BHV1 infections: relevance and spread in Europe

A retrospective evaluation of pooled serum ELISA testing in the frame of the French eradication program for infectious bovine rhinotracheitis

Pooled serum testing using whole-virus indirect ELISA has been recently recognized as an official method for surveillance of bovine herpesvirus 1 (BoHV1) in cattle herds in Europe. In this study, a retrospective analysis of data from the French BoHV1 surveillance campaign 2018-2019, including 7434 BoHV1-free certified herds and 157 infected herds, was performed in order to evaluate the diagnostic specificity and sensitivity of two pooled serum indirect ELISAs (from IDEXX and IDVet), in comparison with individual testing by blocking ELISAs targeting the gB and gE proteins. Pooled serum testing showed a relative specificity higher than 97.5% and a detection rate of 100% since all gB+/gE+ samples were found in positive pools. At the herd level, no more than one false positive pool was observed in most of BoHV1-free certified herds, leading to a herd relative specificity of 85.1% and 86.0% for the IDEXX and IDVet pooled serum ELISAs, respectively. Among infected herds tested by pool sizes up to 10 sera (n = 122), 46% of herds were detected through pools of size 10 containing a single positive sample, 23% through pools of size 10 containing at least two positive samples, and 31% through pools of smaller sizes. A complementary study based on manually constituted pools revealed that at least one positive sample in 100% and 93.4% of herds could be detected individually by pools of size 10 with the IDEXX and IDVet ELISAs, respectively. However, pooled serum ELISAs were influenced by the level of individual reactivity, since pools composed of either one weak-positive sample or one gB+/gE- sample could yield negative results. Altogether, these results provided the first evidence that pooled serum testing (pool size up to 10) is a suitable strategy for surveillance of BoHV1-free cattle farms.

Prevalence of Bovine Viral Diarrhoea Virus (BVDV), Bovine Herpes Virus 1 (BHV 1), Leptospirosis and Neosporosis, and associated risk factors in 161 Irish beef herds

BACKGROUND

There are limited data available, in Ireland or elsewhere, to determine the extent of exposure to various endemic diseases among beef cows and factors associated with exposure to causative pathogens. The objectives of this study were to determine the herd and within herd prevalence of Bovine Viral Diarrhoea Virus (BVDV), Bovine Herpes Virus 1 (BHV-1), Leptospirosis and Neosporosis in a large scale study of commercial beef herds on the island of Ireland, and to examine herd level factors associated with exposure to these pathogens in these herds.

RESULTS

The average number of cows tested per herd was 35.5 (median 30). Herd level seroprevalence to Bovine Herpesvirus-1(BHV-1), Bovine Viral-Diarrhoea Virus (BVDV), Leptospirosis and Neosporosis was 90%, 100%, 91% and 67%, respectively, while the mean within herd prevalence for the these pathogens was 40%, 77.7%, 65.7% and 5.7%, respectively. The study confirms that the level of seroconversion for the four pathogens of interest increases with herd size. There was also evidence that exposure to one pathogen may increase the risk of exposure to another pathogen.

CONCLUSIONS

Herd level seroprevalences were in excess of 90% for BVDV, BHV-1 and Leptosporosis. Larger herds were subject to increased exposure to disease pathogens. This study suggests that exposure to several pathogens may be associated with the further exposure to other pathogens.

Prevalence of The Main Infectious Causes of Abortion in Dairy Cattle in Algeria

Introduction

Abortion in cattle is a major source of economic losses for the agriculture sector. It can be due to infectious or non-infectious factors. Among infectious factors, parasites, bacteria, viruses, and fungi can be involved. The present work investigated the prevalence of the main infectious agents of abortion in Algerian cattle.

Material and Methods

Altogether 278 non-aborting and 82 aborting cows were analysed.

Results

The prevalence ranged from 0% for Tritrichomonas foetus to 15% for Neospora caninum. Additionally, a case-control study was performed to find the association between the presence of the pathogens and the occurrence of abortion in cows. The odds ratios were significant for Neospora caninum, bovine herpes virus 4, BVD virus, Brucella abortus, Salmonella Dublin, Leptospira interrogans serovar Hardjo, and Coxiella burnetii.

Conclusions

The pathogens enumerated here could be major causes of abortion among Algerian cattle.

