The effect of natural and artificial breeding using bulls infected with, or semen contaminated with, infectious bovine rhinotracheitis virus

Bovine alphaherpesvirus 1 (BHV1) infection in testes and epididymis from bulls from a slaughterhouse

Bovine alphaherpesvirus 1 (BHV1) is an agent associated with reproductive disease in cattle. Viral pathogenicity is related to disorders such as temporary infertility, embryonic death, and abortions in affected animals. Considering that natural infections in genital organs of males are understudied, this investigation evaluated the presence of BHV1 in both testicular and epididymal tissues obtained from naturally infected bulls by the evaluation of the presence of the BHV1 genome and antigens. Sixty samples of blood and genital organs of 60 bulls that were not vaccinated against BHV1 were assayed. Fragments from testes and head, body, and tail of epididymides were processed and analyzed by nested PCR and immunofluorescence with confocal laser scanning microscopy. Also, the BHV1 gB glycoprotein gene of 14 positive samples was partially sequenced. The percentage of BHV1 presence obtained by the immunolocalization assay corresponded to 95.9% of the testes, 100% of the epidydimal tissue in the head and tail portions, and 98% of the epididymal body. The nested PCR assay detected the viral nucleic acid in 59.2% of the testicular tissue and in 65.3, 75.5, and 83.7% of epididymis head, body, and tail samples, respectively. The partial sequences analyzed presented 100% of identity with other BHV1 strains. Accordingly, BHV1 detection in testes and epididymides of naturally infected bulls suggests that these organs may be sources of viral infection for semen.

Detection of bovine herpesvirus 1 in genital organs of naturally infected cows

Bovine herpesvirus 1 (BoHV-1) is a causative agent of respiratory diseases in cattle, and infection with BoHV-1 can cause reproductive failure. There are few studies regarding infections in natural conditions in the reproductive organs of bovine animals. In this context, this study investigated the presence of BoHV-1 in the uterus, oviducts, and ovarian tissues of naturally infected cows. The three genital structures were evaluated for the presence or absence of BoHV-1 by immunofluorescence assay using confocal scanning laser microscopy. Blood and genital organ samples of 75 cows unvaccinated against BoHV-1 were used. Fragments of uterus, oviduct, and ovarian tissue were processed and analyzed by confocal scanning laser microscopy. Neutralization by antibodies was observed in 54.7% (41/75) of the serum samples tested. BoHV-1 were detected in the uterus of all the seropositive cows. The oviducts contained BoHV-1 in 73.2% of the samples and the ovaries contained BoHV-1 in 58.5% of the samples from seropositive animals. The presence of the virus was not observed in any of the genital organs of seronegative animals. There was no correlation between the antibody titer and the detection of BoHV-1 in positive tissue in the different genital organs or with the number of infected structures per animal. The detection of BoHV-1 in 100% of the uterus samples from seropositive cows suggests that this organ may be a source of infection for the fetus, resulting in abortion. Further studies on the mechanism by which BoHV-1 infects the fetus via the uterine route should be performed.

Infectious reproductive disease pathogens in dairy herd bulls

OBJECTIVE

Investigate the presence of infectious reproductive disease pathogens in dairy herd bulls in south-west Victoria, Australia, using a cross-sectional study.

METHODS

Dairy herd bulls from 32 herds were sampled for bovine viral diarrhoea virus (BVDV: 256 bulls, 32 herds) prior to the natural mating period, bovine herpes virus-1 prior to (10 bulls, 5 herds) and after (118 bulls, 19 herds) the natural mating period, and for Campylobacter fetus spp. and Tritrichomonas foetus after the natural mating period (61 bulls, 7 herds). BVDV was detected from an ear-notch sample using a commercially available rapid assay ELISA, bovine herpes virus-1 and T. foetus were screened for by PCR from a penile swab and preputial sample respectively, and C. fetus spp. were screened for by culture of preputial samples.

