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

The Epidemiology and Control of Bovine Viral Diarrhoea Virus in Tropical Indonesian Cattle

This review aims to update the knowledge of the epidemiology of Bovine viral diarrhoea virus (BVDV) in Indonesia and Southeast Asia and provide a perspective on the control options for BVDV in the Indonesian cattle population in the future. Studies on BVDV in Indonesia, since its first report in that country, and the updated beef and dairy cattle industries are reviewed. In ten of 34 provinces, BVDV is endemic. The subgenotypes of BVDV-1a and BVDV-1c are predominant in Indonesian cattle. However, BVDV is currently not a priority disease to control in Indonesia. Cattle imports from Australia appear to be potentially the most significant source of transmission of BVDV into native cattle, but the control of BVDV conducted in the local quarantine facilities is currently not achieving the aim of controlling BVDV; thus, complementary measures are needed. With the small-scale nature of the vast majority of cattle breeding in the country, the control of BVDV in provinces in which cattle breeding is economically essential may need to be organised by regional and provincial governments. Gaps in our knowledge of BVDV are identified in this review, and strategies for the control of BVDV in Indonesia are discussed.

Temporal trends in bulk tank milk antibody ELISA and PCR test results for bovine viral diarrhoea in New Zealand pastoral dairy herds

Aims: To describe temporal trends in bulk milk antibody ELISA and PCR testing for bovine viral diarrhoea (BVD) in New Zealand pastoral dairy herds and to assess the use of historical accession data to predict herd-level BVD incursions. Methods: Data on all diagnostic testing of bulk milk for BVD performed by the Livestock Improvement Corporation (Hamilton, NZ) over eight lactation seasons from 1 June 2010 to 31 May 2018 were analysed. This included anonymised herd identification, geographic location, herd size, sample collection date, sample to positive (S/P) ratio for antibody ELISA results, and cycle threshold values for PCR detecting viral RNA. Multivariable logistic regression was used to explore the relationship between historical accession data and the risk of herds having at least one positive bulk milk PCR test result in the 2017 season. Results: There were 156,034 bulk milk BVD diagnostic testing accessions for 10,495 uniquely identified dairy herds over the 8-season period. The prevalence of tested herds with at least one positive bulk milk PCR test result decreased from 14.6% (407/2,786) in the 2010 season to 5.6% (355/6,309) in the 2017 season with similarly marked declines in S/P ratios. In the 2017 season, 2,961/6,309 (46.9%) herds had S/P ratios greater than the 0.75 cut-off value indicating recent or active BVD virus transmission within the herd while 1,422/6,309 (22.5%) herds were classified as having negative or low S/P ratios. Herds that cleared BVD from the milking herd experienced a mean decline in S/P ratio of 0.11 units per year (min 0.05; max 0.18). In the multivariable analysis, the overall incidence risk of herds experiencing a BVD incursion in the 2017 season was 3.8% (146/3,848) and there were three significant predictors in the final model: herd size, PCR status in the 2014 season, and change in S/P ratio between the 2014 and 2015 seasons. The area under the receiver operating curve for the final model was 0.695 indicating poor discrimination. Conclusions and clinical relevance: The prevalence of dairy herds in New Zealand with positive bulk milk PCR test results and high S/P ratios has decreased over time, suggesting fewer herds are actively infected with BVD and that herd immunity may also be declining. Although monitoring trends in bulk milk test results provides useful information on changes in individual herd status, it is difficult to accurately predict when new incursions will occur and farmers should continue to maintain good biosecurity.

Assessing the use of diagnostic laboratory accession data to support national bovine viral diarrhoea control in New Zealand

