and antigen presenting cells (CD80, CD86, CD28, and CD40L) after experimental infection of beef calves with low or high virulence noncytopathic (ncp) bovine viral diarrhea virus (BVDV) strains. Thirty BVDV-naïve, beef calves were intranasally inoculated with low (LV; n?=?10, SD-1) or high (HV; n?=?10, 1373) virulence ncp BVDV or with BVDV-free cell culture medium (Control, n?=?10). Calves were euthanized on day 5 post-inoculation and tracheo-bronchial lymph node (TBLN) and spleen samples were collected for mRNA expression through quantitative-RT-PCR. Levels of mRNA for TLR3 and TLR7 were increased in spleen of HV group (P?mRNA was up-regulated in TBLN of both LV and HV groups (P?mRNA was observed in TBLN for LV calves (P?相似文献   

Prevalence and risk factors associated with bovine viral diarrhea virus infection in dairy herds in Jordan

A cross-sectional study was carried out to determine the seroprevalence and to identify risk factors associated with bovine viral diarrhea virus (BVDV) infection in 62 non-vaccinated dairy herds (671 cows) in Jordan between January and June 2007. Information regarding herd management was recorded through a personal interview with farmers. Antibodies against BVDV were detected using an indirect ELISA test. Chi-square analysis and multivariable logistic regression model were used to identify risk factors for BVDV seropositivity. The true prevalence of antibodies against BVDV in individual cows and cattle herds was 31.6% and 80.7%, respectively. The seroprevalence of BVDV in medium and large size herds was significantly higher than that in smaller herds. There was no significant difference in BVD seroprevalence between different age groups. Random-effects logistic regression model revealed two major factors associated with seropositivity to BVDV; exchange of visits between adjacent farm workers and not isolating newly purchased animals before addition to the herd. The seroprevalence of BVDV in cows located in the northern Jordanian governorates was significantly higher than that in other studied governorates. Results of this study indicated that BVDV is highly prevalent in Jordan and BVDV infection could be controlled by livestock-trade control, and applying strict biosecurity measures in the dairy farms.     

Experimental infection of early pregnant cows with bovine viral diarrhea virus: Transmission of virus to the reproductive tract and conceptus

The objective of this study was to chronologically investigate the effect of bovine viral diarrhea virus (BVDV) infection on early pregnant cows before placenta formation. Six cows were intravenously inoculated with either BVDV (treated, n = 4) or growth medium (control, n = 2) (day 0) at day 26 of pregnancy. Two treated cows and one control cow were euthanized on day 3 post-infection and the remaining animals were euthanized on day 6. BVDV was isolated from maternal tissues such as lymphoid or reproductive tissues of treated animals on days 3 and 6 post-infection. Additionally, one treated cow autopsied on day 6 post-infection had evidence of infectious BVDV in the allantoic membranes, allantoic fluid and embryos. In three treated cows, a significant decline in progesterone concentration was also observed post-infection while in control cows they remained constant. Therefore, BVDV can infect bovine embryos before placenta formation and may affect progesterone profiles in cows during early pregnancy.     

Effects in calves of mixed infections with bovine viral diarrhea virus and several other bovine viruses

The objective of this study was to verify whether a mixed infection in calves with bovine viral diarrhea virus (BVDV) and other bovine viruses, such as bovid herpesvirus-4 (BHV-4), parainfluenza-3 (PI-3) and infectious bovine rhinotracheitis (IBR) virus, would influence the pathogenesis of the BVDV infection sufficiently to result in the typical form of mucosal disease being produced.

Accordingly, two experiments were undertaken. In one experiment calves were first infected with BVDV and subsequently with BHV-4 and IBR virus, respectively. The second experiment consisted in a simultaneous infection of calves with BVDV and PI-3 virus or BVDV and IBR virus.

From the first experiment it seems that BVDV infection can be reactivated in calves by BHV-4 and IBR virus. Evidence of this is that BVDV, at least the cytopathic (CP) strain, was recovered from calves following superinfection. Moreover, following such superinfection the calves showed signs which could most likely be ascribed to the pathogenetic activity of BVDV. Superinfection, especially by IBR virus, created a more severe clinical response in calves that were initially infected with CP BVDV, than in those previously given the non-cytopathic (NCP) biotype of the virus. Simultaneous infection with PI-3 virus did not seem to modify to any significant extent the pathogenesis of the experimentally induced BVDV infection whereas a severe clinical response was observed in calves when simultaneous infection was made with BVDV and IBR virus.     

