Persistent Bovine Viral Diarrhea Virus Infection Research Articles

Effect of calf age on bovine viral diarrhea virus tests.

Bovine viral diarrhea virus (BVDV) causes significant economic loss in cattle. Detection of persistently infected (PI) animals is an important control measure, but persistence of maternal antibodies may result in false-negative test results. We assessed the sensitivity and specificity of 2 antigen ELISAs (Idexx BVDV Ag/Serum Plus and BVDV PI X2) and a reverse-transcription real-time PCR (RT-rtPCR; Idexx RealPCR BVDV) assay for detecting PI calves. Ear notch samples were collected from 1,030 calves ~3, 10, 24, and 38 d old (days 3, 10, 24, and 38). All day 38 samples were tested using 2 antigen ELISAs and RT-rtPCR, and any calf that tested positive by any of these tests was blood sampled at ~100 d old (day 100) for antigen and antibody testing by ELISA; samples collected on days 3, 10, and 24 were tested using the antigen ELISAs and PCR. Calves were defined as PI if they were test-positive on day 38 by either ELISA or PCR and were antigen-positive on day 100. Twenty-six calves were PCR BVDV test-positive and one was BVDV PI X2 ELISA-positive at day 38. Five calves were defined as PI, and all tested positive by ELISAs and RT-PCR assay on days 3, 10, and 24. The sensitivity and specificity were 100% for both antigen ELISAs and 96.7% and 100%, respectively, by RT-rtPCR. Test results were not affected by calf age, suggesting that testing for PI calves can be undertaken at any age.

Prevalence of bovine abortion, calf mortality, and bovine viral diarrhea virus (BVDV) persistently infected calves among pastoral, peri-urban, and mixed-crop livestock farms in central and Northwest Ethiopia

BackgroundBovine Viral Diarrhea virus (BVDV) is one of important diseases of cattle worldwide causing economic losses to the cattle industry primarily due to increased premature culling and decreased reproductive performance. The virus can cross the placenta during early pregnancy and result in the birth of persistently infected (PI) calves that are efficient transmitters of BVDV and serving as the primary reservoirs for BVDV. Relatively few studies have focused on understanding BVDV seroprevalence, virus detection, genotyping and its distribution in Africa. Most BVDV research in Ethiopia has involved serologic surveys in adult cattle, rather than the identification of PI calves, despite their role in viral shedding and recurring infections. A cross-sectional study was undertaken in three different livestock production systems of Ethiopia with the objective to estimate the prevalence of bovine abortion, calf mortality, and BVDV persistently infected calves.ResultsEar notch samples (882) collected from calves in 349 households were tested for BVDV antigen using antigen capture enzyme-linked immunosorbent assay (ACE). All samples tested were negative for BVDV antigen. The overall animal level crude abortion and calf mortality prevalence were 4.0% (95% CI: 2.9–5.2) and 9.2% (95% CI: 7.7–11.0) respectively. The lower BVDV PI prevalence may be due to a lower effective contact rate between cattle reared in small-scale extensive production systems in Ethiopia.ConclusionsThis is the first report of BVDV Ag test in Ethiopia and no PI was detected in calves in the study areas. Since BVDV is a disease of great economic importance, this study finding must be interpreted with care since absence of evidence is not evidence of absence and even a single BVDV infected animal can serve as source of infection and contribute to the persistent spread of the virus. Greater attention needs to be given to screening for PI animals through testing large number of animals and culling positive animals. Hence, future research should focus on regions and production systems with high BVDV seroprevalence followed by antigen ELISA or BVDV real-time PCR to detect persistently infected and acutely viremic animals.

Risk factors associated with the within-farm transmission of bovine viral diarrhea virus and the incidence of persistently infected cattle on dairy farms from Ibaraki prefecture of Japan

