Comparison of Five Diagnostic Methods for Detecting Bovine Viral Diarrhea Virus Infection in Calves

Diagnosis of bovine viral diarrhea virus: an overview of currently available methods

Bovine viral diarrhea virus (BVDV) is the causative agent of bovine viral diarrhea (BVD), which results in significant economic losses in the global cattle industry. Fortunately, various diagnostic methods available for BVDV have been established. They include etiological methods, such as virus isolation (VI); serological methods, such as enzyme-linked immunosorbent assay (ELISA), immunofluorescence assay (IFA), and immunohistochemistry (IHC); molecular methods, such as reverse transcription-polymerase chain reaction (RT-PCR), real-time PCR, digital droplet PCR (ddPCR), loop-mediated isothermal amplification (LAMP), recombinase polymerase amplification (RPA), and CRISPR-Cas system; and biosensors. This review summarizes the current diagnostic methods for BVDV, discussing their advantages and disadvantages, and proposes future perspectives for the diagnosis of BVDV, with the intention of providing valuable guidance for effective diagnosis and control of BVD disease.

Comparison of bovine viral diarrhea virus detection methods: Results of an international proficiency trial

Bovine viral diarrhea virus (BVDV), one of the most important infectious cattle diseases globally, is being combated in multiple countries. The main source for virus transmission within herds and especially to unaffected cattle farms are life-long persistently infected (PI), immunotolerant animals. Therefore, the early identification of PI calves is a major pillar of disease control programs. In addition, rapid and reliable virus identification is necessary to confirm the causative agent in acute clinical cases. Here, we initiated an international interlaboratory proficiency trial in order to evaluate BVDV detection methods. Four ear notch samples and four sera were provided to the participating veterinary diagnostic laboratories (n = 40). Two of the ear notches and two sera contained BVDV and two ear notches and one serum were negative for pestiviruses. The remaining serum was positive for the ovine border disease virus (BDV). The sample panel was analyzed by an ERNS-based ELISA for antigen detection, diverse real-time RT-PCR (RT-qPCR) assays and/or virus isolation. Occasionally, additional typing of the virus strains was performed by sequencing or specific antibody staining of the obtained cell culture isolates. While the antigen ELISA allowed reliable BVDV diagnostics, infectious virus could be isolated only in just under half of the attempts (43.33%). RT-qPCR enabled the sensitive detection of pestiviruses, though an impact of the extraction method on the resulting quantification cycle values was observed. In general, subsequent typing of the detected virus strains is required to differentiate BVDV from BDV infections. In conclusion, for BVDV identification in clinical cases or in the context of disease control, RT-qPCR methods or ERNS antigen ELISAs should be preferentially used.

An overview of the detection of bovine respiratory disease complex pathogens using immunohistochemistry: emerging trends and opportunities

The bovine respiratory disease complex (BRDC) is caused by a variety of pathogens, as well as contributing environmental and host-related risk factors. BRDC is the costliest disease for feedlot cattle globally. Immunohistochemistry (IHC) is a valuable tool for enhancing our understanding of BRDC given its specificity, sensitivity, cost-effectiveness, and capacity to provide information on antigen localization and immune response. Emerging trends in IHC include the use of multiplex IHC for the detection of coinfections, the use of digital imaging and automation, improved detection systems using enhanced fluorescent dyes, and the integration of IHC with spatial transcriptomics. Overall, identifying biomarkers for early detection, utilizing high-throughput IHC for large-scale studies, developing standardized protocols and reagents, and integrating IHC with other technologies are some of the opportunities to enhance the accuracy and applicability of IHC. We summarize here the various techniques and protocols used in IHC and highlight their current and potential role in BRDC research.

Diagnostics for Viral Pathogens in Veterinary Diagnostic Laboratories

Laboratory testing is one part of clinical diagnosis, and quick and reliable testing results provide important data to support treatment decision and develop control strategies. Clinical viral testing has been shifting from traditional virus isolation and electron microscopy to molecular polymerase chain reaction and point-of-care antigen tests. This shift in diagnostic methodology also means change from looking for infectious virions or viral particles to hunting viral antigens and genomes. With technological development, it is predicted that metagenomic sequencing will be commonly used in veterinary clinical diagnosis for unveiling the whole picture of microbes involved in diseases in the future.

First detection of emerging HoBi-like Pestivirus (BVD-3) among some persistently infected dairy cattle herds in Egypt

Bovine viral diarrhoea virus (BVDV) is a serious veterinary health concern worldwide. We conducted this study to determine the prevalence of persistent infections (PI) and identify the current strain among some dairy cattle herds in Egypt. A total of 240 serum samples were collected from six Egyptian provinces. Between 2019 and 2020, samples were tested by Enzyme linked immunosorbent assay (ELISA) for detection of PI animals, and then molecular characterization was performed. Six calves were found PI with a prevalence of 2.5% (6/240). Using molecular characterization, HoBi-like Pestivirus (BVD-3) was successfully identified in Egypt for the first time. Based on the BVD-3 reference strains on Genbank, the detected strains had an identity ranging from 98.8 to 99.6%. Partial nucleotide sequence of the 5'UTR gene for six tested samples was submitted to Genbank with accessions: OM324396, OM324397, OM324398, OM324399, OM3243100, and OM3243101.

