Reverse transcription-polymerase chain reaction on pooled samples to detect bovine viral diarrhea virus by using fresh ear-notch-sample supernatants

Comparative Analysis of the Prevalence of Bovine Viral Diarrhea Virus in Cattle Populations Based on Detection Methods: A Systematic Review and Meta-Analysis

Infectious diseases of cattle, including bovine viral diarrhea (BVD), pose a significant health threat to the global livestock industry. This study aimed to investigate the prevalence and risk factors associated with bovine viral diarrhea virus (BVDV) infections in cattle populations through a systematic review and meta-analysis. PubMed, Web of Science, and Scopus were systematically searched for relevant articles reporting the prevalence of and associated risk factors in studies published between 1 January 2000 and 3 February 2023. From a total of 5111 studies screened, 318 studies were included in the final analysis. BVDV prevalence in cattle populations was estimated using various detection methods. The analysis detected heterogeneity in prevalence, attributed to detection techniques and associated risk factors. Antibody detection methods exhibited a higher prevalence of 0.43, reflecting the cumulative effect of detecting both active and past infections. Antigen detection methods showed a prevalence of 0.05, which was lower than antibody methods. A prevalence of 0.08 was observed using nucleic acid detection methods. The health status of the examined cattle significantly influenced the prevalence of BVDV. Cattle with bovine respiratory disease complex (BRDC) exhibited higher antibody (prevalence of 0.67) and antigen (prevalence 0.23) levels compared to cattle with reproductive problems (prevalence 0.13) or diarrhea (prevalence 0.01). Nucleic acid detection methods demonstrated consistent rates across different health conditions. Age of cattle influenced prevalence, with higher rates in adults compared to calves. Risk factors related to breeding and reproduction, such as natural or extensive breeding and a history of abortion, were associated with increased prevalence. Coinfections with pathogens like bovine herpesvirus-1 or Neospora caninum were linked to higher BVDV prevalence. Management practices, such as commingling, introducing new cattle, and direct contact with neighboring farms, also influenced prevalence. Herd attributes, including larger herd size, and the presence of persistently infected cattle, were associated with higher prevalence. These findings indicated the importance of detection methods and risk factors in BVDV epidemiological studies.

Utilizing blood filter paper and ear punch samples for the detection of rabbit hemorrhagic disease virus 2 by RT-rtPCR

Rabbit hemorrhagic disease virus 2 (RHDV2), a virulent and contagious viral pathogen that affects wild and domestic lagomorph populations, was identified in Wyoming, USA in December 2020. A surveillance program was developed involving full-carcass submission and liver analysis, although carcass quality as a result of predation and decomposition impeded analysis. To increase the number of submissions and provide flexibility to field staff, we evaluated 2 sample types: 77 dried blood on filter paper samples, 66 ear punch samples. At initial sampling, test specificity and sensitivity of the RT-rtPCR utilizing dried blood on filter paper and ear punch samples were both 100% compared to liver. Filter paper results were consistent over time; sensitivity stayed >96% through weeks 2, 4, and 6, with a maximum mean difference of 6.0 Ct from baseline liver Ct values (95% CI: 5.0-7.3) at 6 wk. Test sensitivity of the ear punch sample at 1, 3, 5, and 7 wk post-sampling remained at 100%, with a maximum mean difference of 5.6 Ct from baseline liver Ct values (95% CI: 4.3-6.9) at 5 wk. Filter paper and ear punch samples were suitable alternatives to liver for RHDV2 surveillance in wild lagomorph populations. Alternative sampling options provide more flexibility to surveillance programs, increase testable submissions, and decrease exposure of field personnel to zoonotic disease agents.

First detection of emerging HoBi-like Pestivirus (BVD-3) among some persistently infected dairy cattle herds in Egypt

Bovine viral diarrhoea virus (BVDV) is a serious veterinary health concern worldwide. We conducted this study to determine the prevalence of persistent infections (PI) and identify the current strain among some dairy cattle herds in Egypt. A total of 240 serum samples were collected from six Egyptian provinces. Between 2019 and 2020, samples were tested by Enzyme linked immunosorbent assay (ELISA) for detection of PI animals, and then molecular characterization was performed. Six calves were found PI with a prevalence of 2.5% (6/240). Using molecular characterization, HoBi-like Pestivirus (BVD-3) was successfully identified in Egypt for the first time. Based on the BVD-3 reference strains on Genbank, the detected strains had an identity ranging from 98.8 to 99.6%. Partial nucleotide sequence of the 5'UTR gene for six tested samples was submitted to Genbank with accessions: OM324396, OM324397, OM324398, OM324399, OM3243100, and OM3243101.