RESULTS

None of the bulls tested positive for BVDV antigen. Campylobacter fetus venerealis (or C. fetus fetus) was cultured in 6.6% (4/61) of bulls, representing 2 of the 7 (28.6%) farms that were not vaccinating bulls against bovine genital campylobacteriosis. Bovine herpes virus-1 was identified in 7.8% (10/128) bulls sampled; T. foetus was not identified in any samples.

CONCLUSION

Bovine genital campylobacteriosis is present in south-western Victoria, despite longstanding recommendations to vaccinate bulls. Screening bulls for persistent infection with BVDV is probably justified, despite the absence of persistently infected bulls in this study. Further research is warranted to investigate the potential reproductive implications of BHV-1, and the presence of T. foetus.

Bovine herpes virus-1 (BoHV-1) in cattle-a review with emphasis on reproductive impacts and the emergence of infection in Ireland and the United Kingdom

Bovine reproductive disease attributable to bovine herpes virus-1 (BoHV-1) was first described in Germany in the 19th century, being recognised primarily as the cause of infectious vulvovaginitis and balanoposthitis until the mid-1950s when a more virulent strain of the virus (BoHV-1.1) associated with respiratory disease (infectious bovine rhinotracheitis; IBR) emerged in the western United States. Subsequently, IBR emerged as a clinical condition in Europe, from the 1970s onward. While the ability of BoHV-1 to produce respiratory disease is now well recognised, the potential negative outcomes of infection on fertility and reproduction are less frequently considered. This review was conducted against the background of the prioritization of disease caused by BoHV-1 as one of several diseases to be addressed by Animal Health Ireland, with the twin goals of summarizing the published literature on the potential outcomes of infection at different stages of breeding and pregnancy, and of describing the emergence of BoHV-1 as a significant pathogen in Ireland and the UK.

Inactivation of bovine herpesvirus-1 (BHV-I) from in vitro infected bovine semen

Frozen-thawed bovine semen, experimentally infected with bovine herpesvirus-1 (BHV-1) at levels of 10(3) TCID(50)/ml and 10(4) TCID(50)/ml, was treated with a 0.3% trypsin solution to determine the effect of trypsin on the virus and on fertilization using superovulated animals. Virus was not isolated from any trypsin-treated samples using a cell culture assay system. Nor did two calves develop antibodies to BHV-1 following inoculation with trypsin-treated semen pooled from six bulls. Nonsurgical flushing of eight heifers inseminated with trypsin-treated frozen-thawed semen yielded 28 transferable-quality embryos.

Development of a set of multiplex standard polymerase chain reaction assays for the identification of infectious agents from aborted bovine clinical samples

The current study describes the development of a set of 5 multiplex polymerase chain reaction (mPCR) assays for the simultaneous detection of abortive infection agents in bovine fetal tissues, including Brucella spp., Leptospira spp., and Campylobacter fetus (mPCR1); Hammondia heydorni, Neospora caninum, and Toxoplasma gondii (mPCR2); Coxiella burnetii and Chlamydophila psittaci (mPCR3); Mycoplasma bovis, Mycoplasma bovigenitalium, and Ureaplasma diversum (mPCR4); and Bovine viral diarrhea virus (BVDV) and Bovine herpesvirus-1 (BoHV-1; mPCR5). The protocol was tested on different tissue samples collected from 50 aborted bovine fetuses, and it showed that out of the 50 fetuses, 7 (14%, mPCR2) were PCR-positive for N. caninum, 4 (8%, mPCR5) were PCR-positive for BVDV, and 2 (4%, mPCR4) were PCR-positive for U. diversum. The results obtained by using each multiplex PCR were 100% concordant with those obtained by using the respective PCR assays targeting single genes on the same specimens. Moreover, all multiplex PCR assays on clinical samples were compared with reference methods, obtaining a perfect accordance in all samples and confirming the validity of the set of multiplex PCR assays. The proposed set of multiplex PCR assays is, therefore, suitable for the simultaneous detection of the main infectious agents responsible for bovine abortion.