Prevalence of Bovine Viral Diarrhea Virus in Ovine and Caprine Flocks: A Global Systematic Review and Meta-Analysis

Background: Bovine viral diarrhea virus (BVDV) is the causative agent of bovine viral diarrhea. It can infect cattle, sheep, pigs, and other animals, causing diarrhea, miscarriage, and stillbirth, among other symptoms, and it can result in huge economic losses to animal husbandry. There are reports on BVDV infection rates in sheep and goat herds from all over the world and this meta-analysis aimed to evaluate the prevalence of and risk factors for BVDV in sheep and goats. Results: Using the data of 41,297 sheep and goats in 24 countries/regions to calculate a comprehensive prevalence rate for BVDV. The overall prevalence of BVDV infection in sheep and goats was estimated to be 8.6% (95% CI: 5.2-12.7) by immunological methods and 7.3% (95% CI: 2.7-13.7) by molecular methods. Analysis by national income level revealed that prevalence is higher in middle-income countries than in high-income countries (P < 0.05). The study also compared prevalence rates by species of BVDV, sampling year, and test species, but did not find significant differences. Conclusion: This systematic review and meta-analysis is the first to determine the global prevalence of BVDV in ovine and caprine flocks. The prevalence of BVDV in sheep and goat populations varies from region to region, and the situation is not optimistic in some countries.

Eradication of Bovine Viral Diarrhoea (BVD) in Cattle in Switzerland: Lessons Taught by the Complex Biology of the Virus

Bovine viral diarrhoea virus (BVDV) and related ruminant pestiviruses occur worldwide and cause considerable economic losses in livestock and severely impair animal welfare. Switzerland started a national mandatory control programme in 2008 aiming to eradicate BVD from the Swiss cattle population. The peculiar biology of pestiviruses with the birth of persistently infected (PI) animals upon in utero infection in addition to transient infection of naïve animals requires vertical and horizontal transmission to be taken into account. Initially, every animal was tested for PI within the first year, followed by testing for the presence of virus in all newborn calves for the next four years. Prevalence of calves being born PI thus diminished substantially from around 1.4% to <0.02%, which enabled broad testing for the virus to be abandoned and switching to economically more favourable serological surveillance with vaccination being prohibited. By the end of 2020, more than 99.5% of all cattle farms in Switzerland were free of BVDV but eliminating the last remaining PI animals turned out to be a tougher nut to crack. In this review, we describe the Swiss BVD eradication scheme and the hurdles that were encountered and still remain during the implementation of the programme. The main challenge is to rapidly identify the source of infection in case of a positive result during antibody surveillance, and to efficiently protect the cattle population from re-infection, particularly in light of the endemic presence of the related pestivirus border disease virus (BDV) in sheep. As a consequence of these measures, complete eradication will (hopefully) soon be achieved, and the final step will then be the continuous documentation of freedom of disease.

Causes of Abortions in South American Camelids in Switzerland-Cases and Questionnaire

Over the last decade, South American camelids (SAC) have gained increasing popularity in Switzerland. They are used for several purposes such as fiber and meat production, as companion or guard animals and for trekking activities. The purpose of this study was to investigate the frequency and reasons for pregnancy loss and perinatal death in SAC herds. Within the scope of this study, early embryonic losses could not be identified, as pregnancy examinations by ultrasonography are not performed routinely. Aborted and stillborn fetuses were collected, necropsied and analyzed for infectious abortifacients. A nationwide survey among breeders was carried out. During a 1.5-year period, only eight cases of aborted or stillborn alpaca and llama (out of a population of 6550 animals) were reported by the breeders, and their causes were subsequently analyzed. In half of the cases, Coxiella burnetii was identified in the fetoplacental material. Abortions and stillbirths were reported to be rare in Swiss herds. As a conclusion, recording of embryonic losses through ultrasound training of veterinarians should be impaired and breeders motivated to have abortions and perinatal mortality examined. Special focus should be laid on C. burnetii due to its zoonotic risk.

Practices and opinions of New Zealand veterinarians regarding control of bovine viral diarrhoea

AIMS

To explore recommendations that New Zealand veterinarians make for diagnosing and managing bovine viral diarrhoea (BVD) in cattle herds under different clinical scenarios and their opinions towards potential barriers and opportunities for implementing BVD control programmes in New Zealand.

METHODS

A cross-sectional survey of registered veterinarians in New Zealand was conducted in 2019. Respondents were asked about the approaches they would use to manage BVD under different clinical scenarios as well as their opinions on national BVD control. A subset of veterinarians completed a more in-depth survey providing additional free-text responses on a range of different BVD topics. Descriptive statistics were provided for all quantitative study variables and the free-text responses were also analysed to generate further insights into veterinarians' perceptions towards BVD management.