For understanding the factors affecting bovine viral diarrhea virus (BVDV) transmission, this study investigated the distribution of BVDV and the epidemiological features of persistently infected (PI) cattle in Ibaraki Prefecture of Japan, and identified farm-level risk factors associated with BVDV infection, with a focus on within-farm transmission and PI animal detection.Among all 377 dairy farms, forty-four PI cattle were identified on 22 farms. Thirty-eight and six PI cattle were born on their current farms or purchased, respectively. Twenty-six PI cattle were born from pregnancies on their current farms, seven from pregnancies in summer pastures, and eight from pregnancies on other farms. The within-farm seroprevalence on farms with PI animals was significantly higher than that on farms without PI cattle.Of 333 farms holding homebred cattle without movement records, antibody-positivity in homebred cattle was observed on 194 farms; these cattle were likely infected by within-farm transmission. Herd size, summer pasturing, and BVDV infection status of the nearest dairy farm were risk factors associated with within-farm transmission. Likewise, herd size, summer pasturing, and the proportion of purchased cattle were related to PI animal occurrence.This study shows the risk of within-farm transmission and occurrence of PI animals after the introduction of BVDV via purchasing and summer pasturing, and illustrates the significant role of PI cattle in circulating BVDV. More effective measures for screening BVDV infection and PI animals, including intensive tests targeting moved cattle and newborn calves, and bulk milk surveillance, are required to control the spread of BVDV in Japan.

Prevalence and genetic diversity of bovine viral diarrhea virus in dairy herds of China

To determine the nationwide prevalence and genetic diversity of bovine viral diarrhea virus (BVDV) in China, 92 dairy farms with more than 500 animals in 19 provinces of China were surveyed in 2017. At each farm, ear notch samples from calves less than six months old and bulk tank milk (BTM) samples were collected. A total of 901 ear notch samples and 329 BTM samples from 183 tanks were sampled. A total of 20 (20/901, 2.22 %) ear notch samples from 10 (10/92, 10.86 %) farms tested positive for BVDV by IDEXX Antigen Point-of-Care (POC) Test kit and real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR). In addition, 80 of 183 (80/183, 43.7 %) BTM samples from 43 (43/92, 46.7 %) farms were identified as positive by qRT-PCR. The RNA of positive and suspect samples identified by qRT-PCR was subjected to 5′- untranslated region (UTR) amplification by nested RT-PCR and then sequenced. A total of 119 sequences were obtained and phylogenetic analysis of these 5′-UTR sequences revealed the presence of eight different subgenotypes of BVDV-1 including 1a (n = 37, 31.09 %), 1b (n = 5, 4.20 %), 1c (n = 34, 28.57 %), 1d (n = 2, 1.68 %), 1m (n = 25, 21.01 %), 1q (n = 6, 5.04 %), and two unknown subgenotypes which were tentatively typed as “BVDV-1v” (n = 8, 6.72 %) and “BVDV-1w” (n = 2, 1.68 %), respectively. BVDV-1a, 1c, and 1m were the dominant strains, collectively accounting for 80.67 % (96/119) of all sequences. Phylogenetic analysis based on selected N-terminal autoprotease (Npro) sequences confirmed the classification of the 5′-UTR sequences. In conclusion, the prevalence of BVDV persistent infection in dairy cattle was high and genetic diversity was high and increasing, revealing a serious threat to the health of cattle in China and highlighting the need for BVDV control.

Discovery of Novel Bovine Viral Diarrhea Inhibitors Using Structure-Based Virtual Screening on the Envelope Protein E2.

Bovine viral diarrhea virus (BVDV) is a member of the genus Pestivirus within the family Flaviviridae. BVDV causes both acute and persistent infections in cattle, leading to substantial financial losses to the livestock industry each year. The global prevalence of persistent BVDV infection and the lack of a highly effective antiviral therapy have spurred intensive efforts to discover and develop novel anti-BVDV therapies in the pharmaceutical industry. Antiviral targeting of virus envelope proteins is an effective strategy for therapeutic intervention of viral infections. We performed prospective small-molecule high-throughput docking to identify molecules that likely bind to the region delimited by domains I and II of the envelope protein E2 of BVDV. Several structurally different compounds were purchased or synthesized, and assayed for antiviral activity against BVDV. Five of the selected compounds were active displaying IC50 values in the low- to mid-micromolar range. For these compounds, their possible binding determinants were characterized by molecular dynamics simulations. A common pattern of interactions between active molecules and aminoacid residues in the binding site in E2 was observed. These findings could offer a better understanding of the interaction of BVDV E2 with these inhibitors, as well as benefit the discovery of novel and more potent BVDV antivirals.

