The dangers of disease transmission by artificial insemination and embryo transfer

In-Depth Analysis of an Obligate Anaerobe Paraclostridium bifermentans Isolated from Uterus of Bubalus bubalis

Simple Summary

Non-specific uterine infections in bovine (uterine line inflammation) are a significant issue for the dairy industry. These infections are responsible for significant financial losses all over the world. Paraclostridium bifermentans is an obligate anaerobe, gram-positive rod-shaped bacteria belonging to the Clostridia class and the Peptostreptococcaceae family produces endospores. This bacterium has the ability to infiltrate bovine uterine endometrial epithelial cells and cause infection in the endometrium epithelial cells. Our study found that an examination of a buffalo uterus with yellowish purulent discharge reported the presence of pathogenic bacteria Paraclostridium bifermentans, where its genomic characterization, substrate utilization, and antibiotic susceptibility potentiality was studied. This discovery indicates the presence of virulence genes as well as pathogenic features. This is the first report of P. bifermentans from the bovine uterus environment.

Abstract

Chronic non-specific contamination of the reproductive tract in animals is a major issue during early postpartum, natural coitus, or artificial insemination. Uterine infection is one of the major concerns reducing fertility, production loss, and early culling of the animals. Therefore, the aim of this study was to identify any novel bacterium if present in the uterine environment of Bubalus bubalis causing infections. A strictly anaerobic bacterial strain designated as Paraclostridium bifermentans GBRC was isolated and characterized. Bacterium was found to be Gram positive moderate rod with motility. The optimum growth was observed at 40 ± 2 °C. The pathogenic characteristics of the GBRC strain, such as hemolysis, gelatin hydrolysis, and the production of volatile sulfur compounds, were similar to those seen in the epithelial layer invading pathogenic strains. Assembled genome size was 3.6 MB, with 78 contigs, and a G + C content of 28.10%. Furthermore, the whole genome sequence analysis confirmed the presence of genes encoding virulence factors and provided genomic insights on adaptation of the strain in the uterine environment. Based on the phenotypic and genetic differences with phylogenetic relatives, strain GBRC is proposed to represent a first reported species of the genus Paraclostridium with potential pathogenic character, from the buffalo uterine environment. This study analysis of the GBRC strain serves as a key reference point for the investigation of potential pathogenic strains that may cause endometritis and metritis in bovine.

Development of a droplet digital PCR assay to detect bovine alphaherpesvirus 1 in bovine semen

Background

Infectious bovine rhinotracheitis (IBR) caused by bovine alphaherpesvirus 1 (BoHV-1) is one of the most important contagious diseases in bovine. This is one of the most common infectious disease of cattle. This has led to high economic losses in the cattle farming industry. BoHV-1 can potentially be transmitted via semen during natural or artificial insemination (AI). Therefore, testing methods for the early diagnosis of BoHV-1 infection are urgently needed for international trade of ruminant semen. In this study, we developed a novel droplet digital PCR (ddPCR) assay for the detection of BoHV-1 DNA in semen samples.

Results

The ddPCR results showed that the detection limit was 4.45 copies per reaction with high reproducibility. The established method was highly specific for BoHV-1 and did not show cross-reactivity with specify the organisms (BTV, BVDV, Brucella, M . bovis). The results of clinical sample testing showed that the positivity rate of ddPCR (87.8%) was higher than that of qPCR (84.1%).

Conclusions

The ddPCR assay showed good accuracy for mixed samples and could be a new added diagnostic tool for detecting BoHV-1.

Sperm interaction with the uterine innate immune system: toll-like receptor 2 (TLR2) is a main sensor in cattle

During the passage through the female reproductive tract, sperm interact with various compartments and their immune systems. The immune system that protects the female against pathogens also could destroy sperm or prevent them from reaching the site of fertilisation. In particular, the uterine innate immune response is crucial from the perspectives of both the sperm and the uterus. Following insemination, sperm immediately start to trigger inflammation in the uterus by entering uterine glands and activating an innate immune response. In cattle, the activation occurs mainly via TLR2 signalling, if not the only one, between sperm and the uterine epithelium lining the glands. This acute immune response is manifested as the upregulation of mRNA expression of IL8, TNFA, IL1B , and PGES . As a consequence, many sperm are trapped by polymorphonuclear neutrophils, the first and major component of innate immunity. The sperm-induced uterine innate immune responses apparently serve to clear the uterus of excess sperm and, importantly, prepare the endometrium for implantation. Pathophysiological conditions in the uterus seriously disrupt this phenomenon, and thus could directly decrease fertility.

Concurrent detection of bovine viral diarrhoea virus and bovine herpesvirus-1 in bulls' semen and their effect on semen quality

Reproductive diseases may have destructive effects on the fertility of cattle. Bovine viral diarrhoea virus (BVDV) and bovine herpes virus-1 (BoHV-1) are potent viral pathogens linked to reproduction. Thus, the aim of this study was to utilize raw semen samples for conventional and molecular detection of BVDV and BoHV-1, simultaneously. Additionally, the effect of virus infection on the semen quality of naturally infected bulls has been investigated. Therefore, 40 bulls were employed for semen collection, evaluation and testing for both viruses by virus isolation, direct fluorescent antibody technique (FAT) and SYBR Green real-time PCR assay. In virus isolation results, no cytopathic effect (CPE) was observed for BVDV on cell culture whereas, eight (20%) samples displayed characteristic grape-like clusters of cells for BoHV-1. By direct FAT, 12 (30%) positive BVDV and 8 (20%) positive BoHV-1 samples were confirmed. SYBR Green real-time PCR analysis using 48 h inoculated semen samples revealed 14 (35%) and 8 (20%) positive samples for BVDV and BoHV-1, respectively. Statistical analysis of semen evaluation parameters showed a significant difference between viral-infected and free groups represented by increased sperm abnormalities and decreased sperm motility, liveability and concentration. However, there was no significant difference among BVDV, BoHV-1 and mixed-infected groups. The study concluded that BVDV and/or BoHV- 1 infected bulls expressed low semen quality. Real-time PCR was confirmed to be the ideal laboratory assay for detection of both viruses in semen.

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.