Infectious causes of reproductive disorders in cattle

The incidences of reproductive disorders in bovine are increasing over years. This scenario is further aggravating due to more emphasis on selection and rearing of animal for specific commercial purposes which compromises livestock reproduction. Reproductive disorders like infertility and abortions in cattle are major problems in the bovine industry. The reproductive disorders might be caused by several different agents such as physical agents, chemical agents, biological agents, etc. Also, the causative agent and pathogenesis of reproductive disorders are influenced by various factors including environmental factor. The exact causes may not be evident and are often complicated with multiple causative agents. Thus, there is a need for multi-faceted approach to understand correlation of various factors with reproductive performance. Of the agents, infectious biological agents are significant cause of reproductive disorder and are of high priority in the bovine industry. These factors are not only related to the prosperity of bovine industry but are also important from public health point of view because of their zoonotic potentials. Several infectious agents like bacterial, viral, protozoon, chlamydial and fungal agents are known to have direct impact on reproductive health of cattle. These diseases can be arranged and discussed in different groups based on the causative agents.

The search for viruses in bovine semen, a review

Viruses reported in bovine semen include those of foot and mouth disease, bluetongue, bovine leukemia, infectious bovine rhinotracheitis, bovine viral diarrhea, ephemeral fever, and lumpyskin disease. Bovine enteroviruses, a parapoxvirus (paravaccinia), and several uncharacterized viruses have also been isolated. Their presence in semen has been recognized by a variety of animal inoculation and cell culture techniques. The prevalence of viruses in semen and the attendant impact on fertility is largely unknown. The widespread distribution of frozen semen, an ideal system for preserving viral infectivity, indicates this product could serve as an important vehicle for transmission of viruses to uninfected herds or areas. This concern has placed restrictions on international movement of semen. Improved methods for detecting viruses in semen are necessary to assess the importance of the problem and to develop realistic precautionary measures.

Bovine herpes virus infections in cattle

Bovine herpes virus 1 (BHV-1) is primarily associated with clinical syndromes such as rhinotracheitis, pustular vulvovaginitis and balanoposthitis, abortion, infertility, conjunctivitis and encephalitis in bovine species. The main sources of infection are the nasal exudates and the respiratory droplets, genital secretions, semen, fetal fluids and tissues. The BHV-1 virus can become latent following a primary infection with a field isolate or vaccination with an attenuated strain. The viral genomic DNA has been demonstrated in the sensory ganglia of the trigeminal nerve in infectious bovine rhinotracheitis (IBR) and in sacral spinal ganglia in pustular vulvovaginitis and balanoposthitis cases. BHV-1 infections can be diagnosed by detection of virus or virus components and antibody by serological tests or by detection of genomic DNA by polymerase chain reaction (PCR), nucleic acid hybridization and sequencing. Inactivated vaccines and modified live virus vaccines are used for prevention of BHV-1 infections in cattle; subunit vaccines and marker vaccines are under investigation.

Evaluation of risks of viral transmission to recipients of bovine embryos arising from fertilisation with virus-infected semen

This scientific review was prompted by recent legislation to curtail the use of semen from potentially virus-infected bulls to produce embryos for import into the European Union. From studies in laboratory animals, humans and horses, it is apparent that viruses may sometimes attach to, or be integrated into, spermatozoa, although in domestic livestock, including cattle, this seems to be a rare phenomenon, and carriage of virus through the zona pellucida into the oocyte by fertilising sperm has never been described in these species. Four specific viruses; enzootic bovine leukosis (EBLV), bovine herpesvirus-1 (BoHV-1), bovine viral diarrhoea virus (BVDV) and bluetongue virus (BTV), all of which tend to cause subclinical infections in cattle, but which can occur in bovine semen, are examined with regard to the risks that use of infected semen might lead to production of infected embryos. With regard to in vivo-derived embryos, when internationally approved embryo processing protocols are used, the risks from EBLV- and BTV-infected semen are negligible, and the same is almost certainly true for semen infected with BoHV-1 if the embryos are also treated with trypsin. For BVDV, there is insufficient data on how the virus is carried in semen and how different BVDV strains can interact with sperm, oocytes and embryos. There is a potential, at least, that in vivo-derived embryos resulting from infected semen might carry BVDV, although field studies so far suggest that this is very unlikely. With regard to in vitro-produced embryos, use of semen infected with any of the four viruses, with the probable exception of EBLV, will often lead to contaminated embryos, and virus removal from these embryos is difficult even when the internationally approved embryo processing protocols are used. However, it has never been demonstrated that such embryos have resulted in transmission of infection to recipients or offspring.