Prevalence of bovine viral diarrhea virus (BVDV) persistently infected calves in auction markets from the southeastern United States; association between body weight and BVDV-positive diagnosis

Bovine viral diarrhea virus (BVDV) is a ubiquitous infectious agent affecting cattle worldwide. Animals that are born persistently infected (PI) with BVDV are considered the primary viral reservoirs in cattle herds and are capable of shedding copious amounts of virus into the environment. The objectives of this study were to determine the prevalence of BVDV PI among stocker calves in the southeastern United States and evaluate whether lighter BW cattle would have a greater prevalence of BVDV persistent infection than heavier BW cattle. Stocker calves from auction markets in Alabama, Florida, Georgia, Mississippi, and Tennessee were sampled from March to December 2005. Following purchase, they were transported to a central holding facility where the calves were processed, sorted, and assembled into truckload lots based on their average BW. Skin biopsies (ear notches) were collected in zinc buffered formalin for the detection of BVDV persistent infection using immunohistochemistry. Twenty-four BVDV-positive calves were detected in a sampling of 7,544 calves. The overall BVDV PI prevalence in stocker calves sampled was measured at 0.318%. This prevalence agreed closely with the BVDV PI prevalence reported previously in other regions of the United States. In this study, calves weighing less than 180 kg had greater BVDV PI prevalence with 2.78 times greater probability of being PI animals compared with calves over 180 kg.

Induction of interferon-gamma and downstream pathways during establishment of fetal persistent infection with bovine viral diarrhea virus

Development of transplacental infection depends on the ability of the virus to cross the placenta and replicate within the fetus while counteracting maternal and fetal immune responses. Unfortunately, little is known about this complex process. Non-cytopathic (ncp) strains of bovine viral diarrhea virus (BVDV), a pestivirus in the Flaviviridae family, cause persistent infection in early gestational fetuses (<150 days; persistently infected, PI), but are cleared by immunocompetent animals and late gestational fetuses (>150 days; transiently infected, TI). Evasion of innate immune response and development of immunotolerance to ncp BVDV have been suggested as possible mechanisms for the establishment of the persistent infection. Previously we have observed a robust temporal induction of interferon (IFN) type I (innate immune response) and upregulation of IFN stimulated genes (ISGs) in BVDV TI fetuses. Modest chronic upregulation of ISGs in PI fetuses and calves reflects a stimulated innate immune response during persistent BVDV infection. We hypothesized that establishing persistent fetal BVDV infection is also accompanied by the induction of IFN-gamma (IFN-γ). The aims of the present study were to determine IFN-γ concentration in blood and amniotic fluid from control, TI and PI fetuses during BVDV infection and analyze induction of the IFN-γ downstream pathways in fetal lymphoid tissues. Two experiments with in vivo BVDV infections were completed. In Experiment 1, pregnant heifers were infected with ncp BVDV type 2 on day 75 or 175 of gestation or kept naïve to generate PI, TI and control fetuses, respectively. Fetuses were collected by Cesarean section on day 190. In Experiment 2, fetuses were collected on days 82, 89, 97, 192 and 245 following infection of pregnant heifers on day 75 of gestation. The results were consistent with the hypothesis that ncp BVDV infection induces IFN-γ secretion during acute infection in both TI and PI fetuses and that lymphoid tissues such as spleen, liver and thymus, serve both as possible sources of IFN-γ and target organs for its effects. Notably, induction of IFN-γ coincides with a decrease in BVDV RNA concentrations in PI fetal blood and tissues. This is the first report indicating the possible presence of an adaptive immune response in persistent BVDV infections, which may be contributing to the observed reduction of viremia in PI fetuses.

Spontane bloedingen bij een pasgeboren kalf met persisterende BVDV1b-infectie

Een kalf vertoonde op zijn tweede levensdag huidbloedingen en werd doorverwezen naar de kliniekonder verdenking van boviene neonatale pancytopenie (BNP). Hematologisch onderzoek toonde extremetrombocytopenie, matige anemie, maar geen leukopenie aan. Een PCR-test op gehepariniseerd bloed waspositief voor het boviene virale diarreevirus (BVDV), net als bij twee BVDV-antigeen ELISA’s op bloeddie drie en tien weken later genomen werden. Niet-cytopathogeen BVDV-type 1b werd geïsoleerd uit hetbloed. Alhoewel het kalf herstelde van de bloedingen en gezond bleef, werd het wegens de persisterendeBVDV-infectie geëuthanaseerd op de leeftijd van elf weken. Op basis van de anamnese kon BNPuitgesloten worden uit de differentiaaldiagnose. Deze casus toont aan dat het bloedingssyndroom nietuitsluitend het gevolg is van besmetting met BVDV-type 2 en dat de klinische verschijnselen bij metBVDV1b besmette neonatale kalveren identiek kunnen zijn aan deze bij BNP.