Diagnosing bluetongue virus in domestic ruminants: current perspectives

This review provides an overview of current and potential new diagnostic techniques against bluetongue virus (BTV), an Orbivirus transmitted by arthropods that affects ruminants. Bluetongue is a disease currently notifiable to the World Organization for Animal Health (OIE), causing great economic losses due to decreased trade associated with bluetongue outbreaks and high mortality and morbidity. BTV cross-reacts with many antigenically related viruses including viruses that causes African Horse sickness and epizootic haemorrhagic disease of deer. Therefore, reliable diagnostic approaches to detect BTV among these other antigenically related viruses are used or being developed. The antigenic determinant for differentiation of virus species/serogroups among orbiviruses is the VP7 protein, meanwhile VP2 is serotype specific. Serologically, assays are established in many laboratories, based mainly on competitive ELISA or serum neutralization assay (virus neutralization assay [VNT]) although new techniques are being developed. Virus isolation from blood or semen is, additionally, another means of BTV diagnosis. Nevertheless, most of these techniques for viral isolation are time-consuming and expensive. Currently, reverse-transcription polymerase chain reaction (RT-PCR) panels or real-time RT-PCR are widely used methods although next-generation sequencing remains of interest for future virus diagnosis.

Bovine herpesvirus 1 can impact the bovine oocyte development during in vitro maturation

Bovine herpesvirus 1 (BoHV-1) disseminates easily, is difficult to control, and is widely spread in cattle herds worldwide. BoHV-1 causes a broad range of losses to the cattle industry, mainly concerning reproduction. Previous studies involving experimental infection of BoHV-1 in an in vitro embryo production system have reported impairment of embryonic development by BoHV-1. In this study, we evaluated the interference of BoHV-1 in the in vitro maturation system of cumulus-oocyte complexes (COCs) and denuded oocytes (DOs) cultured with a cumulus cell suspension. Blood samples and ovaries were collected from slaughterhouse cows unvaccinated against BoHV-1. Using virus neutralization assays, the seropositive animals were classified according to their antibody titers. The oocytes were recovered by follicular aspiration and divided into two groups, COCs and DOs, which were evaluated for their nuclear maturation capacity using immunofluorescence assays by laser scanning confocal microscopy. Two experiments were carried out: (I) in vitro maturation of COCs and DOs after artificial infection of seronegative animals and (II) in vitro maturation of COCs and DOs of seropositive animals. In experiment I, a difference (P < 0.01) was observed between the maturation rates of the control group COCs (78.2%) and the infected COCs (43.6%). In experiment II, there was a difference (P < 0.01) in the maturation rate between animals with antibody titers ≥16 (56.9%) and the control group (79.4%). Immunofluorescence assays identified BoHV-1 in the COCs and DOs. Therefore, it was concluded that BoHV-1 affects the in vitro maturation process in both in vitro and natural infections.

Herpesvírus bovino tipo 1 (BoHV-1): método de diagnóstico e sua influência na qualidade espermática em touros infectados experimentalmente

RESUMO O herpesvírus bovino tipo-1 (BoHV-1) é um vírus amplamente distribuído no Brasil e no mundo, havendo um crescente número de estudos envolvendo métodos de diagnóstico e o seu impacto na reprodução animal. O objetivo deste trabalho foi identificar o material genético do BoHV-1 no sêmen de touros infectados experimentalmente por meio da técnica de PCR e avaliar a influência do vírus sobre a qualidade espermática desses animais. A técnica de PCR foi satisfatória, permitindo identificar a presença do material genético do vírus no sêmen de todos os animais a partir de sete dias pós-infecção, com persistência de 21 até 28 dias. Apesar da presença do vírus BoHV-1 por um longo período no sêmen dos animais experimentais, não foram observados efeitos deletérios na qualidade do sêmen fresco e nem após a criopreservação.

Progress and challenges of fish sperm vitrification: A mini review

To survive low temperature is required for a long-term storage (cryopreservation), cells should be vitrified to a state in which intracellular water is solidified without ice crystal formation. Two different approaches are described for fish sperm cryopreservation: 1) sperm conventional cryopreservation, in which extracellular water is partially crystallized and 2) sperm vitrification, in which both intra- and extra-cellular liquids are vitrified. Sperm vitrification has been applied to some fish species with limited success. Traditional vitrification requires rapid cooling/warming rates, small sample carriers, and using high permeable cryoprotectant concentrations. The latter cause cytotoxic effects which must be well managed and will require continuous effort to match an appropriate cryoprotectant with suitable apparatus and warming methods. Novel cryoprotectant-free sperm vitrification approach has been applied to several fishes. This review summarizes development of basic procedures and discusses advantages and disadvantages of vitrification when applied it to fish sperm.

Presence of Mycoplasma agalactiae in semen of naturally infected asymptomatic rams

The purpose of the present study was to assess the presence of Mycoplasma agalactiae (Ma), the main causative agent of ovine contagious agalactia (CA), in semen of naturally infected rams. Therefore, semen samples from 167 rams residing in three different artificial insemination (AI) centers of a CA-endemic area were studied by microbiological and molecular techniques. In addition, serial ejaculates from the same rams were evaluated to determine the excretion dynamics of Ma. Of the 384 samples studied, Ma was detected in 56 (14.58%) which belonged to 44 different rams (26.35%). These findings confirm the ability of Ma to be excreted in semen of asymptomatic rams. Furthermore, these results also evidence the presence of these asymptomatic carriers of Ma in ovine AI centers, representing a serious health risk regarding the spread and maintenance of CA, especially in endemic areas. Moreover, the excretion of Ma in semen also points to the risk of venereal transmission of this disease. The current results highlight the need to implement control measures to prevent the admission of infected rams in AI centers and the necessity to continuously monitor semen samples to effectively detect infected individuals.