RESULTS

The cross-sectional survey was completed by 101 of an estimated 870 (11.6%) cattle veterinarians. Thirty-five veterinarians completed the in-depth survey. There was wide variation in the BVD diagnostic testing and vaccination protocols that respondents recommended under different clinical scenarios. Annual bulk milk BVD testing was perceived as a valuable tool for initiating BVD discussions with dairy farmers. Respondents indicated that beef farmers were more difficult to engage in BVD control largely due to the logistical challenges of yarding cattle at the appropriate times to implement interventions, with many farmers only contacting veterinarians after experiencing a BVD outbreak Most respondents (91/101; 90%) believed it was possible to eradicate BVD from New Zealand, but cited lack of farmer awareness and poor compliance with management recommendations as significant barriers. The measure with the most support for inclusion in a compulsory national eradication programme was requiring farmers to declare the status of their animals prior to sale while the least supported measure was requiring farmers to double fence boundaries to prevent nose-to-nose contact with neighbouring stock. Although respondents highlighted the need for farmers and industry to support any national eradication programme in order for it to be successful, there was also recognition that veterinarians could be more pro-active in engaging with farmers particularly in discussions around the economics of BVD.

CONCLUSIONS AND CLINICAL RELEVANCE

While the survey respondents appeared to be highly supportive of BVD control, it was perceived that financial and logistical barriers existed that could impede farmer engagement. Further extension efforts may be needed to ensure that veterinarians are presenting clear and consistent recommendations about BVD management to farmers.Abbreviations: BVD: Bovine viral diarrhoea; NAIT: National Animal Identification and Tracing System; PI: Persistently infected.

Effect of calf age on bovine viral diarrhea virus tests

Bovine viral diarrhea virus (BVDV) causes significant economic loss in cattle. Detection of persistently infected (PI) animals is an important control measure, but persistence of maternal antibodies may result in false-negative test results. We assessed the sensitivity and specificity of 2 antigen ELISAs (Idexx BVDV Ag/Serum Plus and BVDV PI X2) and a reverse-transcription real-time PCR (RT-rtPCR; Idexx RealPCR BVDV) assay for detecting PI calves. Ear notch samples were collected from 1,030 calves ~3, 10, 24, and 38 d old (days 3, 10, 24, and 38). All day 38 samples were tested using 2 antigen ELISAs and RT-rtPCR, and any calf that tested positive by any of these tests was blood sampled at ~100 d old (day 100) for antigen and antibody testing by ELISA; samples collected on days 3, 10, and 24 were tested using the antigen ELISAs and PCR. Calves were defined as PI if they were test-positive on day 38 by either ELISA or PCR and were antigen-positive on day 100. Twenty-six calves were PCR BVDV test-positive and one was BVDV PI X2 ELISA-positive at day 38. Five calves were defined as PI, and all tested positive by ELISAs and RT-PCR assay on days 3, 10, and 24. The sensitivity and specificity were 100% for both antigen ELISAs and 96.7% and 100%, respectively, by RT-rtPCR. Test results were not affected by calf age, suggesting that testing for PI calves can be undertaken at any age.

An outbreak of abortions, stillbirths and malformations in a Spanish sheep flock associated with a bovine viral diarrhoea virus 2-contaminated orf vaccine

Bovine viral diarrhoea virus (BVDV) is a pestivirus that affects both cattle and sheep, causing an array of clinical signs, which include abortions and malformations in the offspring. Manufacturing of modified live virus (MLV) vaccines often includes the use of bovine-derived products, which implies a risk of contamination with viable BVDV. Recently, the circulation of a specific strain of BVDV 2b among Spanish sheep flocks, associated with outbreaks of abortions and malformations, and whose origin was not determined, has been observed. On February 2018, a MLV orf vaccine was applied to a 1,600 highly prolific sheep flock in the Northeast of Spain that included 550 pregnant ewes. In May 2018, during the lambing season, an unusual high rate (72.7%) of abortions, stillbirths, congenital malformations and neurological signs in the offspring was observed. It was estimated that about 1,000 lambs were lost. Three 1- to 3-day-old affected lambs and a sealed vial of the applied vaccine were studied. Lambs showed variable degrees of central nervous system malformations and presence of pestiviral antigen in the brain. Molecular studies demonstrated the presence of exactly the same BVDV 2b in the tissues of the three lambs and in the orf vaccine, thus pointing to a pestivirus contamination in the applied vaccine as the cause of the outbreak. Interestingly, sequencing at the 5'-untranslated region-(UTR) of the contaminating virus showed a complete match with the virus described in the previously reported outbreaks in Spain, thus indicating that the same contaminated vaccine could have also played a role in those cases. This communication provides a clear example of the effects of the application of this contaminated product in a sheep flock. The information presented here can be of interest in putative future cases of suspected circulation of this or other BVDV strains in ruminants.