Liver tolerance as a mechanism for the development of BVDV persistent infection

Bovine viral diarrhea virus (BVDV) is a member of the pestivirus group of the Flavivirus family that also includes hepatitis C virus. Infection of a pregnant cow with BVDV from 40 to 120 days of gestation may result in persistent infection (PI) of the fetus with BVDV. In pregnant cows, BVDV infects the cells of the placenta and crosses into fetal circulation. Persistently infected calves have been recognized as the major reservoir for BVDV; therefore, identification and removal of PI calves are the focus of BVDV eradication efforts. The objective of this study was to evaluate the association of the fetal liver and liver tolerance with the development of PI with BVDV.

Clinical and reproductive consequences of using BVDV-contaminated semen in artificial insemination in a beef herd in Argentina

The current report was prompted by an atypical outbreak of mucosal disease that occurred in a beef herd in the southwestern part of Buenos Aires Province, Argentina, where a total of 9/41 (21.9%) yearling bulls died. Blood samples from 73 bulls and 189 heifers were tested for evidence of persistent BVDV infection with Bovine Viral Diarrhea Virus (BVDV). Non-cytopathic BVDV was isolated from 7 (9.6%) 24- to 36-month-old bulls, and 3 (1.6%) 36-month-old heifers. Non-cytopathic BVDV was also detected in the seminal plasma of three of six persistently infected (PI) bulls. Furthermore, a 171bp genomic fragment of BVDV was consistently detected by nested RT-PCR in one of the two samples of the commercial semen used for artificial insemination, indicating that this semen could be a possible source of infection for the whole herd. To evaluate the possible reproductive consequences of PI heifers and bulls, ovaries and semen were obtained from PI cattle for in vitro assays. The in vitro fertilization of oocytes with semen from PI bulls was associated with decreased cleavage and embryo development rates. Additionally, non-cytopathic BVDV was isolated from the follicular fluid of PI heifers. Genetic typing revealed that all isolates BVDV from the present study had a high percentage of homology and that all of the fragments from the RT-PCR clearly fit with the BVDV 1b cluster. These findings confirm the negative impact that BVDV can have on the reproductive performance of cattle and the importance of applying the proper sanitary controls to minimize the risk of BVDV infection.

Combination of Reverse Transcription Real-Time Polymerase Chain Reaction and Antigen Capture Enzyme-Linked Immunosorbent Assay for the Detection of Animals Persistently Infected with Bovine Viral Diarrhea Virus

Bovine viral diarrhea virus (BVDV) is an economically important pathogen of cattle. A successful control program requires early detection and removal of persistently infected (PI) animals. The objective of the current study was to develop, validate, and apply a cost-effective testing scheme for the detection of BVDV PI animals in exposed herds. Pooled samples were screened by using a real-time reverse transcription polymerase chain reaction (real-time RT-PCR), and individual positives were identified with an antigen capture enzyme-linked immunosorbent assay (ACE). The detection limits of the optimized real-time RT-PCR were 10 and 100 RNA copies per reaction for BVDV-1 and BVDV-2, respectively. The semiquantitative results of real-time RT-PCR and ACE or real-time RT-PCR and immunohistochemistry were moderately correlated. The threshold cycle of real-time RT-PCR performed on pooled samples was significantly correlated with the pool size (R(2) = 0.993). The least-cost pool sizes were 50 at a prevalence of 0.25-0.5% and 25 at a prevalence of 0.75-2.0%. By using the combined real-time RT-PCR and ACE procedure, 111 of 27,932 samples (0.4%) tested positive for BVDV. At this prevalence, cost reduction associated with the application of real-time RT-PCR and ACE ranged from 61% to 94%, compared with testing individual samples by ACE, immunohistochemistry, or real-time RT-PCR. Real-time RT-PCR screening also indicated that 92.94% of PI animals were infected with BVDV-1, 3.53% with BVDV-2, and 3.53% with both BVDV-1 and BVDV-2. Analysis of the 5'-untranslated region of 22 isolates revealed the predominance of BVDV-1b followed by BVDV-2a.