Caprine arthritis encephalitis: an example of risk assessment for embryo trading

The risk of transmission of caprine arthritis encephalitis virus (CAEV) during embryo transfer has been demonstrated in vivo through the detection of CAEV proviral DNA in: (1) flushing media for embryo collection; (2) cells of the cumulus oophorus surrounding the oocytes, ovarian follicle, oviduct and uterine tissues; and (3) testis, epididymis, vas deferens and vesicular glands. Experimentally infected embryos without a zona pellucida (ZP), washed 10 times with Minimum Essential Media (MEM) and 5% Fetal Calf Serum (FCS) solution, were capable of transmitting CAEV. In vitro we demonstrated that granulosa, oviductal, epididymal and embryo cells are fully susceptible to CAEV infection and allow active replication. However, AI with in vitro-infected semen can result in the production, after ten washing, of CAEV-free embryos, and ten washing in vitro- or in vivo-infected embryos with an intact ZP, or ten washing oocytes with an intact ZP, resulted in the production of virus-free female gametes or embryos that can be used for IVF or embryo transfer. Therefore, we have demonstrated that: (1) that CAEV-free embryos can be produced by IVF using spermatozoa infected in vitro by CAEV; and (2) embryo transfer can be used under field conditions to produce CAEV-free kids from CAEV-infected biological mothers.

Distribution of Mycobacterium avium subsp. paratuberculosis in a Subclinical Naturally Infected German Fleckvieh Bull

Although it has been known for years that Mycobacterium avium subsp. paratuberculosis (MAP) is detectable in the reproductive organs and semen of infected bulls, only few studies have been conducted on this topic worldwide. This study surveyed the MAP status of a bull, naturally infected due to close contact with its subclinically infected parents over a period of 4 years. From the age of 7 weeks to necropsy, faecal, blood and, after sexual maturity, semen samples were drawn repeatedly. Already at the first sampling day, MAP-DNA was detected in faeces by semi-nested PCR. True infection was confirmed by the detection of MAP-DNA in blood at the age of 40 weeks. In total, MAP-DNA was present in 25% faecal (34/139), 16% blood (23/140) and 5% semen (4/89) samples, including MAP-free intervals of up to 9 weeks. MAP genome equivalents (MAP-GE) of up to 6.3 × 10⁶ /g faeces and 1.8 × 10⁵ /ml blood were determined. Cultivation of MAP occurred only in three of 137 faecal and two of 109 blood, but never in semen samples. Over the whole period, the bull was a serological negative MAP shedder. During necropsy, 42 tissue samples were collected. Neither macroscopic nor histological lesions characteristic of a MAP infection were observed. Cultivation of MAP in tissue sections failed. However, MAP-DNA was spread widely in the host, including in tissues of the lymphatic system (7/15), digestive tract (5/14) and the urogenital tract (5/9) with concentrations of up to 3.9 × 10⁶ MAP-GE/g tissue. The study highlighted the detection of MAP in male reproductive organs and semen. It supports the hypothesis that bulls may probably transmit MAP, at least under natural mating conditions. In artificial insemination, this might not be relevant, due to antibiotics included currently in semen extenders. However, the survivability of MAP in this microenvironment should be investigated in detail.

A review of sexually transmitted bovine trichomoniasis and campylobacteriosis affecting cattle reproductive health

The objective is to discuss sexually transmitted diseases caused by Tritrichomonas foetus (T foetus) and Campylobacter fetus (C fetus) subsp. venerealis, with a focus on prevalence, pathogenesis, and diagnosis in cows and bulls. Diagnosis and control are problematic because these diseases cause severe reproductive losses in cows, but in bulls are clinically asymptomatic, which allows the disease to flourish, especially in the absence of legislated control programs. We review research regarding prophylactic systemic immunization of bulls and cows with antigens of T foetus and C fetus venerealis and their efficacy in preventing or clearing preexisting infections in the genital tract. Current diagnostic methods of C fetus venerealis and T foetus (microbial culture and PCR) should be improved. Review of the latest advances in bovine trichomoniasis and campylobacteriosis should promote knowledge and provide an impetus to pursue further efforts to control bovine sexually transmitted diseases.

Infectious pathogens potentially transmitted by semen of the black variety of the Manchega sheep breed: Health constraints for conservation purposes

Conservation of genetic resources from endangered breeds may be conducted through germinal banks. Preservation of healthy samples is paramount to avoid preserving pathogens shed with germinal products. The black variety of Manchega sheep (BMS), and endangered breed endemic to south-central Spain, is the subject of a conservation program; a germinal bank has been recently established. However, several pathogens circulating in BMS flocks may be shed with semen and threaten BMS preservation. Therefore, we investigated the sanitary status of BMS flocks and semen samples from 4 of the 17 flocks in which this variety is bred worldwide. A serological screening for Maedi-Visna virus, bluetongue virus, Pestivirus spp., Brucella spp., Coxiella burnetii, Chlamydophila spp., Mycobacterium tuberculosis complex, Mycobacterium avium paratuberculosis, Anaplasma spp., Mycoplasma agalactiae, Toxoplasma gondii and Neospora caninum was performed to assess for pathogens potentially shed by semen. Semen samples from 11 of the 35 BMS rams and 4 samples from coexisting rams of the white variety (WMS) were analyzed by PCR to detect Maedi-Visna virus, C. burnetii, Anaplasma marginale, Anaplasma phagocytophilum and T. gondii. Maedi-Visna virus RNA was detected in 3 semen samples (2 BMS and 1 WMS) while C. burnetii DNA was detected in 3 samples from WMS rams. Pathogens that can be transmitted by semen were present in BMS flocks, and Maedi-Visna virus and C. burnetii showed the highest potential for transmission by artificial insemination. Our results point to the need of testing semen samples kept for conservation purposes of BMS before using them for artificial insemination.