Development of a quantitative risk assessment of bovine viral diarrhea virus and bovine herpesvirus-1 introduction in dairy cattle herds to improve biosecurity

A quantitative risk assessment model was developed to estimate the annual probability of introducing bovine viral diarrhea virus (BVDV) and bovine herpesvirus 1 (BoHV-1) at the farm level through animal movements. Data from 2017 official animal movements, biosecurity questionnaires, scientific literature, and expert opinion from field veterinarians were taken into consideration for model input parameters. Purchasing or introducing cattle, rearing replacement heifers offsite, showing cattle at competitions, sharing transport vehicles with other herds, and transporting cattle in vehicles that have not been cleaned and disinfected were considered in the model. The annual probability of introducing BVDV or BoHV-1 through infected animals was very heterogeneous between farms. The median likelihoods of BVDV and BoHV-1introduction were 12 and 9%, respectively. Farms that purchased cattle from within their region (i.e., local movements) and shared transport with other farms had a higher probability for BVDV and BoHV-1 introduction. This model can be a useful tool to support decision-making on biosecurity measures that should be prioritized to reduce the probability of introduction of these 2 diseases in dairy herds.

Evaluation of an investigative model in dairy herds with high calf perinatal mortality rates in Switzerland

The objective of this study was to evaluate an investigative model which encompassed the risk factors, incidence, timing and causes of perinatal mortality (PM) (0-48 h) on high risk dairy farms (PM of >5% in the previous year) in Switzerland. This pilot-study was carried out on 47 predominantly Holstein PM calves from 21 dairy farms, between September 2016 and January 2018. Gross pathological examinations of calves and placentae as well as histopathological examinations of internal organs and placental tissue were performed. Further investigations included microbiological examinations: broad-spectrum bacterial and fungal culture, detection of Chlamydia abortus, Coxiella burnetii, pathogenic Leptospira spp. and Neospora caninum by real-time PCR (qPCR) and of bovine viral diarrhoea virus (BVDV) by Ag-ELISA. Maternal blood samples were used for serology of bovine herpesvirus 1 (BHV-1), Brucella abortus, Chlamydia abortus, Coxiella burnetii and nine pathogenic leptospiral serovars and the evaluation of trace element status. A questionnaire was completed with the farmer, which included general farm characteristics and case-related data. Inbreeding coefficients (IC) were calculated for pure-bred matings. At the farm-level, the PM rate was 10.0% (5.3-28.2%) and at the cow-level, 11.5%. These values, from high-risk farms, were approximately five-times higher than the contemporary national bovine PM rate (2.3%) in Switzerland. The risk factors associated with these high PM rates were the self-selection of high risk herds, the high proportion of primiparae in these herds (45%) and the evidence of widespread pathogenic infections on these farms (exposure: 67% of herds, 53% of dams; infection: 57% of herds, 45% of calves). The majority (68.1%) of calves died intrapartum. The most commonly diagnosed initiating/ultimate cause of death (UCOD) was infection (34%) of which Coxiella burnetii was the most frequently detected pathogen, by antigen. The most frequently diagnosed proximate cause of death (PCOD) was asphyxia (44.7%), though multiple PCOD was also common (21.3%). This study was the first detailed investigation of bovine PM in Switzerland. Infectious causes were diagnosed more frequently than expected. While the findings from these high PM Swiss herds may have limited external validity, the investigative model adopted and the detailed research methodologies employed can be replicated and re-evaluated, respectively, in future studies on PM internationally.

Diagnostic studies of abortion in Danish cattle 2015-2017

Background

Abortion is a major source of economic losses in cattle breeding. Abortion occurs due to a wide range of causes, but infections are the most frequently diagnosed. However, establishing an aetiological diagnosis remains challenging due to the large variety of bacteria, protozoa, viruses, and fungi that have been associated with abortion in cattle. Economic restraints limit the range of diagnostic methods available for routine diagnostics, and decomposition of the conceptus or lack of proper fetal and/or maternal samples further restrict the diagnostic success. In this study, we report recent diagnostic findings from bovine abortions in Denmark, a country that has a large dairy sector and is free from most infectious agents causing epizootic abortion in cattle. The aims of the study were: (i) to identify infectious causes of bovine abortion in Denmark, (ii) to categorise the diagnostic findings based on the level of diagnostic certainty, and (iii) to assess the diagnostic rate. Due to economic restraints, only a limited panel of routine diagnostic methods were available. Placentas and/or fetuses from mid- to late-term abortions and stillbirths (n = 162) were submitted to the Danish National Veterinary Institute between January 2015 and June 2017. The aborted materials were examined macroscopically, histologically, and by bacterial culture. Maternal blood samples were tested for bovine viral diarrhoea virus (BVDV) antibodies.