Saving Resources: SARS-CoV-2 Diagnostics by Real-Time RT-PCR Using Reduced Reaction Volumes

Since the beginning of 2020, the betacoronavirus SARS-CoV-2 is causing a global pandemic of an acute respiratory disease termed COVID-19. The diagnostics of the novel disease is primarily based on direct virus detection by RT-PCR; however, the availability of test kits may become a major bottleneck, when millions of tests are performed per week. To increase the flexibility of SARS-CoV-2 diagnostics, three real-time RT-PCR assays listed on the homepage of the World Health Organization were selected and investigated regarding their compatibility with three different RT-PCR kits. Furthermore, the reaction volume of the PCR chemistry was reduced up to half of the original protocol to make the individual reactions more cost- and resource-effective. When testing dilution series of culture-grown virus, nearly identical quantification cycle values (Cq) were obtained for all RT-PCR assay/chemistry combinations. Regarding the SARS-CoV-2 detection in clinical samples, agreeing results were obtained for all combinations for virus negative specimens and swabs containing high to medium viral genome loads. In cases of very low SARS-CoV-2 genome loads (Cq > 36), inconsistent results were observed, with some test runs scoring negative and some positive. However, no preference of a specific target within the viral genome (E, RdRp, or N) or of a certain chemistry was seen. In summary, a reduction of the reaction volume and the type of PCR chemistry did not influence the PCR sensitivity.

Use of pooled serum samples to assess herd disease status using commercially available ELISAs

Pooled samples are used in veterinary and human medicine as a cost-effective approach to monitor disease prevalence. Nonetheless, there is limited information on the effect of pooling on test performance, and research is required to determine the appropriate number of samples which can be pooled. Therefore, this study aimed to evaluate the use of pooled serum samples as a herd-level surveillance tool for infectious production-limiting diseases: bovine viral diarrhoea (BVD), infectious bovine rhinotracheitis (IBR), enzootic bovine leukosis (EBL) and Neospora caninum (NC), by investigating the maximum number of samples one can pool to identify one positive animal, using commercial antibody-detection ELISAs. Four positive field standards (PFS), one for each disease, were prepared by pooling highly positive herd-level samples diagnosed using commercially available ELISA tests. These PFS were used to simulate 18 pooled samples ranging from undiluted PFS to a dilution representing 1 positive in 1,000 animals using phosphate-buffered saline as diluent. A 1:10 dilution of the PFS resulted in positive results for IBR, BVD and EBL. Moreover, for IBR and BVD, results were still positive at 1:100 and 1:30 dilutions, respectively. However, for NC, a lower dilution (8:10) was required for a seropositive result. This study indicates that, at herd-level, the use of pooled serum is a useful strategy for monitoring infectious diseases (BVD, IBR and EBL) but not NC, using readily available diagnostic assays.

The Principles of the Voluntary Programme for the Control and Elimination of Bovine Viral Diarrhoea Virus (BVDV) From Infected Herds in Slovenia

In Slovenia, the control of bovine viral diarrhoea virus (BVDV) infections started in 1994. Since 2014, a voluntary programme has been running according to the national rules that prescribe the conditions for recognising, acquiring, and maintaining a BVDV-free status for an individual herd. The principle is based on periodical laboratory testing and preventive measures that need to be strictly implemented in a herd. Between 2014 and 2020, a total of 348 herds were included in BVDV antibody testing, and 25.0% of tested herds were detected to be BVDV antibody positive. To recognise the BVDV-free status of the herd, the breeder should provide two consecutive tests with intervals of at least 6 months in all animals in the age from 7 to 13 months, with negative results for BVDV antibodies in ELISA. The BVDV-free status of the herd can be maintained by implementing preventive measures and can be renewed each year with one laboratory test in the age group of animals from 7 to 13 months for antibodies in ELISA. During the 7 years of the voluntary programme, 236 herds were included in the detection of BVDV in individual herds by real-time RT-PCR method and the elimination of positive animals from herds. In 71 (31.3%) herds, at least one BVDV-positive animal was detected, with the identification of a total of 267 persistently infected (PI) animals, representing an average of 2.9% of tested animals. The cost of testing for an average herd, recognised as BVDV-negative, and maintaining its BVDV-free status within the implemented voluntary programme, was €97.64/year, while for the average positive herd, the laboratory costs for elimination of BVDV were €189.59/year. Only limited progress towards eradication at the national level has been achieved in Slovenia since 2014.

