ORCID Profile
0000-0003-4473-9213
Current Organisation
University of Adelaide
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Publisher: Elsevier BV
Date: 09-2016
Publisher: SAGE Publications
Date: 26-03-2016
Abstract: Antigen enzyme-linked immunosorbent assay (ELISA) is used for the detection of Bovine viral diarrhea virus persistently infected (BVDV PI) cattle however, colostrum-derived antibodies may interfere with antigen detection in serum from young PI calves. Our study aimed to assess serum pretreatment methods for reducing such interference. Dilution of PI serum with serum containing specific antibody showed that antibody levels equivalent to those observed in colostrum-fed calves were able to eliminate all antigen signals in a serum s le. Serum was treated with ethylenediamine tetra-acetic acid at pH 4.5, 5.5, 6.5, and 7.5, then boiled, centrifuged, and the supernatant-recovered. BVDV antibody was undetectable by ELISA in supernatants from treated s les, and the antigen ELISA signal was improved. Maximum antigen signal recovery of % was achieved at pH 5 ± 0.5. When this optimal treatment method was applied to field s les from 3 PI calves (which were negative in the antigen-capture ELISA without treatment), the antigen signal improved and gave a positive result in each case. Pretreatment may provide an improvement in the detection of young PI calves.
Publisher: Elsevier BV
Date: 02-2014
DOI: 10.1016/J.TVJL.2013.07.024
Abstract: Bovine viral diarrhoea virus (BVDV) is the most prevalent infectious disease of cattle. It causes financial losses from a variety of clinical manifestations and is the subject of a number of mitigation and eradication schemes around the world. The pathogenesis of BVDV infection is complex, with infection pre- and post-gestation leading to different outcomes. Infection of the dam during gestation results in fetal infection, which may lead to embryonic death, teratogenic effects or the birth of persistently infected (PI) calves. PI animals shed BVDV in their excretions and secretions throughout life and are the primary route of transmission of the virus. These animals can usually be readily detected by virus or viral antigen detection assays (RT-PCR, ELISA), except in the immediate post-natal period where colostral antibodies may mask virus presence. PI calves in utero (the 'Trojan cow' scenario) currently defy detection with available diagnostic tests, although dams carrying PI calves have been shown to have higher antibody levels than seropositive cows carrying non-PI calves. Acute infection with BVDV results in transient viraemia prior to seroconversion and can lead to reproductive dysfunction and immunosuppression leading to an increased incidence of secondary disease. Antibody assays readily detect virus exposure at the in idual level and can also be used in pooled s les (serum and milk) to determine herd exposure or immunity. Diagnostic tests can be used to diagnose clinical cases, establish disease prevalence in groups and detect apparently normal but persistently infected animals. This review outlines the pathogenesis and pathology of BVD viral infection and uses this knowledge to select the best diagnostic tests for clinical diagnosis, monitoring, control and eradication efforts. Test methods, types of s les and problems areas of BVDV diagnosis are discussed.
Publisher: SAGE Publications
Date: 08-02-2017
Abstract: Effective control and the eventual eradication of Bovine viral diarrhea virus (BVDV) from cattle populations depend on the accurate identification of infected animals. Although typically a disease agent of cattle, BVDV is known to infect a wide variety of nonbovine species, including sheep. However, validation of serologic tests in these nonbovine species, particularly sheep, is lacking. We analyzed 99 sheep sera (57 s les from Pestivirus-naive sheep, and 42 s les from BVDV-inoculated sheep) in order to investigate 3 serologic tests: the agarose gel immunodiffusion (AGID) and 2 commercial enzyme-linked immunosorbent assays (ELISAs) for detection of BVDV antibodies. At the manufacturer’s cutoff thresholds, the AGID performed with 95.2% diagnostic sensitivity ELISA-A performed with sensitivity of 90.5% and ELISA-B with 69.1%. All 3 tests performed with 100% diagnostic specificity. Two-graph receiver operating characteristic analysis showed that performance characteristics were optimized, such that both diagnostic sensitivity and diagnostic specificity were % for both ELISAs, if the thresholds were altered to 34.9% inhibition for ELISA-A and 63.5 signal-to-noise ratio for ELISA-B.
Publisher: Wiley
Date: 10-08-2020
DOI: 10.1111/AVJ.13004
Publisher: Wiley
Date: 17-06-2014
DOI: 10.1111/AVJ.12208
Abstract: Acute infection with bovine viral diarrhoea virus (BVDV) usually causes only mild clinical disease in cattle, but infection of animals of breeding age can result in immune suppression (resulting in an increased incidence and severity of secondary disease) and decreased reproductive performance. If infection occurs during pregnancy, the virus may cross the placenta and either cause abortion, establish immunotolerance and persistent infection (PI) in the fetus or cause congenital deformities. These outcomes depend on the stage of pregnancy at the time of infection. BVDV is recognised as a disease of significant financial impact in a number of countries. As a result, national and regional BVDV control programs are now in place in several regions around the world. In Europe, these programs largely rely on the identification and removal of the PI animals, whereas vaccination has tended to be the chosen method of control in the United States. BVDV is endemic in Australian cattle populations, with more than 80% of herds surveyed showing some level of exposure to the pathogen. The cost to the national industry is estimated to be AUD57.9 million annually. This review identifies and discusses the challenges to BVDV control in Australia, including farmer attitudes, herd size, sheep as a potential reservoir host and diagnostic capabilities. We conclude that systematic BVDV control in Australia is, or soon will be, an option however, detailed cost-benefit analyses will need to be undertaken.