Long-term clinicopathological characteristics of alpacas naturally infected with bovine viral diarrhea virus type Ib

Background: Substantial bovine viral diarrhea virus (BVDV)‐related production losses in North American alpaca herds have been associated with BVDV type Ib infection. Objectives: To classify and differentiate the long‐term clinicopathological characteristics of BVDV type Ib infection of alpaca crias, after natural virus exposure. We hypothesized that persistently infected (PI) alpacas specifically demonstrate growth retardation, clinicopathological evidence of opportunistic infections, and early mortality. Animals: Thirty‐five crias naturally exposed to BVDV (18 acute, 3 chronic, 14 PIs), and 19 healthy cohort controls of 5 northeastern alpaca farms were prospectively evaluated over 2 years (September 2005–September 2008). Methods: Observational cohort‐control study. Results: Chronically (viremia >3 weeks) and PI crias demonstrated significantly lower birth weights, decreased growth rates, anemia, and monocytosis compared with control animals. Common clinical problems of PI alpacas included chronic wasting, diarrhea, and respiratory disease. Median survival of PI alpacas that died was 177 days (interquartile range, 555) with a case fatality rate of 50% within 6 months of life. Transplacental infection was confirmed in 82% (9/11) of pregnant females on 1 farm, resulting in the birth of 7 PI crias (7/10 deliveries; 1 animal was aborted). Mean gestation at the beginning and end of BVDV exposure was 64 and 114 days, respectively. Conclusions and Clinical Importance: Natural BVDV type 1b infection during early pregnancy resulted in a high incidence of PI offspring. Although PI alpacas may have distinct clinical characteristics, verification of persistent viremia in the absence of endogenous, neutralizing antibodies is essential to differentiate persistent from chronic infection.     

Prevalence of serum antibodies to bovine herpesvirus-1 and bovine viral diarrhea virus in beef cattle in Uruguay

Our objective was to determine the prevalence of serum antibodies to bovine herpesvirus-1 (BHV-1) and bovine viral diarrhea (BVD) virus in beef cattle in Uruguay. A random sample of 230 herds selected with probability proportional to population size based on the number of cattle was chosen from a list frame of all registered livestock farms as of June 1999. Sera from up to 10 heifers, cows and bulls (up to 30 sera total per herd) were collected on selected farms between March 2000 and March 2001 and evaluated by means of enzyme-linked immunosorbent assays (ELISAs). Overall, 6358 serum samples were evaluated. We also collected data on previous diagnosis of BHV-1 or BVD infections and on the use of vaccines against these agents.

The estimated prevalence of exposure to BHV-1 and BVD at the herd level for the Uruguayan beef population was 99% and 100%, respectively. Approximately 37% of beef cattle in Uruguay have been exposed to BHV-1 and 69% to BVD virus. Only 3% of beef herds in Uruguay regularly (typically, annually) use vaccines against either of these agents.     

Economic risk analysis model for bovine viral diarrhea virus biosecurity in cow-calf herds

A stochastic model was designed to calculate the cost-effectiveness of biosecurity strategies for bovine viral diarrhea virus (BVDV) in cow-calf herds. Possible sources of BVDV introduction considered were imported animals, including the calves of pregnant imports, and fenceline contact with infected herds, including stocker cattle raised in adjacent pastures. Spread of BVDV through the herd was modeled with a stochastic SIR model. Financial consequences of BVDV, including lost income, treatment costs, and the cost of biosecurity strategies, were calculated for 10 years, based on the risks of a herd with a user-defined import profile. Results indicate that importing pregnant animals and stockers increased the financial risk of BVDV. Strategic testing in combination with vaccination most decreased the risk of high-cost outbreaks in most herds. The choice of a biosecurity strategy was specific to the risks of a particular herd.     