Loci on Bos taurus chromosome 2 and Bos taurus chromosome 26 are linked with bovine respiratory disease and associated with persistent infection of bovine viral diarrhea virus1

The objective of this study was to identify loci linked with bovine respiratory disease (BRD) and subsequently to determine if these same loci were associated with bovine viral diarrhea virus persistent infection (BVD-PI) in affected calves or their dams. A genome-wide linkage study using 312 microsatellites was conducted to identify loci linked with BRD in a Brahman × Hereford sire half-sib family. Disease incidence was recorded from birth to slaughter by daily monitoring. Linkage was suggestive for a QTL on BTA2 (F = 7.31, P = 0.007) and BTA26 (F = 10.46, P = 0.001). Six and 7 markers were added and genotyped between 110 and 126 cM on BTA2 and between 42 and 72 cM on BTA26, respectively, in the intervals where linkage was found. These markers were used to reevaluate the Brahman × Hereford family and to evaluate 3 additional crossbred half-sib families. Linkage was found with BRD on BTA2 (F = 4.94, P < 0.01), with a peak at 110 cM, and on BTA26 (F = 4.03, P < 0.05), with peaks at 42 and 52 cM. The same markers were then tested for an association with BVD-PI in 1) BVD-PI calves compared with age-matched unaffected calves from the same herd or 2) dams with BVD-PI compared with age-matched unaffected calves. Sixty commercial beef cow-calf herds were tested for BVD-PI, and 79 calves from 8 ranches had BVD-PI. Four of 6 markers were associated (P = 4.8 × 10(-9) to P = 0.01) with BVD-PI on BTA2, and 4 of 7 markers were associated (P = 0.008 to P = 0.04) with BVD-PI on BTA26 when BVD-PI calves were compared with unaffected calves. The comparison of BVD-PI dams with unaffected calves detected associations with BVD-PI for all markers tested on BTA2 (P = 3 × 10(-9) to P = 0.005) and for 3 of 7 markers on BTA26 (P = 1.4 × 10(-6) to P = 0.006).

Evaluation of economic effects and the health and performance of the general cattle population after exposure to cattle persistently infected with bovine viral diarrhea virus in a starter feedlot

To evaluate economic effects and health and performance of the general cattle population after exposure to cattle persistently infected (PI) with bovine viral diarrhea virus (BVDV) in a feedlot. 21,743 high-risk calves from the southeastern United States. PI status was determined by use of an antigen-capture ELISA (ACE) and confirmed by use of a second ACE, reverse transcriptase-PCR assay of sera, immunohistochemical analysis, and virus isolation from sera. Groups with various amounts of exposure to BVDV PI cattle were used. After being placed in the feedlot, identified PI cattle were removed from 1 section, but PI cattle remained in another section of the feedlot. Exposure groups for cattle lots arriving without PI animals were determined by spatial association to cattle lots, with PI animals remaining or removed from the lot. 15,348 cattle maintained their exposure group. Performance outcomes improved slightly among the 5 exposure groups as the risk for exposure to BVDV PI cattle decreased. Health outcomes had an association with exposure risk that depended on the exposure group. Comparing cattle lots with direct exposure with those without direct exposure revealed significant improvements in all performance outcomes and in first relapse percentage and mortality percentage in the health outcomes. Economic analysis revealed that fatalities accounted for losses of $5.26/animal and performance losses were $88.26/animal. This study provided evidence that exposure of the general population of feedlot cattle to BVDV PI animals resulted in substantial costs attributable to negative effects on performance and increased fatalities.

Systemic Reactive Angioendotheliomatosis-like Syndrome in a Steer Presumed to be Persistently Infected with Bovine Viral Diarrhea Virus

Unusual proliferative intravascular lesions were seen in multiple organs of a 2-year-old Corriente steer presumed to be persistently infected with bovine viral diarrhea virus (BVDV), based on widespread immunohistochemical detection of BVDV antigen. Proliferations of spindle cells, which were immunohistochemically positive for von Willebrand factor-related antigen, partially-to-completely occluded vessel lumens and were supported by cells that were immunohistochemically positive for smooth muscle actin. Distribution and character of the intraluminal proliferations are strikingly similar to those described in feline systemic reactive angioendotheliomatosis, a rare entity of unknown cause. The presence of occasional intravascular thrombi suggests that the proliferative vasculopathy was associated with an underlying thrombotic process with immunohistochemical similarities to thrombotic thrombocytopenic purpura of humans. Death of the steer was due to hemorrhage from a castration wound, which may indicate thrombocytopenia or platelet dysfunction. The role of persistent BVDV infection in the formation of the intravascular lesions is unknown.