A longitudinal study to characterize the distribution patterns of Mycobacterium avium ssp. paratuberculosis in semen, blood and faeces of a naturally infected bull by IS 900 semi-nested and quantitative real-time PCR

Johne's disease is caused by Mycobacterium avium ssp. paratuberculosis (MAP) and has been recognized as an important bacterial infection in ruminants. Although MAP has been detected in semen and within the reproductive organs of bulls, the bacterial distribution and shedding patterns are currently not well characterized. Our investigation was performed to detect and quantify MAP in faeces, semen and blood samples repeatedly drawn from a naturally infected but asymptomatic 18-month-old German Simmental breeding bull candidate over a period of 3 years (June 2007-November 2010). Qualitative and quantitative polymerase chain reaction (PCR) techniques were used to correlate the presence and matrix-specific amounts of MAP. In total, 65 sampling dates were selected. Mycobacterium avium ssp. paratuberculosis was detected intermittently in all matrices with MAP-free intervals of up to 18 weeks by an IS900 semi-nested PCR. The number of MAP-positive results from semen and blood samples was higher than from faecal samples. A quantitative polymerase chain reaction detected the highest MAP contents in faeces (10(3) -10(6) MAP/g), while lower amounts were found in semen and blood samples (10(2) -10(5) MAP/ml). Although no significant agreement was calculated between the presence of MAP in faeces and blood, a statistically significant positive correlation between its occurrence in semen and blood was determined (r = 0.38, P < 0.05, n = 29). The present study contributes to a more detailed understanding of MAP distribution patterns in faeces, semen and blood of a subclinically infected breeding bull candidate. It highlights the possible role of breeding bulls as a source of MAP transmission and indicates the need for further monitoring and hygienic measures to prevent the spread of the infection via semen.

Detection of paratuberculosis in breeding bulls at pakistani semen production units: a continuous source of threat

Paratuberculosis is a chronic bowel disease of ruminants caused by Mycobacterium avium subsp. paratuberculosis (MAP). Its secretion through semen highlights the importance of paratuberculosis-free breeding bulls. The breeding and teaser bulls at three semen production units (SPUs) located in Punjab, Pakistan, were screened for the presence of antibodies against MAP. A total of 253 samples were collected from SPUs and a commercially available indirect screen ELISA (Is-ELISA) was applied. Is-ELISA detected antibodies in 20 (24.6%), 16 (22.8%), and 17 (16.6%) samples from SPU-I, SPU-II, and SPU-III, respectively. Collectively, seroprevalence of 20.0% (47/235) in breeding bulls and 33.3% (6/18) in teaser bulls was observed, and thus it poses a potential threat of disease spread to a high number of heifers and cows through artificial insemination. Therefore, this paper highlights the presence of the disease for the first time at SPUs and triggers attempts to ascertain the prevalence of paratuberculosis throughout the country.

Consecutive excretion of Mycobacterium avium subspecies paratuberculosis in semen of a breeding bull compared to the distribution in feces, tissue and blood by IS900 and F57 quantitative real-time PCR and culture examinations

Paratuberculosis (Johne's disease) has emerged as one of the most important diseases in cattle. The role of infected bull semen in the spread of infection remains unclear, as the correlation between the amount of excreted Mycobacterium avium subsp. paratuberculosis (semen and feces) and the infection load (blood and tissues) has not been defined. The aim of the present study was to study by culture, and a quantitative real-time polymerase chain reaction, the presence of bacteria in consecutive semen, blood, and fecal samples collected from one infected Piedmont breeding bull during a 380-day period. Five out of seven blood samples and all nine semen samples were positive in the real-time quantitative polymerase chain reaction with 10¹ to 10² and 10² to 10⁴ copies of IS900/F57 per ml, respectively. In all, there were 9 fecal culture positive samples with too numerous to count colony forming units and positive real-time quantitative polymerase chain reactions ranging from 10⁵ to 10⁷ copies of IS900/F57. After the bull was euthanized, Mycobacterium avium subsp. paratuberculosis was cultured from various parts of the small and large intestines, liver tissue and lymph nodes and from the epididymis and vesicular glands. The results demonstrate a wide extraintestinal distribution of the bacterium and that breeding bulls should be considered a source of paratuberculosis infection due to their contact with other breeding bulls and a high number of heifers and cows through the natural mating process.

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.

Importation of in vitro-produced Bubalus bubalis embryos from Italy into the United States: a case report

On December 19, 2005, 14 in vitro-fertilized water buffalo (Bubalus bubalis) embryos, which had been cryopreserved by vitrification, were thawed and transferred into B. bubalis recipients in California. The embryos had been produced in Italy, following transvaginal oocyte pickup (TVOPU), with subsequent in vitro maturation, insemination, and culture. This case study relates our experience in meeting the regulatory criteria, established by the Animal Import/Export Office of the USDA-Animal and Plant Health Inspection Service (USDA-APHIS), in order to successfully import these embryos into the USA.

An international inter-laboratory ring trial to evaluate a real-time PCR assay for the detection of bovine herpesvirus 1 in extended bovine semen

Six laboratories participated in a ring trial to evaluate the reliability of a real-time PCR assay for the detection of bovine herpesvirus 1 (BoHV-1) from extended bovine semen. Sets of coded samples were prepared and distributed to each of the laboratories. The sample panel contained semen from naturally and artificially infected bulls, serial dilutions of positive semen with negative semen, semen from uninfected seronegative bulls, negative semen spiked with virus, as well as serial dilutions of reference virus. The samples were tested using a previously validated real-time PCR assay for the detection of BoHV-1 in each participating laboratory. The PCR tests were conducted with four different real-time PCR amplification platforms, including RotorGene 3000, Stratagene MX 3000/4000, ABI 7900, and Roche LightCycler 2.0. Virus isolation using one set of samples was performed in one laboratory. The results of the laboratories were compared with one another, and with those of virus isolation. It was found that the sensitivity and specificity of the real-time PCR test was greater than those of virus isolation (82.7% versus 53.6% and 93.6% versus 84.6%, respectively). A high level of agreement on PCR testing results between the laboratories was achieved (kappa value 0.59-0.95). The results of this study indicate that the real-time PCR assay is suitable for the detection of BoHV-1 in extended semen, and would be a good substitute for the slow and laborious virus isolation, for the screening testing at artificial insemination centres and for international trade.