Intrapreputial infection of young bulls with bovine herpesvirus type 1.2 (BHV-1.2): acute balanoposthitis, latent infection and detection of viral DNA in regional neural and non-neural tissues 50 days after experimental reactivation

Venereal infection of bulls with bovine herpesvirus type 1.2 (BHV-1.2) may result in acute balanoposthitis followed by the establishment of latent infection, presumably in dorsal root nerve ganglia. We herein report the characterization of the acute and latent infection of young bulls with a Brazilian BHV-1.2 isolate and the investigation of neural and non-neural sites in which viral DNA persists during latent infection, i.e. 110 days after inoculation and 50 days after experimental reactivation. Intrapreputial inoculation of BHV-1.2 isolate SV-56/90 (10(6.5)pfu per animal) resulted in severe balanoposthitis, characterized by redness of the penis and preputial mucosa, coalescent vesicles and fibrinous exsudate in all four infected bulls. Virus shedding was detected in preputial secretions and semen up to days 14 and 13 pi, respectively. Dexamethasone administration at day 60 pi led to reactivation of the infection in all animals, resulting in virus shedding in preputial secretions and/or in semen. At day 50 post-reactivation (pr), the animals were euthanized and regional tissues were collected for PCR and virus isolation. Viral DNA was consistently detected in the dorsal root ganglia of nerves genito-femoral (4/4) and obturator (4/4); frequently in the pudendal (3/4), sciatic (3/4) and rectal caudal nerve ganglia (2/3). In addition, viral DNA was detected in the pelvic sympathetic plexus of one bull and in regional lymph nodes (deep inguinal (2/4); sacral (1/4); medial iliac (1/4)) of two bulls. No infectious virus could be recovered from homogenates of DNA positive tissues, indicating the absence of actively replicating virus. These results demonstrate that BHV-1.2 DNA may persist in several sacral nerve ganglia and in regional lymph nodes as well during latent infection, i.e. 50 days after experimental reactivation. These findings may help in understanding the pathogenesis of acute and latent genital infection by BHV-1.2.

Bovine herpesvirus 5 (BoHV-5) in bull semen: amplification and sequence analysis of the US4 gene

Bovine herpesvirus type 5 (BoHV-5), which is potentially neuropathogenic, was detected in clinical samples of bovine semen, both directly and after isolation in cell culture, using a nested PCR system for amplifying the US4 gene. Nucleotide sequences generated from the amplicons were analysed and deposited at GenBank (NCBI, Bethesda, MD, USA) under the accession numbers AF298174 and AF330157. Alignment of these sequences and previously deposited sequences of BoHV-1 and BoHV-5 showed 82% and 98% similarity, respectively. The bulls, which were maintained at an artificial insemination centre, had presented no clinical signs, indicating that bovine semen should be screened for BoHV-5 to prevent transmission of the virus.

Effects of bovine herpesvirus type 1 infection in calves with maternal antibodies on immune response and virus latency

The presence of maternally derived antibodies can interfere with the development of an active antibody response to antigen. Infection of seven passively immunized young calves with a virulent strain of bovine herpesvirus type 1 (BHV-1) was performed to determine whether they could become seronegative after the disappearance of maternal antibodies while latently infected with BHV-1. Four uninfected calves were controls. All calves were monitored serologically for 13 to 18 months. In addition, the development of a cell-mediated immune response was assessed by an in vitro antigen-specific gamma interferon (IFN-gamma) production assay. All calves had positive IFN-gamma responses as early as 7 days until at least 10 weeks after infection. However, no antibody rise was observed after infection in the three calves with the highest titers of maternal antibodies. One of the three became seronegative by virus neutralization test at 7 months of age like the control animals. This calf presented negative IFN-gamma results at the same time and was classified seronegative by enzyme-linked immunosorbent assay at around 10 months of age. This calf was latently infected, as proven by virus reexcretion after dexamethasone treatment at the end of the experiment. In conclusion, this study demonstrated that BHV-1-seronegative latent carriers can be obtained experimentally. In addition, the IFN-gamma assay was able to discriminate calves possessing only passively acquired antibodies from those latently infected by BHV-1, but it could not detect seronegative latent carriers. The failure to easily detect such animals presents an epidemiological threat for the control of BHV-1 infection.