Aims: To assess the suitability of using existing national diagnostic laboratory testing data to support national bovine viral diarrhoea (BVD) research, surveillance, and control in New Zealand. Methods: Data on laboratory accessions for BVD diagnostic testing in New Zealand from 1 January 2015 to 31 December 2017 were provided by four commercial veterinary diagnostic companies. The data were integrated into a single dataset containing the unique accession number, sample submission date, farm location (territorial authority level), test type (bulk milk antibody-ELISA, bulk milk PCR, serum antibody-ELISA, blood/serum/tissue antigen-ELISA, or blood/serum/tissue PCR), and test results. Estimates for the number of registered cattle farms in each territorial authority were generated from the National Animal Identification and Tracing database. Results were summarised for July 2015 to June 2016 and July 2016 to June 2017. Results: There was a total of 59,007 unique BVD diagnostic test accessions including 39,920 (67.6%) for bulk milk antibody-ELISA, 27,832 (47.2%) for bulk milk PCR, 3,229 (5.5%) for serum antibody-ELISA, 9,132 (15.5%) for blood/serum/tissue antigen-ELISA, and 7,122 (12.1%) for blood/serum/tissue PCR. Of the 17,946 accessions for blood/serum/tissue samples, 4,316 (24.0%) were missing the herd production type and 6,678 (37.2%) were missing the animals age. Approximately 7,000/10,958 (65%) dairy herds and 1,600/43,611 (4%) beef herds were conducting annual BVD screening tests. In 2016/2017, the prevalence of accessions with ≥1 BVD-positive result was 40.6% for bulk milk antibody, 6.4% for bulk milk PCR, 45.6% for serum antibody, and 9.8% for blood/serum/tissue antigen-ELISA or PCR tests. There was substantial regional variation in both the percentage of herds testing for BVD and the prevalence of positive accessions. Following pooled serum antibody-ELISA, only 175/604 (29.0%) beef herds and 177/566 (31.3%) dairy herds had recorded follow-up testing. Conclusions and Clinical Relevance: Laboratory diagnostic accession data has the potential to provide valuable insights about BVD epidemiology in New Zealand, but there are significant limitations in the data collected and discrepancies in the different systems that each laboratory uses to measure, interpret, and record diagnostic data. There is a strong need to develop a more consistent national system for recording and sharing BVD test results to support BVD management at farm and industry levels. Abbreviations: BVD: Bovine viral diarrhoea; Ct: Cycle threshold; NAIT: National Animal Identification and Tracing; NZVP: New Zealand Veterinary Pathology; PI: Persistently infected; S/P: Sample to positive control.

Global knowledge gaps in the prevention and control of bovine viral diarrhoea (BVD) virus

The significant economic impacts of bovine viral diarrhoea (BVD) virus have prompted many countries worldwide to embark on regional or national BVD eradication programmes. Unlike other infectious diseases, BVD control is highly feasible in cattle production systems because the pathogenesis is well understood and there are effective tools to break the disease transmission cycle at the farm and industry levels. Coordinated control approaches typically involve directly testing populations for virus or serological screening of cattle herds to identify those with recent exposure to BVD, testing individual animals within affected herds to identify and eliminate persistently infected (PI) cattle, and implementing biosecurity measures such as double-fencing shared farm boundaries, vaccinating susceptible breeding cattle, improving visitor and equipment hygiene practices, and maintaining closed herds to prevent further disease transmission. As highlighted by the recent DISCONTOOLS review conducted by a panel of internationally recognized experts, knowledge gaps in the control measures are primarily centred around the practical application of existing tools rather than the need for creation of new tools. Further research is required to: (a) determine the most cost effective and socially acceptable means of applying BVD control measures in different cattle production systems; (b) identify the most effective ways to build widespread support for implementing BVD control measures from the bottom-up through farmer engagement and from the top-down through national policy; and (c) to develop strategies to prevent the reintroduction of BVD into disease-free regions by managing the risks associated with the movements of animals, personnel and equipment. Stronger collaboration between epidemiologists, economists and social scientists will be essential for progressing efforts to eradicate BVD from more countries worldwide.

Serosurvey for Infectious Agents Associated with Subfertility and Abortion in Dairy Cattle in Trinidad and Tobago, West Indies

Despite frequent reports of subfertility and abortion in dairy cattle in Trinidad and Tobago (T&T), little is known about the potential infectious and non-infectious causes. This study set out to investigate possible infectious causes of reproductive problems by measuring the seroprevalence of four of the most significant reproductive pathogens in dairy cattle worldwide: Brucella abortus (B. abortus); Neospora caninum (N. caninum), Bovine Viral Diarrhoea virus (BVDV), and Infectious Bovine Rhinotracheitis virus (IBRV). These four reproductive pathogens have been suspected to be present in dairy cattle in T&T for some time but, previously, studies have not been carried out to confirm their presence. Bulk milk samples were collected from 92 dairy farms across Trinidad, representing a total of 1177 dairy cattle. Four dairy farms were selected for individual milk sampling to assess in-farm seroprevalence levels. Milk samples were tested for antibodies to the four pathogens by commercial ELISA kits. The overall farm seroprevalence was 62% for N. caninium and 23% for IBRV, and no antibodies were detected in any of the bulk milk samples for B. abortus or BVDV. Mixed infections for IBRV and N. caninum were common. Seroprevalence levels were between 8% and 65% for N. caninum and between 3% and 53% IBRV on the four individual farms. These results reveal the presence of IBRV and N. caninum for the first time on the island of Trinidad and importantly reveal no evidence for the circulation of BVDV or B. abortus in dairy cattle in Trinidad.