Evaluation of bovine viral diarrhea virus control using a mathematical model of infection dynamics

A mathematical model for infection with bovine viral diarrhea virus (BVDV) was created comprising a series of coupled differential equations. The model architecture is a development of the traditional model framework using susceptible, infectious and removed animals (the SIR model). The model predicts 1.2% persistent infection (within the range of field estimates) and is fairly insensitive to alterations of structure or parameter values. This model allows us to draw important conclusions regarding the control of BVD, particularly with respect to the importance of persistently infected (PI) animals in maintaining BVD as an endemic entity in the herd. Herds without PI animals are likely to experience episodic reproductive losses at intervals of two to three years, unlike herds with PI animals which will not see such marked episodic manifestations of infection. Instead, these herds will experience an initial peak of disease which will settle to low-level chronic reproductive losses. The model indicates that vaccine coverage for herd immunity (to avoid episodic manifestations of disease) need be only 57% without PI animals, although 97% coverage is required when PI animals are present. Analysis of model behavior suggests, a program of detection and removal of PI animals may enhance the effectiveness of a vaccine program provided these animals are in the herd for 10 days or less. The best results would be seen with PI animals in the herd for 5 or fewer days.     

Reactivity and prevalence of neutralizing antibodies against Japanese strains of bovine viral diarrhea virus subgenotypes

Bovine viral diarrhea virus (BVDV) field isolates show genetic and antigenic diversity. At least 14 subgenotypes of BVDV-1 and 4 of BVDV-2 have been identified in Artiodactyla worldwide. Of these, 6 subgenotypes of BVDV-1 and 1 of BVDV-2 have been isolated in Japan. Previously, we reported that each subgenotype virus expresses different antigenic characteristics. Here we investigated the reactivity of neutralizing antibodies against representative strains of Japanese BVDV subgenotypes using sera from 266 beef cattle to estimate the prevalence of this epidemic virus among cattle in Japan. Antibody titers at concentrations at least 4-fold higher than antibodies against other subgenotype viruses were considered subgenotype specific. Subgenotype-specific antibodies were detected from 117 (80.7%) of 145 sera samples (69.7% against BVDV-1a, 1.4% against BVDV-1b, 8.3% against BVDV-1c, and 1.4% against BVDV-2a). The results suggest that neutralization tests are useful in estimating currently epidemic subgenotypes of BVDV in the field.     

Outbreak of acute bovine viral diarrhea in Brazilian beef cattle: clinicopathological findings and molecular characterization of a wild-type BVDV strain subtype 1b

When first described in 1946, bovine viral diarrhea (BVD) was characterized as an acute transmissible disease associated with severe leucopenia, high fever, depression, diarrhea, gastrointestinal erosions, and hemorrhages. Recently the severe acute form has been related only to some hypervirulent BVDV-2 strains. This article reports the detection of BVDV-1b associated with an acute and fatal outbreak of BVD in a Brazilian beef cattle herd. Depression, anorexia, watery diarrhea, sialorrhea, and weakness were observed in six steers. One of these animals was evaluated for laboratorial, clinical, and pathological alterations. Laboratory findings were non-specific; clinically, the animal was weak, with dehydration and erosive oral lesions. Pathological alterations were predominant at the tongue, esophagus, and rumen. A RT-PCR assay using primers to partially amplify the 5′ untranslated region (5′UTR) of the BVDV genome was performed and identified BVDV in all clinical samples analyzed. Phylogenetic analysis of BVDV derived from lymph node revealed that this strain was clustered within the BVDV subtype 1b. This differentiating was only possible to be performed by molecular characterization since both clinical presentation and pathologic findings were similar to BVDV-2 infection.     