Molecular detection of BHV-1 in artificially inoculated semen and in the semen of a latently infected bull treated with dexamethasone

Two polymerase chain reaction (PCR) assays specific for glycoprotein B (gB) and glycoprotein E (gE) gene detection, respectively, were adopted for the detection of bovine herpesvirus-1 (BHV-1) in naturally infected bulls. The methods were tested on bovine semen artificially inoculated with BHV-1 and were compared with an optimised virus isolation method. Raw and extended semen samples were diluted in minimal essential medium (MEM) and spiked with equal dose of BHV-1. The extended semen was found to be more toxic for the cells than the raw semen, while the viral DNA could be detected by the PCR method in all tested dilutions of raw and extended semen samples. The sensitivity of both methods was compared also for BHV-1 detection in semen, nasal swabs and leucocytes of a seropositive bull in a different time period after virus reactivation with dexamethasone treatment. The sensitivity of virus detection by the PCR method was equivalent to that of virus isolation in cell culture. However, PCR was shown to be faster and easier to perform and may be a good alternative to virus isolation especially when bovine semen has to be screened for BHV-1 prior to artificial insemination.

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.

Evaluation of virus decontamination techniques for porcine embryos produced in vitro

The objective of this study was to explore approaches to decontaminate embryos either contaminated naturally or under experimental conditions with different viruses. Embryos were obtained from in vitro maturation and fertilisation of porcine oocytes. After 7 days of development, morula and blastocyst stages were exposed for 1 h to the following viruses: encephalomyocarditis virus (EMCV), porcine circovirus type 2 (PCV2), porcine parvovirus (PPV), porcine reproductive and respiratory syndrome virus (PRRSV), and bovine viral diarrhea virus (BVDV) at an infectivity of 100 TCID50/mL. Embryos samples were treated with different washing procedures, which all included the following standard washing solutions: PBS+0.4% BSA (five times for 10 s), Hank's+0.25% trypsin (two times for 60-90 or 120-150 s, or one time of 5 min), Hank's+0.1 mg/mL DNase 1+20 U/mL RNase One (one time of 30 min) and PBS+0.4% BSA again (five times for 10s). Two new approaches were used to improve trypsin treatment, 0.1% hyaluronidase (one time for 5 min) instead of trypsin and a pre-incubation with oviductal cells. Therefore, in the first experiment, oocytes received standard maturation treatments and in the second, they were also co-incubated with oviductal cells for the last 3 h of maturation. The effectiveness of the different washing techniques in removing viruses was evaluated by polymerase chain reaction (PCR) analysis. In the first experiment, trypsin treatment did not eliminate PRRSV, PPV, PCV, and EMCV from contaminated embryos. Surprisingly, treatment with hyaluronidase eliminated all tested viruses. In the second experiment, all viruses tested were removed from the oocytes following the different enzymatic treatments. In conclusion, in vitro embryo decontamination was more effective following exposure to oviductal secretions and hyaluronidase eliminated more virions than trypsin in washing techniques.

Occasional detection of Neospora caninum DNA in frozen extended semen from naturally infected bulls

Recently, the presence of Neospora caninum DNA in semen from naturally infected bulls was reported. In the present work, the presence and quantification of N. caninum by PCR techniques in frozen extended semen straws from naturally infected bulls was investigated. A total of 20 seropositive and five seronegative bulls raised for reproductive purposes in an AI centre were used. Ten extended semen straws from each bull obtained at different time-points during the previous 2 years were selected for Neospora testing. Eight of the seropositive bulls (40%) studied showed at least one positive straw to N. caninum DNA and 14 of their 180 semen straws examined (7.8%) were found to be positive. In all positive samples, N. caninum DNA was consistently detected in the cell fraction and not in the seminal plasma. However, the parasite number in each positive straw was under the detection level of real-time PCR. In parallel, 10 semen straws from each of the five seronegative bulls were also analyzed by the nested-PCR and no N. caninum DNA products were obtained. In order to check the consistent presence of N. caninum in a positive semen batch, three additional semen straws from the same batch of each positive straw from three seropositive bulls were analyzed but N. caninum DNA was only detected in one straw from one bull. In conclusion, we report the sporadic detection of N. caninum DNA in semen straws of naturally infected bulls but the low frequency of contaminated semen straws and the low parasite load observed indicate a minor chance of bovine neosporosis transmission by AI.

Viruses in boar semen: detection and clinical as well as epidemiological consequences regarding disease transmission by artificial insemination

Many viruses have been reported to be present in boar semen, particularly during the viremic phase of the diseases. Some of them, such foot-and-mouth disease virus, porcine reproductive and respiratory syndrome virus, swine vesicular disease virus, porcine parvovirus, picornaviruses, adenoviruses, enteroviruses, Japanese encephalitis virus, pseudorabies virus, African swine fever virus and reoviruses are of particular importance and accurate monitoring prior to and during the presence of boars in AI stations is essential. Various methods may be used to detect these viruses in the animals, or even directly in batches of semen. Cell culture, ELISA and PCR are the most accurate and widely used. Because of the high risk of dissemination of disease via AI, the absolute goal is to provide pathogen-free semen and this is feasible with the adequate measures that are discussed briefly in this paper.

Biosecurity strategies for conserving valuable livestock genetic resources

The foot and mouth disease (FMD) epidemic in the UK in 2001 highlighted the threat of infectious diseases to rare and valuable livestock and stimulated a renewed interest in biosecurity and conservation. However, not all diseases resemble FMD: their transmission routes and pathological effects vary greatly, so biosecurity strategies must take this into account. Realism is also needed as to which diseases to exclude and which will have to be tolerated. The aim should be to minimise disease generally and to exclude those diseases that threaten the existence of livestock or preclude their national or international movement. Achieving this requires a team effort, bearing in mind the livestock species involved, the farming system (‘open’ or ‘closed’) and the premises. Effective biosecurity demands that practically every aspect of farm life is controlled, including movements of people, vehicles, equipment, food, manure, animal carcasses and wildlife. Above all, biosecurity strategies must cover the disease risks associated with moving the livestock themselves and this will require quarantine if adult or juvenile animals are imported into the herd or flock. The present paper emphasises the important role that reproductive technologies, such as artificial insemination and embryo transfer, can have in biosecurity strategies because they offer much safer ways for getting new genetic materials into herds/flocks than bringing in live animals. Embryo transfer is especially safe when the sanitary protocols promoted by the International Embryo Transfer Society and advocated by the Office International des Epizooties (the ‘World Organisation for Animal Health’) are used. Embryo transfer can also allow the full genetic complement to be salvaged from infected animals. Cryobanking of genetic materials, especially embryos, is another valuable biosecurity strategy because it enables their storage for conservation in the face of contingencies, such as epidemic disease and other catastrophes.