Molecular detection and characterization of transient bovine viral diarrhea virus (BVDV) infections in cattle commingled with ten BVDV persistently infected cattle

Fifty-three cattle of unknown serologic status that were not persistently infected (PI) with bovine viral diarrhea virus (BVDV) were commingled with 10 cattle that were PI with different strains of BVDV, and were monitored for an extended commingle period using a reverse-transcription real-time PCR (RT-rtPCR) BVDV assay on various sample types. Transient infections with BVDV were also assessed by virus isolation, virus neutralization (VN) assays, and direct buffy coat 5'-UTR sequencing. Infections were demonstrated in all cattle by RT-rtPCR; however, the detection rate was dependent on the type of sample. Buffy coat samples demonstrated a significantly greater number of positive results ( p ≤ 0.05) than either serum or nasal swab samples. Presence of elevated BVDV VN titers at the onset inversely correlated with the number of test days positive that an individual would be identified by RT-rtPCR from buffy coat samples, and directly correlated with the average Ct values accumulated over all RT-rtPCR test days from buffy coat samples. Both single and mixed genotype/subgenotype/strain infections were detected in individual cattle by direct sample 5'-UTR sequencing. A BVDV-2a strain from a PI animal was found to be the predominant strain infecting 64% of all non-PI cattle; BVDV-1b strains originating from 3 PI cattle were never detected in non-PI cattle. Although direct sample 5'-UTR sequencing was capable of demonstrating mixed BVDV infections, identifying all strains suspected was not always efficient or possible.

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.

Bovine viral diarrhea virus type 2 in vivo infection modulates TLR4 responsiveness in differentiated myeloid cells which is associated with decreased MyD88 expression

Symptoms of bovine viral diarrhea virus (BVDV) infection range from subclinical to severe, depending on strain virulence. Several in vitro studies showed BVDV infection impaired leukocyte function. Fewer studies have examined the effects of in vivo BVDV infection on monocyte/macrophage function, especially with strains of differing virulence. We characterized cytokine production by bovine myeloid cells isolated early or late in high (HV) or low virulence (LV) BVDV2 infection. Given BVDV infection may enhance susceptibility to secondary bacterial infection, LPS responses were examined as well. Monocytes from HV and LV infected calves produced higher levels of cytokines compared to cells from controls. In contrast, monocyte-derived macrophage cytokine levels were generally reduced. Modulated cytokine expression in HV BVDV2 macrophages was associated with decreased MyD88 expression, likely due to its interaction with viral NS5A. These data and those of others, suggest that certain Flaviviridae may have evolved strategies for subverting receptor signaling pathways involving MyD88.

Prevalence and spatial distribution of antibodies to bovine viral diarrhea virus and Coxiella burnetii in white-tailed deer (Odocoileus virginianus) in New York and Pennsylvania

Significant pathogens of domestic livestock and public-health related pathogens, such as bovine viral diarrhea virus (BVDV) and Coxiella burnetii, are commonly diagnosed in some wildlife species. BVDV is an economically important pathogen of domestic bovids and Coxiella burnetii is a highly infectious zoonotic bacterium. As a result of recent shifting patterns of disease, it is critical that baseline information regarding the status of both significant pathogens of domestic livestock and public-health related pathogens are established for commonly encountered wildlife such as white-tailed deer (Odocoileus virginianus). White-tailed deer are susceptible to both BVDV and C. burnetii infection, and the purpose of this study was to investigate for the presence of antibodies to these two pathogens in New York and Pennsylvania white-tailed deer. Exposure to BVDV and C. burnetii was determined using sera collected from 333 (219 males and 114 females) wild white-tailed deer in New York and 291 (130 males and 161 females) wild white-tailed deer from Pennsylvania. Samples were collected from hunter-harvested deer in central New York State in 2009 and live-captured deer in Pennsylvania in 2010. Sera were screened for anti-BVDV antibodies via a commercial blocking BVDV enzyme-linked immunosorbent assay. Coxiella burnetii phase II whole-cell antigen-coated slides were used to screen sera via an indirect microimmunofluorescence assay. Antibody prevalence was compared by sex class and location of collection. Deer in New York had higher antibody prevalence to BVDV (6.01%) than did deer in Pennsylvania (0.34%). Conversely, C. burnetii phase II antibodies were more common in Pennsylvania (20.96%) than in New York (14.41%). No statistically significant difference between locations was observed in either BVDV or C. burnetii antibody prevalence when data were analyzed by sex-class. Overall, C. burnetii seroprevalence was not significantly higher in Pennsylvania than in New York.