Publisher: Elsevier BV
Date: 05-2012
DOI: 10.1016/J.VETPAR.2011.11.032
Abstract: A serological survey for Neospora caninum and Besnoitia besnoiti was carried out in beef and dairy cattle in South Australia. Serum s les of dairy cattle (n=133) from 9 properties and tank milk s les from a further 122 dairy herds were tested. An additional 810 sera from beef cattle from 51 properties were also tested. Testing at the in idual animal level by IDEXX NEOSPORA X2 Ab test ELISA revealed a low prevalence of N. caninum antibodies of only 2.7% (95% CI 1.6-3.7%) sera positive, as did the milk testing that showed 2.5% (95% CI 1.4-3.6%) of tank milks being positive. At the herd level, 29.4% (95% CI 16.9-41.9%) of beef, and 44.4% (95% CI 12.0-76.9%) of dairy cattle herds showed serum antibodies. The highest within-herd prevalence in beef was 20% and 25%in dairy, which explains the low herd prevalence in dairy detected by bulk milk testing. Testing for B. besnoiti antibodies by PrioCHECK(®) Besnoitia Ab 2.0 ELISA initially identified 18.4% (95% CI: 15.8-21.0%) of 869 in idual cattle sera as positive by ELISA at the manufacturer's suggested cut-off threshold (15 PP). Additional tests by immunoblot and IFAT, however, could not confirm any of the ELISA results. The use of a higher (40 PP) threshold in the ELISA is suggested to improve specificity. There is thus no evidence of B. besnoiti infection in South Australian cattle.
Publisher: Wiley
Date: 05-2015
DOI: 10.1111/AVJ.12316
Abstract: We aimed to establish the attitudes of South Australian cattle farmers towards endemic animal disease prevention and control, with a particular focus on the awareness of and attitudes towards bovine viral diarrhoea (BVD). This cross-sectional postal survey involved mailing a questionnaire to all South Australian cattle owners with 35 or more head of cattle. Worms and lice were the most common animal disease concerns. Less than half of responding farmers were adequately vaccinating their herds against clostridial diseases, but 53.0% stated that they utilised quarantine procedures. Less than 20% of respondents had actively taken part in BVD educational opportunities, or had vaccinated or tested their herd for BVD less than 20% of respondents were actively involved in any systematic control of Johne's disease. Overall, farmers' actual knowledge of BVD was lower than their perceived understanding, although their interest in BVD and its control was high. Disease prevention measures such as vaccination, quarantine and participation in systematic control schemes were used by a minority of respondents. The results suggest that respondents acknowledge BVD as an important and relevant disease, despite many believing it was not a problem in their herd. Interest in BVD appears to be high and it is likely that an education program would be well received.
Publisher: SAGE Publications
Date: 12-03-2014
Abstract: Testing for specific antibodies against Bovine viral diarrhea virus (BVDV) in pooled serum may present an opportunity to decrease the cost of screening for herds of high seroprevalence and increased likelihood of active infection. Experimental serum pools ( n = 280) were created by combining equal aliquots of serum from between 5 and 25 in iduals. A further 188 serum pools were generated from field serum s les. All pools and in idual sera were tested for BVDV-specific antibodies by enzyme-linked immunosorbent assay (ELISA), according to manufacturer’s instructions. Pools returned repeatable results, with coefficients of variation generally below 10%. The presence of serum from a persistently infected (PI) in idual in the pool had no significant effect on the ELISA s le-to-positive (S/P) ratio. The results revealed that a single strong antibody-positive in idual could maintain a positive result (at the manufacturer’s threshold) in pools of up to 128, while even a single weak-positive animal would generate a positive result in pools of up to 8. The S/P ratio of the pool was positively related to the within-pool prevalence of antibody-positive in iduals. However, as the strength of the in idual positive animals contributing to the pool had a large effect on the pool S/P ratio, the S/P ratio could not be used to accurately predict the within-pool prevalence of field serum pools. An alternative method of S/P ratio interpretation was pursued, and a two-graph receiver operating characteristic analysis allowed segregation of pools into low, medium, and high risk with good results when applied to field serum pools.