Detection of Neospora caninum in semen of bulls

In cattle, transplacental infection is the main route of Neospora caninum transmission, but postnatal transmission by the oral uptake of sporozoite-containing oocysts shed by dogs may also be possible. Other routes of horizontal transmission, such as the venereal route, have not been investigated. In this study, we evaluated the presence of N. caninum DNA by a nested-PCR in fresh non-extended semen and frozen extended semen straws of five Holstein-Friesian bulls with naturally-acquired neosporosis. The infection status was assessed by an immunofluorescent antibody test (IFAT) and confirmed by immunoblotting (IB). Because of inhibitory components of semen, a protocol was developed to purify N. caninum DNA from bovine semen. Sporadically, N. caninum DNA was detected in non-extended fresh semen samples and frozen extended semen straws of the five seropositive bulls. In all positive samples, specific DNA was consistently found in the cell fraction of semen and not in seminal plasma. The parasite mean load in positive fresh semen samples determined by a real-time PCR was low oscillating between 1 and 2.8 parasites/ml of semen (maximum parasite load detected in one sample was 7.5 parasites/ml of semen). In parallel, another three similar but uninfected bulls acted as controls and no N. caninum DNA was amplified in any of their fresh and straw semen samples assayed. Whether venereal transmission plays a role in the spread of bovine neosporosis needs to be determined.

Comparison of polymerase chain reaction and cell culture for the detection of Chlamydophila species in the semen of bulls, buffalo-bulls, and rams

Two hundred and thirty six semen samples were collected from 120 bulls, 60 buffalo-bulls, and 56 rams located on farms of known history of infection with Chlamydophila species. All semen samples were examined by polymerase chain reaction (PCR) and cell culture techniques for detection of Chlamydophila species. The primers were selected to allow the amplification of all target species in a single reaction by identifying conserved sequences in the omp2 gene. PCR assay detected more positive samples (36) from the semen samples collected from different animal species than were detected by the culture method (21). The results indicated that all culture-positive semen samples (21) from different species were PCR positive. The detection limit of the PCR assay was determined with DNA extracted from fourfold serial dilution of C. abortus (B577) and C. pecorum (11/88) cultures and found to be 0.25 inclusion-forming units (IFU) per PCR, while the culture method could not detect less than 4 IFU. This is the first report using PCR for the detection of Chlamydophila species in buffalo-bulls' semen and the assay provides a simple, sensitive, rapid, and reliable means for the detection and identification of the organism.

Detection of classical swine fever virus in boar semen by reverse transcription-polymerase chain reaction

A seminested reverse transcription-polymerase chain reaction (RT-PCR) was developed for the detection of classical swine fever virus (CSFV) in semen. Five boars were inoculated intranasally with CSFV isolate propagated in PK15 cells. Two boars inoculated with the supernatant of noninfected PK15 cells were kept as controls. Semen and serum samples were collected twice weekly for 63 days postinoculation (dpi). Samples were tested for the presence of antibodies to CSFV by an enzyme-linked immunosorbent assay and for the presence of CSFV nucleic acid by seminested RT-PCR. Antibodies to CSFV could be detected as early as 7 dpi in 1 boar, and all 5 infected boars were found positive by 14 dpi. CSFV from boar semen was infrequently identified by virus isolation compared with seminested RT-PCR. CSFV nucleic acid was detected in semen by seminested RT-PCR as early as 7 dpi in 3 infected boars and persistently thereafter in all 5 infected boars until 63 dpi. When separated fractions of CSFV-contaminated semen were analyzed by the seminested RT-PCR, the CSFV nucleic acid was detected mainly in seminal fluid and occasionally in nonsperm cells. CSFV antigen was also detected in nonsperm cells from semen smear by immunohistochemistry. Thus, infection via semen, specially through CSFV-infected seminal fluid, seems to be a major route of transmission of CSFV.

Early embryonic cells from in vivo-produced goat embryos transmit the caprine arthritis–encephalitis virus (CAEV)

The aim of this study was to investigate whether cells of early goat embryos isolated from in vivo-fertilized goats interact with the caprine arthritis-encephalitis virus (CAEV) in vitro and whether the embryonic zona pellucida (ZP) protects early embryo cells from CAEV infection. ZP-free and ZP-intact 8-16 cell embryos were inoculated for 2 h with CAEVat the 10(4) tissue culture infectious dose 50 (TCID50)/ml. Infected embryos were incubated for 72 h over feeder monolayer containing caprine oviduct epithelial cells (COECs) and CAEV indicator goat synovial membrane (GSM) cells. Noninoculated ZP-free and ZP-intact embryos were submitted to similar treatments and used as controls. Six days postinoculation, infectious virus assay of the wash fluids of inoculated early goat embryos showed typical CAEV-induced cytopathic effects (CPE) on indicator GSM monolayers, with fluids of the first two washes only. The mixed cell monolayer (COEC + GSM) used as feeder cells for CAEV inoculated ZP-free embryos showed CPE. In contrast, none of the feeder monolayers, used for culture of CAEV inoculated ZP-intact embryos or the noninoculated controls, developed any CPE. CAEV exposure apparently did not interfere with development of ZP-free embryos in vitro during the 72 h study period when compared with untreated controls (34.6 and 36% blastocysts, respectively, P > 0.05). From these results one can conclude that the transmission of infectious molecularly cloned CAEV-pBSCA (plasmid binding site CAEV) by embryonic cells from in vivo-produced embryos at the 8-16 cell stages is possible with ZP-free embryos. The absence of interactions between ZP-intact embryos and CAEV in vitro suggests that the ZP is an efficient protective embryo barrier.