Bovine herpesvirus 1 abortion: current prevalence in the United Kingdom and evidence of hematogenous spread within the fetus in natural cases

While Bovine herpesvirus 1 (BoHV-1) has been known as a cause of bovine abortion for nearly 50 years, information is limited on the current prevalence of BoHV-1 abortion in the United Kingdom, or about the mode of virus dissemination to cause infection of the fetus. The present study aimed to investigate these issues by surveying the prevalence of BoHV-1 in abortion cases in the United Kingdom, and comparing diagnostic methods to determine which are most efficient in BoHV-1-induced abortion. Where BoHV-1 DNA was detected, viral load was compared in fetal tissues, using real-time polymerase chain reaction (PCR), supported by histopathology and immunohistochemistry (IHC) to investigate virus dissemination in bovine abortions. A total of 400 U.K. bovine abortion cases were studied; PCR detected BoHV-1 nucleic acids in 10 cases, suggestive histopathological lesions were observed in 8, and positive IHC staining was observed in 9. In routine diagnosis, BoHV-1 was identified in 2 of these cases, highlighting the utility of using molecular diagnostic tests such as real-time PCR to achieve high sensitivity in potentially autolyzed tissues. The study of different fetal samples showed the highest viral load in the liver, along with severe multifocal necrotic hepatitis, suggesting either a clear tropism of the virus for this organ or that it is the first location to be reached in the fetus. Presence of viral antigen in endothelial cells of the placenta, brain, or heart suggest a hematogenous spread of virus from placenta to the liver, through the umbilical vein, and then to the rest of the organs via fetal blood vessels.

Aspects of bovine herpesvirus-1 infection in dairy and beef herds in the Republic of Ireland

Background

Infection with bovine herpesvirus-1 (BHV-1) causes a wide range of disease manifestations, including respiratory disease and abortion, with world-wide distribution. The primary objective of the present study was to describe aspects of BHV-1 infection and control on Irish farms, including herd-level seroprevalence (based on pooled sera) and vaccine usage.

Methods

The characteristics of a diagnostic indirect BHV-1 antibody ELISA test when used on serum pools were evaluated using laboratory replicates for use in the seroprevalence study. The output from this indirect ELISA was expressed as a percentage positivity (PP) value. A proposed cut off (PCO) PP was applied in a cross-sectional study of a stratified random sample of 1,175 Irish dairy and beef cattle herds in 2009, using serum pools, to estimate herd seroprevalence. The study was observational, based primarily on the analysis of existing samples, and only aggregated results were reported. For these reasons, ethical approval was not required. Bulk milk samples from a subset of 111 dairy herds were analysed using the same ELISA. Information regarding vaccine usage was determined in a telephone survey.

Results

A PCO PP of 7.88% was determined to give 97.1% sensitivity and 100% specificity relative to the use of the ELISA on individual sera giving maximization of the prevalence independent Youden's index, on receiver operating characteristics analysis of replicate results. The herd-level BHV-1 seroprevalence was 74.9% (95% CI - 69.9%-79.8%), with no significant difference between dairy and beef herds. 95.5% agreement in herd classification was found between bulk milk and serum pools. Only 1.8 percent of farmers used BHV-1 marker vaccine, 80% of which was live while 75% of vaccinated herds were dairy.

A significant association was found between herd size (quartiles) and seroprevalence (quartiles).

Conclusions

The results from this study indicate BHV-1 infection is endemic, although BHV-1 vaccines are rarely used, in the cattle population in Ireland.

Cervid herpesvirus 2 causes respiratory and fetal infections in semidomesticated reindeer

Members of the viral subfamily Alphaherpesvirinae establish latency from which they can be reactivated. Bovine herpesvirus 1 causes infectious bovine rhinotracheitis and infectious pustular vulvovaginitis in cattle, as well as abortion and weak calves. Serological evidence of alphaherpesvirus infection has been reported for wild and semidomesticated reindeer (Rangifer tarandus tarandus) in Norway. To address the possibility that reindeer alphaherpesvirus (cervid herpesvirus 2 [CvHV-2]) infection might affect the respiratory system and in part explain the relatively high mortality of reindeer calves during their first year, tissue samples were obtained from reindeer and reindeer fetuses at slaughterhouses in Finnmark County, Norway. A nested pan-alphaherpesvirus PCR amplification targeting the highly conserved UL27 gene (encoding glycoprotein B) was used. Sequencing of amplicons revealed the presence of CvHV-2 DNA. The detection of CvHV-2 DNA in trigeminal ganglia (27 of 143 samples), nasal swabs (5 of 75 samples), and fetal tissues (12 of 48 samples) indicates that CvHV-2 infection is endemic in this reindeer population. Moreover, the virus is transmitted horizontally by the respiratory route, establishing latency in the trigeminal ganglion, and vertically to the fetus through the placenta. Further studies should focus on the reproductive impact of CvHV-2 infection in reindeer.