Detection of BHV-1 in a naturally infected bovine fetus by a nested PCR assay

Bovine herpesvirus 1 (BHV-1) is frequently associated with abortion in naturally and experimentally infected cattle. Most of the virus isolation and immunofluorescent antibody protocols described in the literature for detecting BHV-1 in bovine foetuses are rather laborious, costly and time-consuming. The detection is described of BHV-1 in the tissues of a naturally aborted bovine foetus by a nested PCR assay with no further hybridization procedures. Optimal results were achieved by filtering the foetal tissues on a chromatography column before DNA extraction, by using two pairs of primers in a nested PCR and by evaluating the amplification products on silver-stained polyacrylamide gels. This nested PCR was faster and easier to perform than the virus isolation test. To our knowledge, this is the first time that BHV-1 has been detected in the tissues of a naturally infected bovine foetus by means of a nested PCR. The test seems to be a practical alternative for rapid detection of BHV-1 in bovine foetus.

A high sensitivity-nested PCR assay for BHV-1 detection in semen of naturally infected bulls

Several different PCR protocols for the detection of Bovine herpesvirus-1 (BHV-1) in bovine semen, are available in the literature. Most of them are rather laborious and the majority were performed on laboratory samples, artificially contaminated semen or semen provided from experimentally inoculated animals. Furthermore, to obtain higher levels of sensitivity, additional dot-blot procedures are frequently necessary. We describe the detection of BHV-1 in bovine semen and the supernatant of cell cultures with titres of 0.001 TCID50/50 microliter by a nested PCR assay, with no further hybridization procedures. The high sensitivity was achieved by filtering the semen samples on chromatography columns before DNA extraction, by using two pairs of primers in a nested PCR and by evaluating the amplification products on silver-stained polyacrylamide gels. Specificity of the amplified fragments was confirmed by RFLP and sequence analysis of the PCR products. This nested PCR procedure was performed in parallel with viral isolation (VI) on 101 semen samples provided from naturally infected bulls housed at an artificial insemination centre. The nested PCR was shown to be more sensitive, faster and easier to perform than the standard VI test. To our knowledge, it is the most sensitive PCR test for BHV-1 detection in bovine semen and could be easily used for routine diagnosis.

Herpesviral abortion in domestic animals

Abortion or neonatal disease may follow infection with several alpha, beta and gamma-herpesviruses. The alpha-herpesvirus, equid herpesvirus-1 (EHV-1), causes single or epizootic abortions or neonatal deaths in equids, and the closely related virus EHV-4 causes sporadic equine abortions. In cattle, the alpha-herpesviruses, bovine herpesvirus-1 (infectious bovine rhinotracheitis virus) and bovine herpesvirus-5 (bovine encephalitis virus), and a gamma-herpesvirus, bovine herpesvirus-4, have all been implicated as causes of abortion. In pigs, suid herpesvirus-1 (SHV-1: pseudorabies virus), an alpha-herpesvirus, and SHV-2 (porcine cytomegalovirus), a beta-herpesvirus, each cause abortion or neonatal piglet losses. Caprine herpesvirus-1, canine herpesvirus and feline herpesvirus-1, all alpha-herpesviruses, cause abortions or neonatal deaths in goats, dogs and cats, respectively. This review discusses the pathogenesis, pathology and laboratory diagnosis of these herpesviral abortions and neonatal diseases, with an emphasis on experimental studies of each disease. Alternative reviews covering other aspects of each infection, such as the genetic and antigenic structure of the viruses, host immune responses and approaches to vaccination and disease control are indicated at appropriate points in the text.