Prion protein is secreted in soluble forms in the epididymal fluid and proteolytically processed and transported in seminal plasma

The presence of prion protein in sperm and fluids collected from different parts of the ram genital tract was investigated by immunoblotting with monoclonal antibodies. A slightly immunoreactive 25- to 30-kDa protein was recognized on Western blots of testicular and epididymal sperm extracts. Immunoreactivity increased on ejaculated sperm extracts and 2 other bands at 35 and 43 kDa also reacted. Seminal plasma showed several immunoreactive bands, the main bands being detected at 43 and 35 kDa, whereas less reactive bands were observed at 30, 25, 20, and <14 kDa. All these bands strongly decreased in the seminal plasma after vasectomy, indicating a testicular or an epididymal origin. Testicular fluid showed almost no reactivity, whereas caudal epididymal fluid contained the 2 strong immunoreactive bands at 43 and 35 kDa and in some cases a faint 30-kDa band. The 43-kDa band was also found in the fluid from the proximal caput, whereas the 35-kDa band appeared in the distal caput. Immunoprecipitation of (35)S-labeled proteins secreted in the epididymal fluid indicated that the 43-kDa form was synthesized in caput and caudal regions and the 35-kDa form in the distal caput to the distal corpus. Treatment of caudal fluid and seminal plasma by N-glycosidase resulted in the formation of 3 bands: 1 highly reactive at about 25 kDa, a second less reactive at about 28 kDa, and a third at approximately 20 kDa. The pattern of prion protein distribution in epididymal fluids was found to be similar in scrapie-infected rams to that of healthy rams. Cauda epididymal fluid and seminal plasma from infected animals could not be treated directly with proteinase K, because of the presence of protease inhibitors. However, the prion protein immunoprecipitated from these fluids was completely cleaved by proteinase K, whereas in the same conditions this from an infected sheep brain gave the usual resistant band pattern.

Epithelial cells from goat oviduct are highly permissive for productive infection with caprine arthritis-encephalitis virus (CAEV)

Caprine oviduct epithelial cells (COEC) are commonly used in in vitro goat embryo production protocols to stimulate early embryonic development. These feeder cells are usually collected from slaughterhouses from unknown serological status animals for caprine arthritis-encephalitis virus (CAEV) infection which is frequent in many regions of the world. Tissues derived from this source may be contaminated with CAEV and the use of such material in in vitro fertilisation systems may contribute to transmission of this pathogen to the cultured embryos and dissemination via embryo transfer (ET). The aim of this study was to determine the permissiveness of COEC to CAEV replication in vitro. Cells were isolated from goats from certified CAEV-free herds and then were inoculated with two CAEV strains: the molecularly-cloned isolate of CAEV (CAEV-pBSCA) and the French field isolate (CAEV-3112). Cytopathic effects (CPE) were observed on cell culture monolayers inoculated with both CAEV strains. Expression of CAEV proteins was shown both by immunocytochemistry using anti-p24 gag specific antibodies and by immunoprecipitation using a hyperimmune serum. The CAEV proteins were correctly and properly processed by artificially-infected COEC and the titers of virus released into the supernatant reached 10(6) TCID(50)/ml 6 days post-inoculation. Although the macrophage lineage cells are the main centre of infection in the virus-positive animal, these findings suggest that epithelial cells may be important in the viral life cycle probably as a reservoir allowing the viral persistence, dissemination and pathogenesis. These results suggest also that the use in in vitro fertilisation systems of co-culture feeder cells that support efficient replication of CAEV to high titers could represent a serious risk for permanent transmission of virus to the cultured embryos and to the surrogate dam involved.

Studies of embryo transfer from cattle clinically affected by bovine spongiform encephalopathy (BSE)

Semen from 13 bulls, eight with clinical bovine spongiform encephalopathy (BSE), was used to artificially inseminate (AI) 167 cows with clinical BSE, and their resultant embryos were collected non-surgically seven days after AI. The viable and non-viable embryos with intact zonae pellucidae were washed 10 times (as recommended by the International Embryo Transfer Society) then frozen. Later, 587 of the viable embryos were transferred singly into 347 recipient heifers imported from New Zealand, and 266 live offspring were born of which 54.1 per cent had a BSE-positive sire and a BSE-positive dam. The recipients were monitored for clinical signs of BSE for seven years after the transfer, and the offspring were monitored for seven years after birth. Twenty-seven of the recipients and 20 offspring died while being monitored but none showed signs of BSE. Their brains, and the brains of the recipients and offspring killed after seven years, were examined for BSE by histopathology, PrP immunohistochemistry, and by electron microscopy for scrapie-associated fibrils. They were all negative. In addition, 1020 non-viable embryos were sonicated and injected intracerebrally into susceptible mice (20 embryos per mouse) which were monitored for up to 700 days, after which their brains were examined for spongiform lesions. They were all negative. It is concluded that embryos are unlikely to carry BSE infectivity even if they have been collected at the end-stage of the disease, when the risk of maternal transmission is believed to be highest.

Effect of transport enrichment medium, transport time, and growth medium on the detection of Campylobacter fetus subsp. venerealis

The combination of medium and growth conditions, including transport enrichment medium (TEM), transport time, TEM incubation time, and growth medium, that best support Campylobacter fetus subsp. venerealis while inhibiting contaminants was studied. The 3 TEMs evaluated, Weybridge, Cary-Blair, and 0.85% saline solution, were inoculated with preputial smegma spiked with C. fetus subsp. venerealis and held in the laboratory for 4 or 24 hours before inoculation onto growth medium. The effect of overnight incubation at 37 C of the TEM was also evaluated. Median scores of C. fetus subsp. venerealis growth and microbial contaminant inhibition were compared within TEM, transport time, overnight incubation, and growth medium groups using the Mann-Whitney U-test and the Kruskal-Wallis test. The proportion of samples with any growth or contamination within each group was also compared using the chi-square test. Results suggest that the growth of C. fetus subsp. venerealis was influenced by 3 of the 4 criteria evaluated. Weybridge TEM more effectively maintained the organism than did either Cary-Blair or 0.85% saline solution (P < 0.001). Transport time of 4 hours rather than 24 hours (P < 0.001) and avoiding overnight incubation of TEM at 37 C (P < 0.001) were associated with improved growth. Significant differences were not identified among growth media; however, Skirrow Campylobacter agar appeared to yield slightly better growth than did either blood agar or Greenbriar Plus agar. Contaminant growth was also influenced by 3 of the 4 variables. Weybridge TEM inhibited contaminant growth more effectively than did either Cary-Blair or 0.85% saline solution (P < 0.001). Transport time was not associated with contaminant growth. Eliminating overnight incubation of TEM reduced contamination (P < 0.01). Skirrow agar was preferred to both blood agar and Greenbriar Plus agar for suppression of contaminants on solid medium (P < 0.001). These results suggest that the detection of C. fetus subsp. venerealis is enhanced when preputial smegma samples arrive at the diagnostic laboratory within 4 hours after inoculation into Weybridge TEM and are transferred to Skirrow agar the same day they arrive in the laboratory.