牛病毒性腹泻病毒感染对猪瘟免疫的影响

猪瘟病毒（CSFV）与同属的牛病毒性腹泻病病毒（BVDV）同源性较高,抗原性上有交叉。本次调查对368份猪瘟免疫猪血清样本进行BVDV抗原检测,其中7份呈阳性,阳性率1.90%。对7份BVDV阳性血清采用ELISA和IHA两种方法检测猪瘟（CSFV）抗体水平,抗体合格率偏低,两者的结果符合率为71%。研究表明：BVDV在一定程度上干扰了猪瘟疫苗的免疫效果,影响抗体水平。     

Associations between health and productivity in cow-calf beef herds and persistent infection with bovine viral diarrhea virus, antibodies against bovine viral diarrhea virus, or antibodies against infectious bovine rhinotracheitis virus in calves

OBJECTIVE: To measure associations between health and productivity in cow-calf beef herds and persistent infection with bovine viral diarrhea virus (BVDV), antibodies against BVDV, or antibodies against infectious bovine rhinotracheitis (IBR) virus in calves. ANIMALS: 1,782 calves from 61 beef herds. PROCEDURES: Calf serum samples were analyzed at weaning for antibodies against type 1 and type 2 BVDV and IBR virus. Skin biopsy specimens from 5,704 weaned calves were tested immunohistochemically to identify persistently infected (PI) calves. Herd production records and individual calf treatment and weaning weight records were collected. RESULTS: There was no association between the proportion of calves with antibodies against BVDV or IBR virus and herd prevalence of abortion, stillbirth, calf death, or nonpregnancy. Calf death risk was higher in herds in which a PI calf was detected, and PI calves were more likely to be treated and typically weighed substantially less than herdmates at weaning. Calves with high antibody titers suggesting exposure to BVDV typically weighed less than calves that had no evidence of exposure. CONCLUSIONS AND CLINICAL RELEVANCE: BVDV infection, as indicated by the presence of PI calves and serologic evidence of infection in weaned calves, appeared to have the most substantial effect on productivity because of higher calf death risk and treatment risk and lower calf weaning weight.     

Serological relationships among subgroups in bovine viral diarrhea virus genotype 1 (BVDV-1)

Bovine viral diarrhea virus (BVDV) has various economic impacts associated with diarrhea, poor performance, an increase in the frequency of other infections and lethal outcomes. Both genotypes, namely BVDV-1 and BVDV-2, as well as different subgroups within these genotypes have been reported worldwide. Understanding the serological differences among the BVDV subgroups is important for disease epidemiology and prevention as well as vaccination programs. The aim of this study was to determine the serological relatedness among the subgroups in BVDV-1. For that purpose, sheep hyperimmune sera were collected against representative strains from 6 of the subgroups of BVDV-1 (BVDV-1a, -1b, -1d, -1f, -1h and -1l). The serum samples that gave the peak antibody titer to the homologous strains were used to perform cross neutralization assays. The highest homologous antibody titer (1:5160) was obtained against BVDV-1h. Regarding the cross neutralizing (heterologous) antibodies, the lowest titer (1:20) was produced by the BVDV-1f antiserum against the BVDV-1a and BVDV1-b viruses. The highest cross neutralizing titer (1:2580) achieved by the BVDV-1h antiserum was against the BVDV-1b strain. The cross neutralization results indicated particular serological differences between the recently described subgroup (BVDV-1l) and BVDV-1a/-1b, which are widely used in commercial vaccines. Considering the cross neutralization titers, it is concluded that selected BVDV-1l and BVDV-1h strains can be used for the development of diagnostic and control tools.     

二重RT-PCR同时检测VSV与BVDV核酸

水泡性口炎病毒(VSV)与牛病毒性腹泻病毒(BVDV)具有相近的传播途径与类似的检测方法，本文参照文献报道的基因序列，设计合成了两对能分别扩增VSV(202bp)、BVDV(341bp)基因片段的引物，并对PCR扩增条件进行优化，建立了二重RT-PCR方法，可同时检测VSV与BVDV病毒核酸。VSV产物经测序显示与报道的核酸序列同源性为88．6％。二重RT-PCR同时检测VSV与BVDV经济、快速、敏感、特异，可用于实验研究和流行病学调查。     

Survey on vertical infection of bovine viral diarrhea virus from fetal bovine sera in the field

Bovine viral diarrhea virus (BVDV) isolation and antibody survey were performed using 2,758 fetal bovine sera (FBS) collected from slaughterhouses in New Zealand, Australia and the Dominican Republic, and then sent to Japan to manufacture commercial serum for cell culture use. FBS in the Dominican Republic were pooled for each several individuals, and those collected in other countries were separated according to each individual and subjected to the tests. BVDV was isolated from 25 (0.91%) FBS, and the BVDV antibody was detected in 44 (1.60%) FBS. The survey on 139 sets of paired sera of a dam and her fetus revealed that neither the BVDV antibody nor BVDV was detected in all FBS from BVDV antibody-positive dams.     