Investigation of persistent infection of bovine viral diarrhea virus (BVDV) in Holstein dairy cows

The aim of this study was to investigate the persistent infection (PI) of bovine viral diarrhea virus (BVDV) along with its coexistence between BVDV antibody titer and BVD virus in blood of Holstein dairy cows. Only large commercial farms (each contained < 1000-3000 unvaccinated cows) were included. There were 11 dairy cattle herds. They included nearly 20,000 dairy cows. Totally, 140 cows, > 3 months to almost 10 years old, were randomly sampled. Indirect enzyme-linked immunosorbent assay (ELISA) and reverse transcription-polymerase chain reaction (RT-PCR) were used to detect BVDV antibody and virus, respectively. The percent positivity (PP) < 14 and ≥ 14 values are interpreted negative and positive, respectively. Simultaneously, whole blood samples pooled in groups of 10 animals were used for molecular detection of BVDV. The results revealed that 138 (98.56%) out of 140 cows were positive for BVDV antibody, while the BVDV antigen was detected only in 2 (1.42%) cows, which were negative for BVDV antibody and so were considered as persistent infection (PI) cows. They were also retested 3 weeks apart. Since the results showed the strong coexistence between seropositivity and BVD virus, in the infected dairy cattle herds, the combination of simple ELISA and pooled whole blood RT-PCR strategy could be an achievable approach to detect PI animals.

Comparison of Tests for Detection of Bovine Viral Diarrhea Virus in Diagnostic Samples

Currently, a variety of tests are used to detect bovine viral diarrhea virus (BVDV) in persistently infected (PI) cattle. These tests include immunohistochemical staining (IHC), antigen capture enzyme-linked immunosorbent assay (ACE), virus isolation (VI), and reverse transcription-polymerase chain reaction (RT-PCR). However, a lack of methods standardization could compromise the ability to consistently identify animals infected with BVDV. This study evaluated the diagnostic proficiency of current methods for detecting BVDV in infected cattle using intra- and interlaboratory comparisons. Samples were collected from 4 animals more than 7 months of age (2 BVDV negative animals, a PI animal, and a PI animal that previously lacked detectable virus in serum as determined by VI). Samples were submitted to 23 participating diagnostic laboratories using the respective laboratory's standard submission protocol. Samples collected for submission included: 1) serum for ACE, RT-PCR, and VI; 2) whole blood for RT-PCR and VI; and 3) skin biopsies for ACE and IHC. The ACE performed on skin provided the greatest consistency in detecting positive samples and a perfect level of agreement among laboratories. Reverse transcription-polymerase chain reaction and IHC performed well by correctly identifying ≤85% of samples positive for BVDV. Virus isolation performed on serum yielded the lowest consistency in detecting positive samples and the lowest level of agreement. The level of agreement between laboratories for detecting BVDV in persistently infected cattle ranged from perfect to less than expected by chance. The variation between laboratories suggests a need for training opportunities in standardized laboratory protocols and proficiency testing.

Diagnosis and Control of Viral Diseases of Reproductive Importance: Infectious Bovine Rhinotracheitis and Bovine Viral Diarrhea

Both bovine viral diarrhea virus and bovine herpesvirus 1 can have significant negative reproductive impacts on cattle health. Vaccination is the primary control method for the viral pathogens in US cattle herds. Polyvalent, modified-live vaccines are recommended to provide optimal protection against various viral field strains. Of particular importance to bovine viral diarrhea control is the limitation of contact of pregnant cattle with potential viral reservoirs during the critical first 125 days of gestation.

Use of Genomic Tools to Improve Cattle Health in the Context of Infectious Diseases

Although infectious diseases impose a heavy economic burden on the cattle industry, the etiology of many disorders that affect livestock is not fully elucidated, and effective countermeasures are often lacking. The main tools available until now have been vaccines, antibiotics and antiparasitic drugs. Although these have been very successful in some cases, the appearance of parasite and microbial resistance to these treatments is a cause of concern. Next-generation sequencing provides important opportunities to tackle problems associated with pathogenic illnesses. This review describes the rapid gains achieved to track disease progression, identify the pathogens involved, and map pathogen interactions with the host. Use of novel genomic tools subsequently aids in treatment development, as well as successful creation of breeding programs aimed toward less susceptible livestock. These may be important tools for mitigating the long term effects of combating infection and helping reduce the reliance on antibiotic treatment.