Antibody isotype responses to experimental infection with bovine herpesvirus 1 in calves with colostrally derived antibody

Calves, both positive and negative for maternal antibody to bovine herpesvirus 1 (BHV-1), were infected with BHV-1 and their serum antibody isotype responses were measured post-infection. In the case of maternal antibody negative calves there was a classical humoral response to the virus with an early IgM peak followed by IgG1 and IgG2 responses. In maternal antibody positive calves, although infection was established, no active antibody response was detected in serum except for a transient IgM peak in a single calf. By contrast, a delayed-type hypersensitivity test response could be elicited in both groups of calves by intradermal inoculation of nucleocapsid antigen at 4.5 months after the initial infection. The intradermal antigen also stimulated an antibody response. In calves with high levels of maternal antibody at the start of the experiment, and which were not subsequently infected, maternal antibody waned to negative levels by seven months of age. They were skin test negative and did not show a serological response to skin test antigen. It was concluded that isotype specific serology could not be used to distinguish calves with passive immunity to BHV-1 from those with active immunity and putative latent infection. Although the skin test had potential to provide such a distinction, it could compromise future serological monitoring of the animals.

Bovine herpesvirus 1 in semen of bulls and the risk of transmission: a brief review

Outbreaks of bovine herpesvirus 1 (BHV1) infections in artificial insemination centres can run a clinical or subclinical course. Clinical signs vary from mild to severe balanoposthitis and may be associated with a decrease in semen quality. After intranasal as well as intrapreputial infection, BHV1 can replicate in the preputial and penile mucosae, although the pattern of virus shedding in semen differs considerably per individual bull. Beyond the primary phase of a genital infection, BHV1 remains latent in sacral ganglia, and consequently a protracted course of intermittent virus excretion may follow. The seminal plasma rather than the sperm cells contains the BHV1. Diluting the semen before inoculating cell cultures appears to be the best method to neutralize its toxic activity and to achieve optimal virus isolation results. Detection of BHV1 in semen by polymerase chain reaction seems to be more sensitive than virus isolation. Not each extended semen straw contains virus when the virus titre in the ejaculate is low. The minimal dose to infect a cow by artificial insemination may be more than 32 infectious virus particles. Such an infection may lead to fertility disturbances, mainly endometritis. The risk of transmitting BHV1 to inseminated cows by using BHV1-seropositive bulls for artificial insemination is substantially reduced if two straws per semen batch are assayed for virus and if each positive batch is destroyed.

Excretion of bovine herpesvirus 1 in semen is detected much longer by PCR than by virus isolation

To compare the sensitivities of PCR and virus isolation and to examine the course of virus excretion in semen, we intrapreputially inoculated eight bulls with bovine herpesvirus 1 (BHV1) and used two bulls as sentinels. From these bulls, we collected a large panel of semen samples during 65 days postinfection (dpi). At 44 dpi the bulls received dexamethasone to reactivate putatively latent virus. We analyzed the semen samples by virus isolation on egg yolk-extended semen (VIE test), by virus isolation on fresh semen (VIF test), and by a PCR test on egg yolk-extended semen. Of the 162 semen samples that were collected, the VIE test scored 24 positive, the VIF test scored 51 positive, and the PCR test scored 118 positive. At 6 dpi all samples from the inoculated bulls were found to be positive by all three tests. From 9 to 44 dpi most samples were found to be negative by both virus isolation tests but positive by the PCR test. From 48 to 55 dpi the dexamethasone treatment induced virus reactivation, which was evidenced by an increase in the number of positive VIE, VIF, or PCR tests. From 58 to 65 dpi all samples were found to be negative in both virus isolation tests, but several samples were still found to be positive by the PCR test. To determine whether BHV1 DNA was present in the dorsal root ganglia of the infected bulls, we analyzed by PCR several thoracic, lumbar, and sacral ganglia collected at 65 dpi. BHV1 DNA was frequently present in the third, fourth, and fifth sacral ganglia, and semiquantitative PCR analysis showed that the highest amounts of BHV1 DNA (10 to 30 molecules of BHV1 DNA per 10(5) cells) were present in the third sacral ganglion, The results demonstrate that the PCR test detected five times as many positive semen samples as the VIE test. Hence, intrapreputially infected bulls excrete BHV1 in semen much longer than recognized until now.