Results

The likely aetiology of the abortion was diagnosed in 52 cases, resulting in a diagnostic rate of 33%. The most common cause was protozoal infection (19%) followed by infection with Trueperella pyogenes (3%), Staphylococcus aureus (2%), and non-haemolytic Escherichia coli (2%). Lesions in fetuses with a protozoal infection were consistent with neosporosis. In many cases (38%), inflammatory changes were found in the placenta and/or fetal organs but no specific aetiology was identified. Neither infection with Brucella spp. nor maternal BVDV antibodies were detected. The majority of submitting herds (92%) were each represented by fewer than three abortion cases over the study period.

Conclusions

Protozoal infection, most likely neosporosis, was the most commonly diagnosed cause of abortion and the only one associated with potential epizootic abortion events. Despite using a reduced number of diagnostic methods in comparison to other abortion studies, the diagnostic rate of this study was within the range reported in an earlier Danish study, as well as in recent international studies. The low number of submitted cases per herd and the sparse anamnestic information provided at submission hampered conclusions on the potential epizootic character of the abortion events in question.

Diagnostics in the context of an eradication program: Results of the German bovine viral diarrhea proficiency trial

Bovine viral diarrhea (BVD), one of the most important infectious diseases in cattle, causes major economic losses and significant impact on animal welfare worldwide. The major source for virus spread is persistently infected, immunotolerant calves and, therefore, their early identification is of utmost importance for disease prevention. Here, a ring trial was initiated to control the performance of diagnostic tests used in German regional laboratories in charge of the diagnostics within the country's BVD control program. A panel of five ear notch and five serum samples was provided for virological analysis. By an antigen ELISA, which was applied 26 times, the status of every sample was correctly identified in any case. In addition, a total of 54 real-time RT-PCR result sets was generated and also in most cases correctly classified. In addition to the virological test panel, a set of six sera and four milk samples was sent to the participating laboratories to be analyzed by serological methods. With serum neutralization tests, an excellent diagnostic sensitivity was achieved. However, one serum and both milk samples - positive for BVDV antibodies - repeatedly tested false negative by some of the used ELISA kits. All negative serum and milk samples were correctly identified by every commercial antibody ELISA. In conclusion, the BVDV proficiency test demonstrated that the used antigen/genome test systems allowed predominantly reliable diagnostics, while for four of the applied nine antibody ELISA kits adjustments are recommended.

Recommendations for the testing and control of bovine viral diarrhoea in New Zealand pastoral cattle production systems

Eradicating bovine viral diarrhoea (BVD) from cattle populations requires a clear approach for determining the epidemiological status of individual herds and implementing the appropriate control measures to ensure the transmission cycle is cost-effectively broken. This is particularly important in countries such as New Zealand where there is currently no coordinated national programme and the herd-level decisions to control BVD are left to the discretion of individual farmers and veterinarians. To ensure greater consistency in the information being delivered by different stakeholders, we review the epidemiology of BVD in the context of New Zealand pastoral production systems and provides a series of simplified recommendations for the future control of BVD in beef and dairy herds. Based on analysis of BVD test accession data from commercial diagnostic laboratories, it has been estimated that 40.6% of dairy herds and 45.6% of beef herds tested had positive results for antibodies to BVD virus. While BVD continues to remain widespread and under voluntary control in New Zealand, it is recommended that herds test all individual mixed-age cows and replacement heifers for BVD virus or antigen and remove persistently infected animals from the breeding population. All new breeding animals that have entered the herd either through purchase or birth should also be tested for BVD virus. Biosecurity risks should be managed by reducing contacts with other herds and implementing targeted vaccination programmes. All individual purchased cattle should be tested and confirmed negative for BVD virus before being moved onto the buyer's property, even if the herd of origin had a negative antibody-based screening test. Herds should continue annual antigen or virus testing of all calves as soon as possible after birth to identify any persistently infected animals.

Border disease in cattle

Within the family Flaviviridae, viruses within the genus Pestivirus, such as Border disease virus (BDV) of sheep, can cause great economic losses in farm animals. Originally, the taxonomic classification of pestiviruses was based on the host species they were isolated from, but today, it is known that many pestiviruses exhibit a broad species tropism. This review provides an overview of BDV infection in cattle. The clinical, hematological and pathological-anatomical findings in bovines that were transiently or persistently infected with BDV largely resemble those in cattle infected with the closely related pestivirus bovine viral diarrhoea virus (BVDV). Accordingly, the diagnosis of BDV infection can be challenging, as it must be differentiated from various pestiviruses in cattle. The latter is very relevant in countries with control programs to eradicate BVDV in Bovidae, as in most circumstances, pestivirus infections in sheep, which act as reservoir for BDV, are not included in the eradication scheme. Interspecies transmission of BDV between sheep and cattle occurs regularly, but BDV in cattle appears to be of minor general importance. Nevertheless, BDV outbreaks at farm or local level can be very costly.