Validation of a real-time PCR assay for the detection of bovine herpesvirus 1 in bovine semen

A real-time polymerase chain reaction (PCR) assay was developed for detection of the presence of bovine herpesvirus type 1 (BoHV-1) in extended bovine semen. The assay detects a region encoding a highly conserved glycoprotein B gene. The real-time PCR assay was validated for specificity, sensitivity and repeatability using spiked semen and semen from naturally infected animals. The real-time PCR was very rapid, highly repeatable and more sensitive (lower detection limits) than conventional virus isolation method for the detection of BoHV-1 in extended semen. The specificity of the assay is as expected. The assay had an analytical sensitivity of 0.38 TCID(50) virus spiked into negative semen. The second real-time PCR system for the detection of the bovine growth hormone (bGH) gene was applied as an internal control for the DNA extraction and PCR. The bGH PCR can be performed separately to BoHV-1 PCR, or in a duplex format. The real-time PCR assay is intended for use in international trade. The complete validation dossier based on this study and an international inter-laboratory ring trial has been accredited by the Office International des Epizooties (OIE) and has been recommended to be adopted as a prescribed test for international trade.

Relative efficacy of inactivated bovine herpesvirus-1 (BHV-1) vaccines

The relative efficacy of four commercially available inactivated bovine herpesvirus-1 (BHV-1) vaccines was directly assessed in controlled studies in 5-6-month-old, BHV-1 naïve calves. The sero-response due to the basic course of two intramuscular vaccinations was closely similar for three of four vaccines whereas one vaccine did not induce seroconversion in five of six calves. At the level of challenge virus shedding in nasal mucus, all four vaccines were significantly protective but to a markedly variable degree. Clinically, however, the relative protection ranking of the vaccines was different to that observed for challenge virus shedding. There was no obvious correlation observed between pre-challenge circulating virus neutralising antibody titre and vaccine-induced protection against virus shedding or clinical signs following the intranasal BHV-1 challenge. Present comparative findings suggest that commercially available BHV-1 vaccines are likely to be of variable potency in the natural host.

Characteristics of live bovine herpesvirus-1 vaccines

The common disease caused by bovine herpes virus 1 infection is febrile rhinotracheitis (FRT) and under certain conditions the virus is strongly implicated in pre-disposing cattle to pneumonic pasteurellosis. These illnesses account for a significant economic loss in the cattle industry worldwide and vaccination is widely applied. In naive cattle, and for a short period of time, old and new vaccines significantly reduce clinical signs of FRT and also virus shedding. A single intranasal vaccination affords significant protection in face of maternally derived antibodies, and the protection can be significantly prolonged by a booster intramuscular vaccination. Current data recommend vaccination in face of an outbreak and vaccines appear safe for pregnant cattle.

Viral diseases of the ruminant nervous system

This article presents the etiology, epidemiology, clinical features,and diagnosis of the primary viral neurologic diseases observed in ruminants. In general, these viral neurologic diseases are uncommon but often fatal. Rabies virus is perhaps the most important cause of encephalitis in cattle because of the public health implications. Other viral encephalitis diseases in ruminants include bovine herpesvirus encephalomyelitis, pseudorabies, malignant catarrhal fever, ovine and caprine lentiviral encephalitis, West Nile virus encephalitis, Borna disease, paramyxoviral sporadic bovine encephalomyelitis,and ovine encephalomyelitis (louping-ill).

Subclinical breakdown with infectious bovine rhinotracheitis virus infection in dairy herd of high health status

Infectious bovine rhinotracheitis (IBR) virus infection was detected by an antibody ELISA in the bulk milk of a large closed dairy herd of high health status in an area of low cattle density in East Anglia. The herd was managed under high standards of biosecurity and was known to have been serologically free of IBR virus for the previous 13 years. Although over 70 per cent of the cows had seroconverted to IBR virus no clinical signs were observed apart from a slight bilateral watery ocular discharge in a few cows, and their performance and productivity were unaffected. The causal virus, which was isolated after it had been reactivated with corticosteroid, had the DNA profile of a bovine herpesvirus type 1 strain normally associated with clinically severe respiratory disease. In spite of extensive enquiries and seroepidemiological investigations the source of the infection was not determined.