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.

Rapid detection of bovine herpesvirus 1 (BHV 1) using the polymerase chain reaction

A polymerase chain reaction (PCR) assay based on primers from the viral gI glycoprotein gene detected 3 fg pure BHV-1 DNA, 0.1-1.0 TCID50 or a single infected cell. No amplification was observed with DNA from BHV-2, BHV-3, BHV-4, OHV-1 or OHV-2. However, a fragment of the correct size was amplified using DNA from herpesviruses isolated from reindeer, red deer and goats. The PCR assay was able to detect virus in nasal swabs up to 14 days after experimental infection of cattle and there was a good correlation when PCR was compared with virus isolation for the detection of BHV-1 in clinical field samples. Detection of BHV-1 in fetal bovine serum and semen samples was also successful.

The dangers of disease transmission by artificial insemination and embryo transfer

This review summarizes the major infectious diseases of the three major agricultural species (cattle, sheep and pigs) and horses, and presents the evidence for and against the possibility of infectious agents being transmitted between animals via the venereal route or by the use of semen or early embryos in commercial artificial insemination (AI) or embryo transfer (ET). Cattle feature most prominently in the widespread distribution of frozen semen, and national and international organizations have set out guidelines to work towards disease-free bull studs with semen free from potential pathogens. With the control of major epizootic diseases, attention has been focused on such diseases as IBR, BVD and blue tongue, where clinical signs are rarely evident but the detection of virus in semen is of great importance. New information on the relevance of bacterial disease such as Mycobacterium paratuberculosis, campylobacteriosis and leptospirosis is reviewed, along with details of the mycoplasma and ureaplasma species of the bull's genital tract. Bovine spongiform encephalopathy (BSE) has attracted much research and semen is not regarded as a source of infection. New work on the pathogenesis of a number of diseases and the use of new biotechnology in diagnosis is included. The International Embryo Transfer Society (IETS) has encouraged a great deal of experimental work--much originating in Canada--on the risk of transmission of disease from donors to recipients via a 7-day-old blastocyst. There has been much success in demonstrating that with an approved protocol of handling the embryos, to date there is very little danger in disease transmission with both viruses and bacteria. The mycoplasma group appear more intractable and the role of BSE is still being evaluated. In sheep, scrapie, Brucella ovis infection and blue tongue feature in current work. In the pig there is a surge in international movement of pig semen, and Aujeszky's disease and the new so-called Blue Ear disease feature prominently. Much work is in progress on infectious agents likely to be found in the semen of stallions, with an expanding trade in the international movement of chilled and frozen semen. Equine embryo transfer experiments are hampered by the very limited number of embryos available. Reference is also made to the further risk of disease transmission by in vitro manipulated embryos.

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.

Risk of infection with bovine herpes virus 1 (BHV1): a review

Bovine Herpes Virus 1 (BHV1) consists of three subtypes, which probably differ in their epizootiological characteristics. BHV1 subtypes 1 and 2a are mainly associated with the respiratory form of the disease (IBR), subtype 2b with IPV/IBP, and subtype 3 with encephalitis. BHV1 subtype 1 is excreted in high titres in nasal secretions and spreads more effectively than the other subtypes. Cattle are the only significant source of viral spread. Although other species may become infected, they probably do not contribute to the spread of BHV1. Airborne transmission or spread of the virus by humans is believed to be of minor importance.

Transmission of IBR/IPV virus in bovine semen: A case report

The transmission of IBR/IPV virus in imported semen is reported. Some of the inseminated animals showed seroconversion and, in accordance with Swiss law, had to be eliminated. To avoid such cases in international sperm exchange, methods of detecting IBR/IPV virus need to be improved. In the longer term, AI centres must be established in which all bovine stock is seronegative for IBR/IPV.