Global knowledge gaps in the prevention and control of bovine viral diarrhoea (BVD) virus

The significant economic impacts of bovine viral diarrhoea (BVD) virus have prompted many countries worldwide to embark on regional or national BVD eradication programmes. Unlike other infectious diseases, BVD control is highly feasible in cattle production systems because the pathogenesis is well understood and there are effective tools to break the disease transmission cycle at the farm and industry levels. Coordinated control approaches typically involve directly testing populations for virus or serological screening of cattle herds to identify those with recent exposure to BVD, testing individual animals within affected herds to identify and eliminate persistently infected (PI) cattle, and implementing biosecurity measures such as double-fencing shared farm boundaries, vaccinating susceptible breeding cattle, improving visitor and equipment hygiene practices, and maintaining closed herds to prevent further disease transmission. As highlighted by the recent DISCONTOOLS review conducted by a panel of internationally recognized experts, knowledge gaps in the control measures are primarily centred around the practical application of existing tools rather than the need for creation of new tools. Further research is required to: (a) determine the most cost effective and socially acceptable means of applying BVD control measures in different cattle production systems; (b) identify the most effective ways to build widespread support for implementing BVD control measures from the bottom-up through farmer engagement and from the top-down through national policy; and (c) to develop strategies to prevent the reintroduction of BVD into disease-free regions by managing the risks associated with the movements of animals, personnel and equipment. Stronger collaboration between epidemiologists, economists and social scientists will be essential for progressing efforts to eradicate BVD from more countries worldwide.

Limited added value of fungal ITS amplicon sequencing in the study of bovine abortion

Bovine mycotic abortion is sporadic and caused by different ubiquitous and opportunistic fungi. Recently, a broad spectrum of bacterial opportunists involved in bovine abortion was revealed by 16S rRNA gene amplicon sequencing. We hypothesized that fungal organisms potentially involved in bovine abortion also might remain undetected by conventional culture. In this retrospective study, we therefore applied fungal internal transcribed spacer 2 (ITS2) region amplicon sequencing to 74 cases of bovine abortion submitted to our diagnostic service. The investigation was complemented by fungal culture and, retrospectively, by data from bacteriological, virological and parasitological analyses and histopathological examination of placentas. Fungal DNA was found in both the placentas and abomasal contents, with 92 fungal genera identified. In 18 cases, >75% of the reads belonged to one specific fungal genus: Candida (n = 7), Malassezia (n = 4), Cryptococcus (n = 3), unidentified Capnodiales (n = 3), Actinomucor (n = 1), Cystofilobasidium (n = 1), Penicillium (n = 1), Verticillum (n = 1) and Zymoseptoria (n = 1) with one case harboring two different genera. By culture, in contrast, fungal agents were detected in only 6 cases. Inflammatory and/or necrotizing lesions were found in 27/40 histologically assessed placentas. However, no lesion-associated fungal structures were detected in HE- and PAS-stained specimens. Complementary data revealed the presence of one or more non-fungal possible abortifacient: Chlamydiales, Coxiella burnetii, Leptospira spp., Campylobacter fetus subsp. fetus, Streptococcus uberis, Escherichia coli, Streptococcus pluranimalium, Bacillus licheniformis, Campylobacter fetus subsp. fetus, Serratia marcescens, Trueperella pyogenes, Schmallenbergvirus, Neospora caninum. The mycobiota revealed by sequencing did not differ between cases with or without a possible infectious etiology. Our study suggests that amplicon sequencing of the ITS2 region from DNA isolated from bovine abortion does not provide additional information or new insight into mycotic abortion and without complementary analyses may easily lead to a false interpretation of the role of fungal organisms in bovine abortion.

Epidemiological surveillance of bovine viral diarrhea and rift valley fever infections in camel

Aim:

This study was designed to investigate the current epidemiological situation of bovine viral diarrhea virus (BVDV) and rift valley fever virus (RVFV) infection of camels originating from Sudan “smuggler” and Egypt as part of our future plan for a national surveillance program in Egyptian provinces, which will aid in establishment of control strategy for animal diseases.

Materials and Methods:

This investigation was accomplished using serological diagnostic and molecular biology techniques. A total number of 200 blood samples were collected from camel (120 originated from Sudan “smuggler” and 80 from local breed) and were subjected for testing both BVDV and RVFV occurrence with different age and sex.

Results:

Sixty-six of the 200 camels (33%) were positive for BVDV antibodies, and 44 (22%) for BVDV antigen (Ag), and 27 of the 200 camels (13.5%) were positive for RVFV immunoglobulin G (IgG) antibodies. On the other hand, the seroprevalence of BVDV for antibodies (47.5%), Ag (31.6%), and RVFV IgG antibodies (16.6%) was higher in camel originated from Sudan “smuggler” than of local breed which was 11.2% for BVDV antibodies and 7.5% for BVDV Ag, while it was 8.7% for RVFV IgG antibodies. The incidence of BVDV antibodies, Ag, and RVFV IgG antibodies was the highest in male, up to 9 years of age. The frequency of positive cases was significantly different according to the origin of samples and sex and age of camel for BVDV and RVFV. In addition, seven serologically positive samples for BVDV and five serologically positive samples for RVFV were submitted as a buffy coat for molecular detection by one-step – reverse transcription polymerase chain reaction (RT-PCR). The results demonstrated that three samples were positive for BVDV of camel originated from Sudan (smuggler), while no RVFV Ag was detected in all five samples. Sequencing and phylogenetic analysis of the amplicons obtained from positive RT-PCR samples (three samples) indicated 100% nucleotide homology with Sudan strain 2015 except only one (missense point mutation) by substitution of A to T at position 345 that changed the coded amino acids from T (Threonine) to S (Serine) at residue 115.