Persistent Bovine Viral Diarrhea virus Infection in Wild Cervids of Colorado

Bovine viral diarrhea virus (BVDV) is a significant viral pathogen of domestic cattle. Worldwide, there is evidence of BVDV exposure and infection in wild ungulates; however, the frequency and significance of such events are unknown. To determine the prevalence and distribution of Colorado deer, elk, and moose persistently infected (PI) with BVDV, a cross-sectional study was conducted using full-thickness ear tissue samples collected from animals presented to the Colorado Division of Wildlife for chronic wasting disease surveillance in the 2005-2006 hunting season. Tissue from 5,597 harvested animals (2,934 mule deer, 2,516 elk, 141 white-tailed deer, and 6 moose) was paraffin-embedded and stained for BVDV using immunohistochemistry. A single adult male mule deer had BVDV antigen in the skin; staining distribution was consistent with that seen in PI cattle. Skin and lymph node were also positive for viral RNA by polymerase chain reaction, and the virus was determined to be a type 1. The prevalence of BVDV PI cervids in Colorado is very low. However, the identification of a naturally infected adult PI animal in the wild suggests that the virus infects free-ranging populations. The source of the BVDV is unknown and is assumed to be spillover from cattle or maintenance within wildlife populations. Consideration of a potential wild animal reservoir is important in the design and implementation of BVDV management practices in cattle.

Cohabitation of pregnant white-tailed deer and cattle persistently infected with Bovine viral diarrhea virus results in persistently infected fawns

Economic losses due to infection with Bovine viral diarrhea virus (BVDV) have prompted introduction of organized control programs. These programs primarily focus on the removal of persistently infected (PI) animals, the main source of BVDV transmission. Recently, persistent BVDV infection was demonstrated experimentally in white-tailed deer, the most abundant wild ruminant in North America. Contact of cattle and white-tailed deer may result in interspecific BVDV transmission and birth of persistently infected offspring that could be a threat to control programs. The objective of this study was to assess the potential for interspecific BVDV transmission from persistently infected cattle cohabitated with pregnant white-tailed deer. Seven female and one male white-tailed deer were captured and bred in captivity. At approximately 50 days of gestation, two cattle persistently infected with BVDV 1 were cohabitated with the deer. In a pen of approximately 0.8 ha, both species shared food and water sources for a period of 60 days. Transmission of BVDV as indicated by seroconversion was demonstrated in all exposed adult deer. Of the seven pregnancies, four resulted in offspring that were infected with BVDV. Persistent infection was demonstrated in three singlet fawns by immunohistochemistry and ELISA on skin samples, PCR, and virus isolation procedures. Furthermore, two stillborn fetuses were apparently persistently infected. This is the first report of BVDV transmission from cattle to white-tailed deer using a model of natural challenge. Under appropriate circumstances, BVDV may efficiently cross the species barrier to cause transplacental infection and persistently infected offspring in a wildlife species.

Evaluation of Hunter-Harvested White-Tailed Deer for Evidence of Bovine Viral Diarrhea Virus Infection in Alabama

Bovine viral diarrhea virus (BVDV) is one of the most relevant pathogens affecting today's cattle industries. Although great strides have been made in understanding this virus in cattle, little is known about the role of wildlife in the epidemiology of BVDV. While persistently infected cattle are the most important reservoir, free-ranging ungulates may become infected with BVDV as demonstrated by serosurveys and experimental infections. Therefore, free-ranging wildlife may maintain BVDV as the result of an independent cycle and may serve as a reservoir for the virus. Systematic studies on prevalence of BVDV-specific antibodies or frequency of persistent BVDV infection in North American wildlife are sparse, and no information is available from the southeastern United States. The objective of this study was to evaluate blood and skin samples from hunter-harvested white-tailed deer (Odocoileus virginianus) for evidence of BVDV infection. Virus-neutralizing antibodies were detected in 2 of 165 serum samples. Skin biopsy immunohistochemistry (IHC) was performed on samples from 406 deer using a BVDV-specific monoclonal antibody (MAb) (15c5), and BVDV antigen was detected in one sample. A similar IHC staining pattern was obtained using a second BVDV MAb (3.12F1). Viral antigen distribution in the skin sample of this deer resembled that found in persistently infected cattle and in a previously described persistently infected white-tailed deer; thus, the deer was presumed to be persistently infected. Evidence of BVDV infection in free-ranging white-tailed deer should encourage further systematic investigation of the prevalence of BVDV in wildlife.

