Comparative study on sixteen enzyme-linked immunosorbent assays for the detection of antibodies to bovine herpesvirus 1 in cattle

Sero-diagnostic efficacy of various ELISA kits for diagnosis of infectious bovine rhinotracheitis (IBR) in cattle and buffaloes in India

Bovine alphaherpesvirus-1 (BoHV-1), the causative agent of infectious bovine rhinotracheitis (IBR), is an economically important viral pathogen affecting cattle and buffaloes. Serological assays are mostly used for detection of the antibodies, but variation has been detected in the diagnostic performances of the individual assay. In the present study, four commercially available ELISA kits {two indirect ELISA (kits A and B) and two blocking ELISA (kits C and D)} were evaluated for the detection of antibodies against BoHV-1 in Indian cattle and buffaloes (fitness of purpose). The diagnostic sensitivity (dsn) and specificity (dsp) of these kits were determined by three ways; considering virus neutralization test (VNT) as gold standard test, using pre-test information of the samples, and majority of tests. Screening of 200 known negative sera (124 cattle, 76 buffaloes) sourced from IBR free farms revealed gB based ELISA kits are more specific than the indirect ELISA kits. Testing of 125 known positive sera (81 cattle, 44 buffaloes) suggests kit B be most sensitive followed by kit C, A and D. Interestingly, kit D was found to be most sensitive for detection of vaccination-induced BoHV-1 antibodies followed by kit B. Similar trend were also observed in the limit of dilution experiment performed using known infected and vaccinated sera. VNT was found to be the most specific test and its use as the gold standard test revealed all kits to have more than 99 % sensitivity. All the ELISA kits could detect BoHV-1 specific antibodies in the IBR vaccinated calves as early as 11 days post-vaccination. In Kappa statistics, an almost perfect agreement between the ELISA kits was recorded. The overall performance of the kits in serodiagnosis of IBR as determined by the area under curve in ROC analysis was good.

Neutralizing antibodies to bovine herpesvirus types 1 (BoHV-1) and 5 (BoHV-5) and its subtypes

This study was carried out to determine whether the sensitivity of serum neutralization (SN) tests would be affected by the use of distinct subtypes of bovine herpesvirus 1 (BoHV-1) and 5 (BoHV-5) as test challenge viruses. Bovine sera collected from a randomized sample (n=287) were tested in a 24h incubation SN against three type 1 viruses (BoHV-1.1 strains "Los Angeles" (LA) and "EVI 123"; BoHV-1.2a strain "SV 265") and three type 5 viruses (BoHV-5a strain "EVI 88"; BoHV-5b strain "A 663" and BoHV-5c "ISO 97"). SN sensitivity varied greatly depending on the test challenge virus used in the test, particularly when results against each virus were considered individually, where it ranged from 77% (detecting 80 out of 104 antibody-positive sera) with ISO 97 to 91% (95/104) with BoHV-1.1 strain LA. All tests to single viruses revealed a significantly low sensitivity (McNemar's; p<0.05). Maximum sensitivity (104/104) was achieved when positive results to a particular combination of four of the challenge viruses (LA+EVI 123+SV 265+A 663) or some combinations of five viruses (or all six viruses) were added cumulatively. These results provide evidence for no association between any particular virus type/subtype and higher SN sensitivity. In addition, it was clearly shown that when SN is performed with single test challenge viruses, sensitivity can vary so significantly that might compromise control or eradication efforts. Performing SN against a number of different viruses demonstrated to improve significantly the test's sensitivity.

A retrospective analysis of the infectious bovine rhinotracheitis (bovine herpes virus-1) surveillance program in Norway using Monte Carlo simulation models

Serological surveillance for antibodies against bovine herpes virus type I (BHV-1) which causes infectious bovine rhinotracheitis and infectious pustular vulvovaginitis has been carried out since 1992 in Norway. Since 1993 (when a single infected herd was detected) all bulk-milk and pooled-serum samples have been negative for BHV-1 antibodies. This paper describes the use of Monte Carlo simulation models for the analysis and interpretation of the results of the surveillance and provides support for the contention that the Norwegian cattle population is not infected by BHV-1.

The serological BHV1 status of dams determines the precolostral status of their calves

Precolostral calves and their dams were serologically investigated for the presence of antibodies against Bovine Herpesvirus 1 in diagnostic tests with a very high sensitivity and specificity. Although the syndesmo-chorial type of placenta of ruminants does not transfer gamma globulins, a large number of calves had antibodies, in most cases in a very low concentration. Significant correlations were found between the serological status of the dam, the status of the calf, and the titre of antibodies. Oral intake of maternal blood by the calf at birth or transmission or leakage of maternal antibodies during pregnancy might be possible causes of precolostrally positive calves. From the results it is concluded that to reduce the risk of obtaining BHV1-positive calves, BHV1-negative dams should be selected for breeding purposes.

A comparative study of serological tests for use in the bovine herpesvirus 1 eradication programme in The Netherlands

We compared a gB-ELISA, a gE-ELISA and a Danish test system (consisting of a blocking and an indirect ELISA) for their specificity and sensitivity to detect antibodies against BHV1. The Danish test system showed the highest sensitivity and the gE-ELISA the lowest; the gB-ELISA showed an intermediate sensitivity. If the doubtful zone (25-50% blocking) of the gB-ELISA was considered as positive (gB-ELISA+), the sensitivity almost reached that of the Danish test system. The specificity of all tests appeared to be very high, 99.7, 96.7, 100, 99.7% for the gB-ELISA, gB-ELISA+, gE-ELISA and the Danish test system, respectively. Seroconversion was detected in the gE-ELISA up to 3 weeks later than in the gB-ELISA and the Danish test system. It is concluded that the combination of a gB-ELISA (for screening) and the Danish test (for confirmation) system used in the BHV1 eradication programme in the Netherlands, provides for very high sensitivity (> 99.0%) (Kramps et al., 1994) and a very high specificity (> 99.9%).

A simple, specific, and highly sensitive blocking enzyme-linked immunosorbent assay for detection of antibodies to bovine herpesvirus 1

By using a monoclonal antibody directed against an epitope located on glycoprotein B of bovine herpesvirus 1 (BHV1), a simple, convenient blocking enzyme-linked immunosorbent assay (ELISA) which combines a high sensitivity with a low false-positive rate has been developed. The test can be performed at low variance on undiluted bovine serum samples. The epitope on glycoprotein B appears to be conserved, because it could be detected by immunostaining in all of 160 BHV1 isolates originating from 10 countries. In testing 215 anti-BHV1 antibody-negative and 179 anti-BHV1 antibody-positive serum samples, specificity and sensitivity were 0.96 and 0.99, respectively. This blocking ELISA is superior to a commercially available indirect ELISA and to the 24-h virus neutralization test in detecting low antibody levels in serum. In addition, this blocking ELISA is able to detect specific antibodies in serum as early as 7 days postinfection. To minimize any risk of introducing latent BHV1 carriers among noninfected cattle, this blocking ELISA would be, in our opinion, the test of choice.