Conclusion:

Camels act as risk animals for the introduction of many infectious diseases from Sudan to Egypt, especially transboundary animal diseases, so strict quarantine measures should be taken during importation of live animals from Sudan to prevent the spread of such diseases.

A meta-analysis of bovine viral diarrhoea virus (BVDV) prevalences in the global cattle population

A random effect meta-analysis was performed to estimate the worldwide pooled bovine viral diarrhoea virus (BVDV) prevalences of persistently infected (PI), viraemic (VI) and antibody-positive (AB) animals and herds. The meta-analysis covered 325 studies in 73 countries that determined the presence or absence of BVDV infections in cattle from 1961 to 2016. In total, 6.5 million animals and 310,548 herds were tested for BVDV infections in the global cattle population. The worldwide pooled PI prevalences at animal level ranged from low (≤0.8% Europe, North America, Australia), medium (>0.8% to 1.6% East Asia) to high (>1.6% West Asia). The PI and AB prevalences in Europe decreased over time, while BVDV prevalence increased in North America. The highest mean pooled PI prevalences at animal level were identified in countries that had failed to implement any BVDV control and/or eradication programmes (including vaccination). Our analysis emphasizes the need for more standardised epidemiological studies to support decision-makers implementing animal health policies for non-globally-regulated animal diseases.

Spatial and risk factor analysis of bovine viral diarrhoea (BVD) virus after the first-year compulsory phase of BVD eradication programme in Northern Ireland

Bovine viral diarrhoea virus (BVDV) causes bovine viral diarrhoea (BVD), which is a contagious pathogen that can have a significant economic impact on cattle industries. In Northern Ireland (NI), the compulsory phase of a BVD eradication programme was implemented in 2016. The aim of this retrospective population based study was to utilize herd-level data after the first year of the compulsory phase (March 2016-March 2017) to determine the spatial distribution and variation of BVDV, to identify clusters of infection, and to quantify some risk factors associated with BVD in NI. Global spatial clustering (autocorrelation) and local spatial hot-spot analyses were used to specify the clustering areas (hot- and cold-spot). A suite of multivariable logistic analyses was performed to estimate the associations of spatial and non-spatial factors (relating to herd characteristics) with the risk of being a BVDV positive herd. Final models were compared by evaluating the model fit and the ability to account for spatial autocorrelation in the study area. There were 17,186 herds included in the analysis. The herd-level prevalence of BVDV was 11.31%. Significant spatial clustering of BVDV positive herds was presented in the central region of NI. A mixed effects logistic model, with a spatial random effect term, was considered the best model. The final model showed that a positive BVDV status during the voluntary phase prior to the compulsory phase started (OR = 2.25; CI 95% = 1.85-2.73), larger herd size (OR = 6.19; CI 95% = 5.22-7.34 for herd size > 100 animals) and a larger number of positive nearest neighbours within 4 km radius (OR = 1.24; CI 95% = 1.05-1.47 for 8-9 neighbours and OR = 1.41; CI 95% = 1.20-1.65 for 10-12 neighbours) were significantly related to the risk of a herd being tested positive for BVDV. The clear spatial pattern from the local spatial clustering analyses could be used for targeted surveillance and control measures by focusing on the central region of NI.

Rapid Veterinary Diagnosis of Bovine Reproductive Infectious Diseases from Semen Using Paper-Origami DNA Microfluidics

The health and well-being of cattle is an important issue in maintaining and increasing global agricultural output. In dairy production within low and middle income countries (LMICs), there is a significant biosensing challenge in detecting sexually transmitted infection (STI) pathogens during animal husbandry, due in part to difficulties associated with the limited infrastructure for veterinary medicine. Here we demonstrate low-cost, multiplexed, and sample-to-answer paper-origami tests for the detection of three bovine infectious reproductive diseases in semen samples, collected at a test site in rural India. Pathogen DNA from one viral pathogen, bovine herpes virus-1 (BoHV-1), and two bacteria (Brucella and Leptospira) was extracted, amplified (using loop-mediated isothermal amplification, LAMP), and detected fluorescently, enabling <1 pg (∼ from 115 to 274 copies per reaction) of target genomic DNA to be measured. Data was collected as a fluorescence signal either visually, using a low-cost hand-held torch, or digitally with a mobile-phone camera. Limits of detection and sensitivities of the paper-origami device for the three pathogens were also evaluated using pathogen-inoculated semen samples and were as few as 50 Leptospira organisms, 50 CFU Brucella, and 1 TCID₅₀ BoHV-1. Semen samples from elite bulls at a germplasm center were also tested in double-blind tests, as a demonstrator for a low-cost, user-friendly point-of-care sensing platform, for in-the-field resource-limited regions. The sensors showed excellent levels of sensitivity and specificity, and for the first time a demonstrated ability of the application of paper microfluidics devices for the diagnosis multiple infectious diseases from semen samples.