Viral infections and bovine mastitis: a review

This review deals with the role of viruses in the aetiology of bovine mastitis. Bovine herpesvirus 1, bovine herpesvirus 4, foot-and-mouth disease virus, and parainfluenza 3 virus have been isolated from milk from cows with clinical mastitis. Intramammary inoculations of bovine herpesvirus 1 or parainfluenza 3 virus-induced clinical mastitis, while an intramammary inoculation of foot-and-mouth disease virus resulted in necrosis of the mammary gland. Subclinical mastitis has been induced after a simultaneous intramammary and intranasal inoculation of lactating cows with bovine herpesvirus 4. Bovine leukaemia virus has been detected in mammary tissue of cows with subclinical mastitis, but whether this virus was able to induce bovine mastitis has not been reported. Bovine herpesvirus 2, vaccinia, cowpox, pseudocowpox, vesicular stomatitis, foot-and-mouth disease viruses, and bovine papillomaviruses can play an indirect role in the aetiology of bovine mastitis. These viruses can induce teat lesions, for instance in the ductus papillaris, which result in a reduction of the natural defence mechanisms of the udder and indirectly in bovine mastitis due to bacterial pathogens. Bovine herpesvirus 1, bovine viral diarrhoea virus, bovine immunodeficiency virus, and bovine leukaemia virus infections may play an indirect role in bovine mastitis, due to their immunosuppressive properties. But, more research is warranted to underline their indirect role in bovine mastitis. We conclude that viral infections can play a direct or indirect role in the aetiology of bovine mastitis; therefore, their importance in the aetiology of bovine mastitis and their economical impact needs further attention.

Probability of and risk factors for introduction of infectious diseases into Dutch SPF dairy farms: a cohort study

A 2-year cohort study was conducted to investigate the probability of disease introduction into Dutch dairy farms. The farms were tested regularly for diseases and were visited biannually to collect management data. Ninety-five specific pathogen-free (SPF) dairy farms were selected from a database of bovine herpesvirus type 1 (BHV1)-free farms to study the probability of, and risk factors for, introduction of BHV1, bovine viral diarrhoea virus (BVDV), Salmonella enterica subsp. enterica serotype Dublin (S. dublin), and Leptospira interrogans serovar hardjo (L. hardjo). Although most of the 95 SPF farms had a low risk on introduction of infectious diseases, one disease was introduced into 12 farms and two diseases were introduced into one farm. Three farms experienced an outbreak of BHV1, one farm an outbreak of L. hardjo, two farms BVDV, six farms S. dublin, and one farm both BHV1 and S. dublin. The total incidence rate was 0.09 (0.06-0.12) per herd-year at risk. The results suggest that the "non-outbreak" farms were significantly more closed than the "outbreak" farms. Direct animal contacts with other cattle should be avoided and professional visitors should be instructed to wear protective clothing before handling cattle.

A rapid and sensitive PCR-based diagnostic assay to detect bovine herpesvirus 1 in routine diagnostic submissions

We describe a rapid, sensitive and specific polymerase chain reaction (PCR) assay for the detection of BHV1 DNA in a range of routine diagnostic submissions without the need for prior virus isolation. The assay, which is based on the selected amplification of a portion of the viral tk gene, detected both BHV1.1 and BHV1.2 subtypes in a panel of 15 characterised field isolates, and its sensitivity was estimated to be <0.125 TCID(50). BHV2, alcephaline herpesvirus, BHV4, equine herpesvirus 1 (EHV1), EHV4 and pseudorabies virus were not detected confirming the specificity of the assay. One hundred and five diagnostic submissions, including tissues, nasal secretions and nasal swabs were taken from cattle with respiratory disease and tested using the routine methods of virus isolation (VI) and the fluorescent antibody test (FAT), and the results were compared with those obtained by PCR. The PCR assay detected BHV1 DNA in all samples that were positive by VI. BHV1 DNA was also detectable by PCR in raw and extended semen samples at a sensitivity of 1 TCID(50) per 50microl. The assay also detected BHV5, permitting differentiation between it and BHV1 by virtue of the size of the amplified PCR product. The PCR assay is more sensitive and independent of sample quality than either virus isolation or FAT, and it is faster than virus isolation. The sample preparation method is simple with few steps involved. There are no extra post-amplification blotting/hybridisation steps and the assay is not based on a nested PCR strategy that might otherwise exacerbate the problem of oversensitivity/contamination in the routine use of such a test in a diagnostic laboratory. This assay would permit discrimination between those animals naturally infected with wild type BHV1 and those vaccinated with tk-BHV1 strains.