Bovine Viral Diarrhea Virus Infections

Bovine viral diarrhea virus (BVDV) continues to be of economic significance to the livestock industry in terms of acute disease and fetal loss. Many of the lesions relating to BVDV infection have been well described previously. The virus is perpetuated in herds through the presence of calves that are persistently infected. Relationships between various species and biotypes of BVDV and host defenses are increasingly understood. Understanding of the host defense mechanisms of innate immunity and adaptive immunity continues to improve, and the effects of the virus on these immune mechanisms are being used to explain how persistent infection develops. The noncytopathic biotype of BVDV plays the major role in its effects on the host defenses by inhibiting various aspects of the innate immune system and creation of immunotolerance in the fetus during early gestation. Recent advances have allowed for development of affordable test strategies to identify and remove persistently infected animals. With these improved tests and removal strategies, the livestock industry can begin more widespread effective control programs.

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.

Group testing in heterogeneous populations by using halving algorithms

Group (pooled) testing is often used to reduce the total number of tests that are needed to screen a large number of individuals for an infectious disease or some other binary characteristic. Traditionally, research in group testing has assumed that each individual is independent with the same risk of positivity. More recently, there has been a growing set of literature generalizing previous work in group testing to include heterogeneous populations so that each individual has a different risk of positivity. We investigate the effect of acknowledging population heterogeneity on a commonly used group testing procedure which is known as 'halving'. For this procedure, positive groups are successively split into two equal-sized halves until all groups test negatively or until individual testing occurs. We show that heterogeneity does not affect the mean number of tests when individuals are randomly assigned to subgroups. However, when individuals are assigned to subgroups on the basis of their risk probabilities, we show that our proposed procedures reduce the number of tests by taking advantage of the heterogeneity. This is illustrated by using chlamydia and gonorrhoea screening data from the state of Nebraska.

Prevalence study of Bovine viral diarrhea virus by evaluation of antigen capture ELISA and RT-PCR assay in Bovine, Ovine, Caprine, Buffalo and Camel aborted fetuses in Iran

Bovine viral diarrhea virus is a pestivirus in the family Flaviviridae that cause abortions and stillbirths in livestock and its traditional diagnosis is based on cell culture and virus neutralization test. In this study, for more sensitive, specific detection and determined the prevalence of virus in aborted Bovine, Ovine, Caprine, Buffalo and Camel fetuses the antigen capture ELISA and RT-PCR were recommended. From the total of 2173 aborted fetuses, 347 (15.96%) and 402 (18.49%) were positive for presence of Bovine viral diarrhea virus by antigen capture ELISA and RT-PCR respectively. Statistical analysis of data showed significant differences between ELISA and RT-PCR for detection of virus in aborted fetuses.

These results indicate a high presence of this pathogen in Iran and that RT- PCR is considerably faster and more accurate than ELISA for identification of Bovine viral diarrhea virus.

To our knowledge the Camels and Bovine are the most resistant and sensitive to Bovine viral diarrhea's abortions respectively and the prevalence of virus in Caprine is more than Ovine aborted fetuses. This study is the first prevalence report of Bovine viral diarrhea virus in aborted Bovine, Ovine, Caprine, Buffalo and Camel fetuses by evaluation of ELISA and RT-PCR in Iran.

Development of one-step SYBR Green real-time RT-PCR for quantifying bovine viral diarrhea virus type-1 and its comparison with conventional RT-PCR

Background

Bovine viral diarrhea virus (BVDV) is a worldwide pathogen in cattle and acts as a surrogate model for hepatitis C virus (HCV). One-step real-time fluorogenic quantitative reverse transcription polymerase chain reaction (RT-PCR) assay based on SYBR Green I dye has not been established for BVDV detection. This study aims to develop a quantitative one-step RT-PCR assay to detect BVDV type-1 in cell culture.