Development of a novel diagnostic test for detection of bovine viral diarrhea persistently infected animals using hair

The purpose of this study was to determine whether manually plucked hairs might serve as an alternative sample for a quantitative real time polymerase chain reaction (qRT-PCR) testing. Twenty three, 1~3 week old, non-bovine viral diarrhea virus (BVDV) vaccinated calves, found to be positive for BVDV by immunohistochemical staining, were selected and hairs were manually plucked from the ear. qRT-PCR was performed on samples consisting of more than 30 hairs (30~100) and whole blood. All 23 animals were positive for the virus by qRT-PCR performed on the whole blood and when samples of more than 30 hairs were assayed. Additionally, qRT-PCR was performed on groups of 10 and 20 hairs harvested from 7 out of 23 immunohistochemical staining-positive calves. When groups of 20 and 10 hairs were tested, 6 and 4 animals, respectively, were positive for the virus.

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.

Spatial modelling of the between-herd infection dynamics of bovine virus diarrhoea virus (BVDV) in dairy herds in Denmark

According to the current literature BVDV-infected neighbours probably impose a high risk of infection of susceptible cattle herds. In the present study, the objective was to evaluate the risk of a dairy herd changing infection status (from not having persistently infected (PI) animals to having PI-animals) in relation to location and infection status of neighbouring cattle herds in Denmark. In total, 7921 dairy herds were included in the analysis of spatial and non-spatial risk factors. The spatial risk factors were derived based on the cattle herds in the neighbourhood (N=36,639 cattle herds). The neighbourhood was defined as the first order neighbouring cattle herds using a Delauney triangularization. In total, 13.3% of the dairy herds changed herd status to PI-herds during the study period that lasted from January 1, 1995, to June 30, 1996. The risk of becoming a PI-herd was negatively associated with the mean distance to the neighbouring herds (OR=0.7 for an increase of 1 km). Presence of PI-herds in the neighbourhood increased the risk of becoming a PI-herd (OR=1.37, 1.40, 1.70 for 1, 2, ≥3 PI-herds in the neighbourhood). Increasing herd size increased the risk of becoming a PI-herd (OR=3.9 for an increase of 10 cows). Regional differences were seen.

The first report on the prevalence of pestivirus infection in camels in Sudan

The role of pestivirus particularly bovine viral diarrhea virus (BVDV) in causing respiratory infections in camels was studied in four different localities in Sudan. The evaluation was carried out using ELISA, and positive specimens were further tested using direct fluorescent antibody technique (FAT) and reverse transcriptase polymerase chain reaction (RT-PCR) for confirmation. The overall detected seroprevalence of BVD in camel sera was 84.6% with the highest prevalence in Western Sudan (92.5%) and with most of positives showing 2+ and 3+ titer. Out of 186 lung specimens examined for BVDV antigen, 13 were found positive (7%) with the highest prevalence in Central Sudan. All ELISA-positive specimens were positive using FAT and RT-PCR. To our knowledge, this is the first report for the detection of BVDV antigen and antibodies in camels in Sudan.

Prevalence and Characterization of Bovine Viral Diarrhea Virus in the White-Tailed Deer Population in Indiana

Bovine viral diarrhea (BVD) is one of the economically important diseases of cattle. For many years, different types of vaccines have been commercially available, yet this disease is hard to control in high-density population areas. Detection and isolation of bovine viral diarrhea virus (BVDV) from any potential reservoir is vital, especially when considering virus eradication from a herd or locale. One potential source is wild ruminants. Ear notches and lymph nodes were collected from the wild population of white-tailed deer (Odocoileus virginianus) during deer hunting season in Indiana and tested for BVDV with a commercial BVD antigen capture enzyme-linked immunosorbent assay. Two samples out of 745 collected samples were positive, and subsequently cp and ncp BVDV was isolated from 1 ear notch and 1 lymph node. These isolates were genotyped as type 1a and 1b based on sequence analysis of the 5′ untranslated region (UTR). The results of the present study indicate that the prevalence of BVDV in the white-tailed deer population of Indiana is about 0.3%. Wild ruminants infected with BVDV should be taken into consideration during an eradication program of BVDV from the livestock population.