Response of proinflammatory and anti-inflammatory cytokines in calves with subclinical bovine viral diarrhea challenged with bovine herpesvirus-1

The aim of this work was to investigate the susceptibility of calves infected with bovine viral diarrhea virus (BVDV) against secondary infections. For this purpose, the profile of cytokines implicated in the immune response of calves experimentally infected with a non-cytopathic strain of BVDV type-1 and challenged with bovine herpesvirus 1.1 (BHV-1.1) was evaluated in comparison with healthy animals challenged only with BHV-1.1. The immune response was measured by serum concentrations of cytokines (IL-1β, TNFα, IFNγ, IL-12, IL-4 and IL-10), acute phase proteins (haptoglobin, serum amyloid A and fibrinogen) and BVDV and BHV-1.1 specific antibodies. BVDV-infected calves displayed a great secretion of TNFα and reduced production of IL-10 following BHV-1 infection, leading to an exacerbation of the inflammatory response and to the development of more intense clinical symptoms and lesions than those observed in healthy animals BHV-1-inoculated. A Th1 immune response, based on IFNγ production and on the absence of significant changes in IL-4 production, was observed in both groups of BHV-1-infected calves. However, whereas the animals inoculated only with BHV-1 presented an IFNγ response from the start of the study and high expression of IL-12, the BVDV-infected calves showed a delay in the IFNγ production and low levels of IL-12. This alteration in the kinetic and magnitude of these cytokines, involved in cytotoxic mechanisms responsible for limiting the spread of secondary pathogens, facilitated the dissemination of BHV-1.1 in BVDV-infected calves.     

牛病毒性腹泻病毒基因组结构与蛋白功能研究进展

牛病毒性腹泻病毒为黄病毒科(Flaviviridae)瘟病毒属(Pestivirus)的代表种,这个属的成员中还包括羊边界病毒(BDV)和猪瘟病毒(CSFV)。病毒基因组为单股正链RNA。论文就牛病毒性腹泻病毒已定位的4种结构蛋白、8种非结构蛋白以及3′和5′非翻译区的基因结构特征及其编码蛋白的合成与功能研究进行了综述,为牛病毒性腹泻的防控和疫苗研制提供参考。     

In vitro and in vivo immune responses in neonatally thymectomized holstein-friesian calves exposed to bovine viral diarrhea virus

Neonatally thymectomized and normal Holstein-Friesian calves were exposed to bovine viral diarrhea virus and challenged 22 days later. Baseline values in non-specific mitogen induced lymphocyte blastogenesis and serologic responses to tetanus toxoid and Brucella abortus strain 19 were established in neonatally thymectomized and normal calves.Neither viral recovery nor protective antibody production followed the very low level primary exposure to bovine viral diarrhea virus. The expected clinical response to an appropriate challenge inoculum did not occur, however, suggesting an immune response to bovine viral diarrhea virus had been initiated by the primary exposure. Five of eight calves developed protective serum levels of bovine viral diarrhea antibody. This may represent an example of immunologic priming. Exposure to low levels of bovine viral diarrhea virus also has potential implications in the pathogenesis of chronic bovine viral diarrhea wherein low level exposure may interfere with the development of protective levels of bovine viral diarrhea antibody as was observed in three calves.Circulating lymphocyte concentrations and results of non-specific mitogen stimulation of lymphocytes revealed a reduced phytohemagglutinin response in conjunction with a slightly increased response to bacterial lipopolysaccharide and pokeweed mitogen in the presence of moderate lymphopenia. The capacity of lymphocytes to respond to phytohemagglutinin was unchanged but an increased total response, as occurred in control thymectomized and intact calves, did not occur.The response to tetanus toxoid, a thymus-independent antigen, was increased following exposure to bovine viral diarrhea virus, perhaps reflecting an alteration in thymic-independent regulation. The lack of a differential response to Brucella abortus strain 19 implied competence in thymus-dependent helper cells.