Prevalence of Neospora caninum and persistent infection with bovine viral diarrhea virus in dairy-breed steers in a feedlot

To determine the prevalence and effect of Neospora caninum infection and persistent infection (PI) with bovine viral diarrhea virus (BVDV) on weight gain, morbidity, and mortality rate in dairy-breed steer calves located on a feedlot in California. Prospective cohort observational study. 900 dairy-breed steer calves in 2 pens. The 3- to 4-month-old calves were evaluated for serum antibodies against N caninum and infection with BVDV at entry to the feedlot. Five months later, sera were again analyzed for anti-N caninum antibodies; calves that were determined to have BVDV infection initially were retested to evaluate PI status. Average daily gain, morbidity, and deaths were recorded for all calves. Among 900 calves, prevalence of N caninum infection was 16.7% (95% confidence interval, 14.3% to 19.3%); prevalence of BVDV-associated PI was 0.2% (95% confidence interval, 0.03% to 0.9%). Morbidity rate and time to first illness were not significantly different between calves that were seropositive or seronegative for N caninum. At the second sample collection, weight and average daily gain of calves that were seropositive for N caninum was less than that of seronegative steers in 1 pen, whereas these measures did not differ between groups in the other pen. Statistical power was insufficient to evaluate the effect of BVDV PI on any outcome measurement. Although N caninum serostatus had no significant effect on morbidity rate, some seropositive calves had reduced growth, compared with seronegative calves, 5 months after entry to the feedlot.

Diagnostic efficacy of a reverse transcriptase–polymerase chain reaction assay to screen cattle for persistent bovine viral diarrhea virus infection

To evaluate diagnostic efficacy of a reverse transcriptase-PCR assay performed on pooled supernatant from fresh tissue samples to screen cattle for persistent infection with bovine viral diarrhea virus (BVDV). Cross-sectional study. 174 pooled supernatant samples representing 12,528 animals between 1 and 12 months old. The supernatant was collected from fresh tissue samples suspended in phosphate-buffered saline solution that had been submitted for testing for BVDV infection. Supernatant samples were pooled, with pool size limited to < or = 100 samples, and assayed with a reverse transcriptase-PCR assay for BVDV. Results of the PCR assay were compared with results of an antigen-capture ELISA performed on individual tissue samples. Results of the PCR assay were positive for 27 of the 174 pooled samples (mean pool size, 72 samples). For 23 of these 27 pooled samples, results of the ELISA were positive for 1 or more of the individual tissue samples represented in the pooled sample, whereas for 4 of these pooled samples, results of the ELISA were negative for all individual tissue samples represented in the pooled sample. Results of the ELISA were negative for all individual tissue samples represented in the 147 pooled samples with negative PCR assay results. Results suggested that the reverse transcriptase-PCR assay can be used to screen cattle for persistent BVDV infection, with calculated sensitivity of 100% (95% confidence interval, 85.2% to 100%) and calculated specificity of 97.5% (95% confidence interval, 93.4% to 99.3%).

Investigation of the Role of Bovine Viral Diarrhea Virus (BVDV) in Undifferentiated Fever of Feedlot Cattle

The undifferentiated fever (UF)/bovine respiratory disease (BRD) complex continues to be the single most important infectious disease entity in beef feedlot production. Current management practices have focused on successfully managing this disease complex through the use of prophylactic and therapeutic antimicrobial strategies, as well as vaccination programs targeting common viral and bacterial etiologic agents of feedlot UF/BRD described in the veterinary literature. In spite of these preventive and control strategies, there are substantial amounts of concrete and circumstantial epidemiologic, pathologic, serologic, and immunologic evidence that BVDV infection continues to play an important role in UF/BRD in commercial feedlot production, even though BVDV vaccination programs are in use.&#x0D; The purpose of the project reported herein was to improve our understanding of the role that BVDV plays in the pathogenesis of pen-level UF/BRD. The specific objectives of this study were: to describe the frequency and character (Type I or Type II) of BVDV infections both persistent infection (PI) and acute infection (AI)) at feedlot arrival and at the time of initial UF diagnosis; to investigate the effects of BVDV PI animals on pen-level animal health and feedlot performance; to investigate the effect of BVDV viremia on subsequent animal health outcome; and to describe the frequency of BVDV identification in postmortem tissue samples using immunohistochemistry.