Results

One-step quantitative SYBR Green I RT-PCR was developed by amplifying cDNA template from viral RNA and using in vitro transcribed BVDV RNA to establish a standard curve. The assay had a detection limit as low as 100 copies/ml of BVDV RNA, a reaction efficiency of 103.2%, a correlation coefficient (R²) of 0.995, and a maximum intra-assay CV of 2.63%. It was 10-fold more sensitive than conventional RT-PCR and can quantitatively detect BVDV RNA levels from 10-fold serial dilutions of titrated viruses containing a titer from 10^-1 to 10^-5 TCID₅₀, without non-specific amplification. Melting curve analysis showed no primer-dimers and non-specific products.

Conclusions

The one-step SYBR Green I RT-PCR is specific, sensitive and reproducible for the quantification of BVDV in cell culture. This one-step SYBR Green I RT-PCR strategy may be further optimized as a reliable assay for diagnosing and monitoring BVDV infection in animals. It may also be applied to evaluate candidate agents against HCV using BVDV cell culture model.

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 realtime 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 ( R2 = 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.

Epidemiology and control of BVD in the U.S

The apparent prevalence of bovine viral diarrhea virus (BVDV) persistently infected cattle has been found to be low in U.S. dairies, beef herds and feedlots. Current management practices within U.S. cattle industries that impact the epidemiology of BVDV infections include purchasing untested cattle, lack of biosecurity procedures, large herd sizes, mixing cattle from multiple sources, high cattle densities in dairy and feedlot operations, synchronous breeding of beef herds, communal grazing and widespread vaccination. Evidence for BVDV infection has been found in farmed and free-ranging wildlife in North America; however the risk of BVDV transmission from wildlife to cattle is not known. The perception of a low prevalence of BVDV herd infections, the unrestricted sale of PI cattle, lack of economic data, intensive marketing of vaccines, reluctance to accept federal regulations, and a "gambler's" attitude among producers are impediments to implementation of a national systematic BVD control program. Since 2004, voluntary BVDV control programs have been organized in nine states reflecting the recognition of BVD as an important and preventable problem in the U.S.

Detection of Border Disease Virus in Fetuses, Stillbirths, and Newborn Lambs from Natural and Experimental Infections

The purpose of the present study was to evaluate the use of enzyme-linked immunosorbent assay (ELISA) antigen detection in blood or fetal fluids and reverse transcription polymerase chain reaction (RT-PCR) amplification in tissues for routine laboratory diagnosis of Border disease virus (BDV) infection. Samples from 67 fetuses, 6 stillbirths, and 11 lambs from 25 commercial flocks with suspicion of BDV abortion and 3 fetuses, 7 stillbirths, and 15 lambs obtained from an experimental infection with a local isolate (BDV genotype 4) were investigated. Presence of BDV was detected by RT-PCR in 7.9% of fetuses, 50% of stillbirths, and 50% of lambs from the commercial flocks analyzed, corresponding to 8 of the 25 farms (32%). A similar percentage of the lambs and stillbirths from the experimental infection were positive by RT-PCR of tissue samples (54.5%), and the highest positivity was detected in lymph node, thyroid gland, and kidney. The current study revealed that RT-PCR analysis of stillbirths and lambs with clinical symptoms is more suitable than the analysis of fetuses to confirm the presence of BDV in a flock. Pestiviral antigen was detected by antigen ELISA in a high proportion of fetuses (24/58) and stillbirths (3/4) from commercial flocks, but in lambs, the presence of colostral antibodies masked the detection of the antigen by ELISA. Nevertheless, in lambs from the experimental infection that were not fed colostrum, antigen ELISA was less efficient than RT-PCR in detecting viral presence in stillbirths and lambs. Antigen ELISA is therefore recommended for fetuses with advanced autolysis that can adversely affect RNA integrity.

Serological Evaluation of Precolostral Serum Samples to Detect Bovine Viral Diarrhea Virus Infections in Large Commercial Dairy Herds

The authors propose that screening newborn calves for Bovine viral diarrhea virus (BVDV) antibody prior to colostrum feeding is a useful strategy to detect herds with endemic BVDV infection. In the current study, precolostral serum samples of newborn calves in 2 Minnesota and 2 California dairy farms were examined. Precolostral BVDV antibodies were detected by serum neutralization and enzyme-linked immunosorbent assay in 7.4% (33/446) and 6.2% (32/515) of newborn calves in the California and Minnesota herds, respectively. The serum samples were also tested by reverse transcription polymerase chain reaction (RT-PCR), and BVDV was detected in 1.6% (7/446) and 3.5% (18/515) of newborn calves in the California and Minnesota herds, respectively. The primary advantages of precolostral testing are that calves congenitally infected with BVDV and seropositive at birth represent a larger percentage of calves born than BVDV-viremic calves and that fewer animals would need to be tested with an antibody test than a RT-PCR or antigen detection test to detect endemic BVDV infections at the herd level. Testing for BVDV antibody in calves prior to colostrum feeding detects fetal infections in both late-gestating cows and nonlactating heifers. Precolostral serum antibody detection is not confounded by vaccination and may be a more sensitive screening method than bulk milk RT-PCR and nonvaccinated sentinel calf strategies in large dairy herds.