Detection of Brucella melitensis in semen using the polymerase chain reaction assay

An evaluation of the polymerase chain reaction (PCR) for detection of Brucella melitensis DNA in bovine and ovine semen was performed. Since semen contains different components that inhibit PCR amplification, a protocol was used to purify Brucella-DNA from bovine and ovine semen samples prior to conducting amplification of the targeted DNA. When separated fractions of naturally Brucella contaminated semen were analyzed by the PCR, most of B. melitensis DNA were present in the seminal fluid and non-sperm fractions. The PCR examination results for detection of B. melitensis DNA in different semen fractions were compared with the results for traditional cultural methods of Brucella from semen. The PCR was more sensitive than the traditional cultural methods since it detected Brucella-DNA in 12 (10%) out of 120 semen samples while direct culture detected only 7 (5.8%) in the same semen samples. The limit of detection by PCR was 100 CFU/ml of semen. In addition, the results of PCR were available in one day, whereas isolation and identification of Brucella organisms required days or even weeks. The PCR may be used as a supplementary test for detection of B. melitensis in semen.

Semen from boars infected with porcine reproductive and respiratory syndrome virus (PRRSV) contains antibodies against structural as well as nonstructural viral proteins

The seminal excretion of antibodies against porcine reproductive and respiratory syndrome virus (PRRSV) was examined in a group of five boars experimentally infected by the nasopharyngeal route. By using phage-displayed peptide epitopes from the PRRSV replicase and envelope glycoproteins as ELISA antigen, we were able to separately and specifically assay antibody responses against structural and nonstructural viral proteins. Antibodies against structural as well as nonstructural viral proteins were consistently found in the semen of all boars, beginning from 1-4 weeks postinfection. This is the first report documenting the presence of anti-PRRSV antibodies in boar semen. Seminal antiviral IgA was also detected, and we observed a correlation between seminal IgA responses against nonstructural viral proteins, and the duration of PRRSV RNA excretion in semen. The implications of these findings for the diagnostics and pathogenesis of venereal PRRSV infection are discussed.

Hygienic aspects of storage and use of semen for artificial insemination

The artificial insemination (AI) industry has developed over the last 50 years to the extent that it is used in almost every country in the world. One of the main factors contributing to its success is the confidence of the farmers that germplasm is not associated with pathogens, so that AI can be performed without risks. This has been achieved as a result of a considerable amount of research based on sound scientific data that has identified the major risk pathogens. A summary of these studies, given in this section, shows that despite the large number of agents that could be transmitted via the semen, there are cost-effective means to prevent such hazards. One of the basic rules is that the males should be housed in strictly protected semen collection centres (SCCs). Such centres should be approved by the veterinary authorities based upon specific criteria, which include special housing and operating specifications. This also includes specific means of monitoring the health of individual males through regular clinical examinations, assessment of semen and testings for various diseases. Two new challenges can now be identified, one relevant to so-called emerging diseases the impact of which on the status of the semen donors should always be assessed, and the second, relates to endangered genetic resources which may become extinct without active conservation programmes. The experience gained by the AI industry over the last 50 years should help to solve those problems. Currently, the use of semen derived from approved SCCs warrants their disease-free status.

Failure to detect bovine immunodeficiency virus contamination of stud bull spermatozoa, blood leukocytes, or semen leukocytes in samples supplied by artificial insemination centers

OBJECTIVE

To determine whether bovine immunodeficiency virus (BIV) infection could be detected in spermatozoa, blood leukocytes, or semen leukocytes from stud bulls in artificial insemination centers.

ANIMALS

30 bulls at 3 artificial insemination centers.

PROCEDURE

Polymerase chain reaction testing that used 3 sets of primer pairs targeting pol and env regions of the BIV proviral genome was performed on DNA extracted from semen leukocytes, spermatozoa, and blood leukocytes from each bull. Southern blot analysis was performed to increase sensitivity of detection. Western blot analysis of plasma samples was used to detect antibodies against BIV.

RESULTS

BIV provirus was not detected in DNA samples obtained from semen leukocytes, spermatozoa, or blood leukocytes, and antibodies against BIV were not detected.

CONCLUSIONS AND CLINICAL RELEVANCE

Contrary to our report of high point prevalence of BIV contamination of semen from a single artificial insemination center, bulls of the study reported here did not appear to be infected. Maximum risk of BIV infection in similar bulls was estimated at 10% with a confidence level of 95%.

Comparison of three polymerase chain reaction methods for routine detection of bovine herpesvirus 1 DNA in fresh bull semen

Five bulls were inoculated intrapreputially with Bovineherpes virus 1 (BHV 1), in order to compare the relative sensitivity of three polymerase chain reaction (PCR) assays for routine diagnosis of fresh bovine semen for the presence of BHV 1 Semen was collected twice a week up to 107 days post-infection (dpi). To reactivate latent virus, the bulls were treated with dexamethasone from 44 until 48 dpi. All samples were examined before and after cryopreservation treatment using a standard virus isolation (VI) method and three PCR assays: PCR A, PCR B and PCR C. PCR A and PCR C used an internal control plasmid DNA template and PCR B used the split sample method in order to control for false negative results. Of the 149 fresh semen samples that were tested, PCR A detected 45 positive, PCR B detected 39 positive and PCR C detected 66 positive, while virus was isolated from 22 samples. Of the 149 samples treated by cryopreservation, the virus was isolated from 13 samples and PCR C was positive in 21 samples. The results demonstrate that all three PCR assays are more sensitive than virus isolation, particularly during the later phases of infection.