Erradicação do herpesvírus bovino - 1 (BHV-1) de um rebanho bovino leiteiro em manejo semi-intensivo

Com o objetivo de erradicar o BHV-1 de um rebanho bovino leiteiro de alto valor genético sem a utilização de vacina, foi realizado um exame sorológico prévio em 154 animais, onde constatou-se 15,6% de reagentes ao BHV-1. A técnica utilizada foi a soroneutralização em microplacas. Dentre os animais soropositivos, as vacas vazias foram descartadas imediatamente e as prenhes isoladas e descartadas após o parto. Os bezerros apresentaram anticorpos colostrais até os seis meses de idade, motivo pelo qual não foram descartados; nos bezerros de 6 a 12 meses de idade e nas novilhas não foram diagnosticados animais soropositivos. Os animais foram examinados trimestralmente, por 21 meses, seguido de mais duas coletas semestrais. As vacas secas, prenhes e em lactação, soropositivas, revelaram ser a fonte de infecção do BHV-1. A manutenção de rebanho livre é possível, desde que sejam adotadas medidas como a utilização de sêmen livre de BHV-1, realização de quarentena no ingresso de animais e exames sorológicos anuais visando impedir a reintrodução do vírus. Com o conjunto destas medidas adotadas, a fazenda encontra-se há 18 meses livre do BHV-1.

Rapid detection of bovine herpesvirus 1 in the semen of infected bulls by a nested polymerase chain reaction assay

A nested polymerase chain reaction (PCR) assay was developed for the detection of bovine herpesvirus 1 (BHV-1) in bovine semen and compared with the virus isolation method. When extended semen, commonly used in the bovine artificial insemination industry, was inoculated with BHV-1, the PCR assay detected BHV-1 DNA in semen inoculated at 0.25-2.5 TCID50 per 0.5 mL. In contrast, the lower limit of detection for virus isolation was 250 TCID50 of BHV-1 inoculated in 0.5 mL of extended semen. These methods were also used to detect BHV-1 in the semen of four bulls which were experimentally infected with BHV-1. All infected bulls demonstrated balanitis at 3 d post-inoculation (DPI) and severe balanoposthitis at 4 DPI. BHV-1 was detected in raw semen by virus isolation and PCR at 2 DPI, before balanitis was evident. For virus isolation, the last day that BHV-1 was detected during primary infection was 7 DPI for two bulls and 9 and 11 DPI for the other two bulls. In contrast, PCR detected BHV-1 in the bulls' semen until 14 or 18 DPI. For individual animals, PCR detected BHV-1 during primary infection for at least 1-10 d longer than virus isolation. Reactivation of BHV-1 from latency without the presence of visible lesions was promoted twice by two series of 5 d dexamethasone injections. For the first series of dexamethasone treatments, a positive virus isolation result was obtained on the 5th d of treatment for only one bull. In contrast, two bulls demonstrated evidence of viral reactivation on this day by PCR. All bulls shed BHV-1 in semen on d 4 after dexamethasone treatment, as evidenced by positive virus isolation and PCR results. One bull was still PCR positive 13 d later. For the second series of dexamethasone treatments, a small amount of virus was isolated from semen collected on d 3 or 4 after treatment for two bulls but not from the other two bulls. In contrast, semen samples from all bulls were PCR positive for either or both of these 2 d. In total, from 80 semen samples, 45 were PCR positive and 26 were virus isolation positive. Thus, the PCR assay detected BHV-1 shedding in bulls earlier, more often, and for a longer duration, than did the virus isolation method.