A survey of bovine viral diarrhea virus testing in diagnostic laboratories in the United States from 2004 to 2005

Bovine viral diarrhea virus (BVDV) has a great economic impact on the United States cattle industry. The Academy of Veterinary Consultants, the American Association of Bovine Practitioners, and the National Cattlemen's Beef Association have called for the goal of BVDV control and eventual eradication in the U.S.A. One of the key factors in such efforts will be the detection of BVDV infections, particularly targeting persistently infected animals. To assess current BVDV detection methods in the U.S.A., 26 veterinary diagnostic laboratories in 23 states were surveyed. Survey questions related to the types of tests currently offered, the number of tests performed, the reasons for test requests, the type of samples used, whether sample pooling was performed, and whether follow-up testing or information regarding bovine viral diarrhea (BVD) management was provided after positive tests. There was no clear consensus on an individual BVDV testing method, the pooling of samples or the retesting of positive animals. Ear-notch antigen capture enzyme-linked immunosorbent assay (ACE) was the test most frequently performed based on the absolute number of tests. However, when the data were adjusted to reflect individual laboratory choices, the number of ACE and immunohistochemistry tests performed on ear notches was nearly equal. Only 55% of diagnostic laboratories provided BVD management information to producers or veterinarians who submitted positive samples. There was no significant difference in the number of positive tests in laboratories that received the majority of their samples for screening purposes versus laboratories that received the majority of their samples because BVDV was suspected based on clinical signs in a herd.

Sensitivity of Polymerase Chain Reaction for Detection of Bovine Viral Diarrhea Virus in Pooled Serum Samples and Use of Pooled Polymerase Chain Reaction to Determine Prevalence of Bovine Viral Diarrhea Virus in Auction Market Cattle

Two reverse transcription-nested polymerase chain reaction tests, 1 quantitative (qRT-nPCR) and 1 standard (RT-nPCR), were evaluated to assess sensitivity for detection of bovine viral diarrhea virus (BVDV) of a single positive serum sample in a pool of 30. The RT-nPCR and qRT-nPCR each detected 95 of 100 known positives. The RT-nPCR was used to estimate the prevalence of BVDV in adult beef cows. Serum samples were obtained from the US Department of Agriculture brucellosis testing laboratories in 3 Midwestern states. Samples originated from auction markets and private treaty sales throughout the 3 states. A total of 2,990 serum samples were collected and randomly pooled into 100 pools for testing. Two of the 100 pools of field samples were positive, and each positive pool had a single positive individual sample upon confirmation. The estimate of BVDV prevalence in adult cows in this study was 0.07%. This study estimates the diagnostic sensitivity of RT-nPCR for BVDV and confirms that it is a useful diagnostic tool for pools of 30 serum samples and that prevalence of BVDV in adult cattle from auction markets is low.

Infectious causes of bovine abortion during mid- to late-gestation

The accurate and prompt diagnosis of infectious abortions in a herd requires cooperation between the herd veterinarian and a veterinary diagnostic laboratory; working together, with good communication and appropriate sampling and testing, the chances of obtaining an etiologic diagnosis are improved. Abortion diagnosis is a challenge as a cause is usually identified in less than half of submitted fetuses. The majority of diagnosed abortions are attributed to infections by a moderate number of bacterial, viral, fungal and protozoal agents. The pathology and other findings used in the laboratory diagnosis of the major infectious agents causing bovine abortion in mid- to late-gestation will be discussed.

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

OBJECTIVE

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).

DESIGN

Cross-sectional study.

SAMPLE POPULATION

174 pooled supernatant samples representing 12,528 animals between 1 and 12 months old.

PROCEDURES

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

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.

CONCLUSIONS AND CLINICAL RELEVANCE

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%).