Publisher: Wiley
Date: 26-07-2018
DOI: 10.1111/AVJ.12709
Abstract: Bovine viral diarrhoea virus (BVDV) and border disease virus (BDV) are of the genus Pestivirus. They are known to cause significant reproductive and production losses, with BVDV acknowledged as a major source of economic loss to the Australian cattle industry. Very little is currently known about the prevalence and effect of pestiviruses in the Australian sheep industry. The present study aimed to examine the seroprevalence and effect of both BVDV and BDV in South Australian sheep flocks. In total, 875 breeding ewes on 29 properties were serologically tested by ELISA, AGID and VNT assays for the presence of Pestivirus-specific antibodies. Three (0.34%) in idual animals returned serological results suggestive of previous BDV infection. All three positive animals were collected from one property, giving a property level seroprevalence of 3.45% and a within-flock seroprevalence of 10%. The results suggested that BDV infection is present, albeit at a very low incidence, in the South Australian sheep flock and BVDV infection appears to be absent. Consequently, pestiviruses are unlikely to impair production in South Australian sheep populations.
Publisher: Wiley
Date: 26-06-2014
DOI: 10.1111/AVJ.12188
Abstract: The aims of this study were to evaluate a commercially available ELISA for the detection of bovine viral diarrhoea virus (BVDV)-specific antibodies in in idual milk compared with in idual serum s les, and in bulk milk s les compared with within-herd antibody prevalence and bulk milk quantitative reverse transcription polymerase chain reaction (qRT-PCR) results. Paired in idual serum and in idual milk s les were collected from 125 lactating cows and tested by ELISA 96 bulk milk s les were also tested. Within-herd antibody prevalence was calculated based on milk ELISA results for 25 in idual cows in each herd. Additionally, 167 bulk milk s les were tested for BVDV-specific antibodies by ELISA and for the presence of BVDV by qRT-PCR to establish the correlation between antibody result and virus presence. Good agreement was observed between in idual milk and serum results (Kappa = 0.865). The ELISA was observed to detect BVDV-specific antibodies in in idual milk s les with a relative sensitivity of 96.6% and specificity of 89.2%. The bulk milk s les revealed a strong (r(2) = 0.95) relationship between the ELISA result and the within-herd antibody prevalence. The proportion of herds that tested positive by bulk milk qRT-PCR increased as the bulk milk antibody S/P ratio increased. Commercially available ELISA testing of in idual and bulk milk s les is an appropriate alternative to serum testing with good test performance in these s les. Determining a threshold for the detection of herds containing active BVD infection by testing bulk milk is a novel use for an antibody ELISA kit and provides more practical, relevant test results.
Publisher: Wiley
Date: 30-10-2013
DOI: 10.1111/J.1751-0813.2012.01010.X
Abstract: To compare the performance of an enzyme-linked immunosorbent assay (ELISA) for the detection of antibodies specific to bovine viral diarrhoea virus (BVDV) with a virus neutralisation test (VNT) and agarose gel immunodiffusion (AGID) test. A total of 125 cattle serum s les were tested by a commercially available ELISA for antibodies specific to BVDV and by a VNT as the reference standard. A comparison between AGID and ELISA for detection of BVDV antibodies was also carried out, using 1182 serum s les from unvaccinated South Australian cattle. Two-graph receiver operating characteristics (TG-ROC) analysis was used to confirm that the manufacturer's recommended cut-off value for the ELISA was appropriate. Two-by-two tables were constructed to analyse the concordance of serological results among the three assays. McNemar tests were used to assess the agreement among serological tests. Using the manufacturer's cut-off threshold, supported by TG-ROC analysis, the ELISA's sensitivity and specificity were calculated to be 96.7% and 97.1%, respectively, compared with the VNT. Compared with AGID, ELISA with specific BVDV antibodies may be more sensitive and detect 5.8% more s les than AGID. McNemar test also showed a significant difference (P < 0.001) between AGID and ELISA.
Publisher: SAGE Publications
Date: 16-09-2014
Abstract: The diagnosis of neonatal and young calves persistently infected (PI) with Bovine viral diarrhea virus (BVDV) by antigen-capture enzyme-linked immunosorbent assay (ACE) may be complicated by interference from colostrum-derived specific antibodies. Ten calves, with 3 calves identified as PI and 7 as non-PI were used in the current study. All non-PI calves were shown to be seropositive for BVDV-specific antibodies by antibody enzyme-linked immunosorbent assay (Ab-ELISA) on serum. Serum s les, ear notch s les, and nasal and saliva swabs were collected from each calf from birth until 12 weeks of age and tested by ELISA for BVDV-specific antigen and antibodies. Following colostrum ingestion, Ab-ELISA s le-to-positive (S/P) ratios rose by a mean of 0.95 (95% confidence interval [CI] = 0.64–1.25) and 1.72 (95% CI = 1.55–1.89) in seropositive, non-PI calves and in PI calves, respectively. The mean S/P ratios then declined to approximately 1.1 in non-PI calves and 0.5 in PI calves at between 60 and 80 days of age. In PI calves, testing for antigen in serum and nasal and saliva swabs was subject to interference by colostrum-derived antibodies in calves up to 3 weeks of age. Nasal swabs were less affected than serum and saliva swabs. Ear notches maintained positive ACE corrected optical densities at all s le times, despite a drop in the signal following the ingestion of colostrum.
Publisher: Elsevier BV
Date: 02-2015
Start Date: 2011
End Date: 2013
Funder: Meat and Livestock Australia
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