Bovine herpesvirus meningoencephalitis association with infectious bovine rhinotracheitis (IBR) vaccine

During 1992, on a farm in the Tokachi district of Hokkaido, Japan, approximately 20 Holstein-Friesian calves showed neuroparalysis and died within 7-10 days after routine vaccination. Six male calves, aged about 1.5 months, were submitted to our laboratory for pathological examination and diagnosed as acute or subacute necrotizing meningoencephalitis due to bovine herpes virus (BHV) infection. The main necropsy findings included a few hemorrhages or clots, and malacic lesions localized in the cortical to subcortical area of the cerebrum. Histopathological brain lesions were characterized by laminar or focal necrosis of neurons, accompanying macrophages, polymorphonuclear cell infiltration, severe astrogliosis, and perivascular cuffing in all six calves. Nuclear basophilic inclusion bodies, which showed positive reaction with immunocytochemical staining of BHV antigen, were observed in the necrotic neurons, astroglia and oligodendroglia in five affected calves. BHV antigens were also seen in the cell bodies and cell processes of the necrotic neurons, which was indicative of cell-to-cell propagation of infection. There was a general tendency for more severe lesions to be located at the cortex to subcortex of the cerebrum. Milder lesions were observed in the cerebellum and brain stem. These findings suggest that the infectious route to the cerebrum in the present cases was through the olfactory bulbs and/or along the meninges beginning from the ethmoid bone, rather than through the trigeminal ganglia route as had been emphasized in studies dealing with experimental infection.

Detection of bovine herpesvirus 1 in the semen of experimentally infected bulls by dot-blot hybridisation, polymerase chain reaction and virus isolation

Two 18-month-old bovine herpesvirus 1 (BHV1)-seronegative bulls were inoculated experimentally with BHV1 via their prepuces. Semen collected at intervals was examined by optimised virus isolation, dot-blot hybridisation and the polymerase chain reaction (PCR) for detection of BHV1, and the infection was monitored serologically by using a virus neutralisation test. Antibodies were first detected 10 days after inoculation and were still present 40 days after inoculation. Semen collected from four to 40 days after inoculation was positive by PCR with Southern blot hybridisation whereas only the semen collected on day 4 was positive by dot-blot hybridisation, virus isolation and PCR with ethidium bromide staining. These results indicate that the bulls started to shed the virus in semen before they developed any detectable antibody. PCR with Southern blot hybridisation was the most sensitive of the three methods and detected virus for the longest period.

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.

Detection of bovine herpesvirus-1 in bovine semen by a nested PCR assay

A nested PCR assay targeting a portion of the glycoprotein IV gene has been developed for the detection of Bovine Herpesvirus-1 (BHV-1). Rapid and sensitive detection of the PCR products was achieved using a nonisotopic reverse dot-blot format with a visible color readout. Cross-reactivity of this PCR assay was not observed with the closely related BHV-3. The sensitivity of this assay when tested on a supernatant from a BHV-1 cell culture was approximately 4.5 TCID50 (50% tissue culture infectious dose). A procedure using the chelating resin Chelex 100 was used to prepare viral DNA from artificially inoculated samples of extended and raw semen for use in the PCR assay. In combination with nested PCR and reverse dot blot, this method allowed the detection of 5 x 10(3) TCID per 0.5 ml of semen, which is comparable to the detection in the Cornell Semen Test. The whole procedure can be completed in approximately 8 h. This assay has therefore the potential of replacing the currently available yet time consuming and costly detection methods for BHV-1 in bovine semen.

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

Sixteen commercial or non-commercial enzyme-linked immunosorbent assays (ELISAs) for bovine herpesvirus 1 (BHV1)-specific antibody detection in serum were compared using 41 bovine sera of well defined origin. All ELISAs were able to detect correctly most of the antibody negative sera (specificity > or = 92%). The ability, however, to detect specific antibodies varied considerably between ELISAs. Sensitivity, estimated by testing 18 positive sera, ranged between 50% and 100%. Sera with titers of at least 64, as measured by the 24 h virus neutralisation test, were identified as being positive by all ELISAs. Most assays were unable to detect specific IgM antibodies present in sera collected 9 days after experimental infection. Only one assay, an indirect ELISA using undiluted test serum, showed a sensitivity of 100%. This ELISA was found to be 8 times more sensitive than the 24 h neutralisation test and had the unique property of showing a weak consistently positive response with some sera collected from breeding bulls. The findings of this study indicate the need for international standardisation of tests to detect BHV1-specific antibodies in cattle.