Border Disease Virus Infection of Bovine Placentas

Subsequent to a previous study of border disease virus (BDV) horizontal transmission from a persistently BDV-infected calf to 6 seronegative pregnant heifers, the heifers were slaughtered 60 days after exposure to the infected calf, and their fetuses and placentas were examined. Immunohistochemical examination of fetal organs and placenta showed positive labeling of moderate intensity for pestivirus antigen in 3 of 6 heifers. BDV infection in these 3 animals was confirmed by the detection of BDV RNA in different organs using reverse transcription quantitative polymerase chain reaction. In the placenta, the positive cells were visualized mostly on the fetal side. In those 3 heifers that harbored an infected fetus, the placental tissue in the placentome region showed a moderate to severe mononuclear and fibrosing placentitis and, in severe cases, necrotic areas. The inflammatory population was composed predominantly of T and B cells, a substantial number of macrophages, and, to a lesser extent, plasma cells. This is a novel report of placentitis in persistently BDV-infected fetuses from pregnant heifers that became acutely infected by cohousing with a calf persistently infected with BDV, which extends previous reports on bovine viral diarrhea virus-infected and BDV-infected cattle and sheep, respectively.

Six Years (2011-2016) of Mandatory Nationwide Bovine Viral Diarrhea Control in Germany-A Success Story

Bovine viral diarrhea (BVD) is one of the most important infectious diseases in cattle, causing major economic losses worldwide. Therefore, control programs have been implemented in several countries. In Germany, an obligatory nationwide eradication program has been in force since 2011. Its centerpiece is the detection of animals persistently infected (PI) with BVD virus, primarily based on the testing of ear tissue samples of all newborn calves for viral genome or antigen, and their removal from the cattle population. More than 48,000 PI animals have so far been detected and removed. Between the onset of the program and the end of 2016, the prevalence of these animals among all newborn calves decreased considerably, from 0.5% to less than 0.03%. The number of cattle holdings with PI animals likewise decreased from 3.44% in 2011 to only 0.16% in 2016. Since a large number of naïve, fully susceptible animals are now confronted with BVD virus, which is still present in the German cattle population, the challenge of the coming years will be the identification of remaining PI animals as quickly and efficiently as possible, and the efficient protection of BVD-free farms from reinfection.

Assessment of listing and categorisation of animal diseases within the framework of the Animal Health Law (Regulation (EU) No 2016/429): bovine viral diarrhoea (BVD)

Bovine viral diarrhoea (BVD) has been assessed according to the criteria of the Animal Health Law (AHL), in particular criteria of Article 7 on disease profile and impacts, Article 5 on the eligibility of BVD to be listed, Article 9 for the categorisation of BVD according to disease prevention and control rules as in Annex IV and Article 8 on the list of animal species related to BVD. The assessment has been performed following a methodology composed of information collection and compilation, expert judgement on each criterion at individual and, if no consensus was reached before, also at collective level. The output is composed of the categorical answer, and for the questions where no consensus was reached, the different supporting views are reported. Details on the methodology used for this assessment are explained in a separate opinion. According to the assessment performed, BVD can be considered eligible to be listed for Union intervention as laid down in Article 5(3) of the AHL. The disease would comply with the criteria as in Sections 4 and 5 of Annex IV of the AHL, for the application of the disease prevention and control rules referred to in points (d) and (e) of Article 9(1). The assessment here performed on compliance with the criteria as in Section 3 of Annex IV referred to in point (c) of Article 9(1) is inconclusive. The animal species to be listed for BVD according to Article 8(3) criteria are mainly species of the families Bovidae, Cervidae and Camelidae as susceptible species and several mammalian species as reservoirs.

Virus detection by PCR following vaccination of naive calves with intranasal or injectable multivalent modified-live viral vaccines

We evaluated duration of PCR-positive results following administration of modified-live viral (MLV) vaccines to beef calves. Twenty beef calves were randomly assigned to either group 1 and vaccinated intranasally with a MLV vaccine containing bovine alphaherpesvirus 1 (BoHV-1), bovine respiratory syncytial virus (BRSV), and bovine parainfluenza virus 3 (BPIV-3), or to group 2 and vaccinated subcutaneously with a MLV vaccine containing bovine viral diarrhea virus 1 and 2 (BVDV-1, -2), BoHV-1, BRSV, and BPIV-3. Deep nasopharyngeal swabs (NPS) and transtracheal washes (TTW) were collected from all calves, and whole blood was collected from group 2 calves and tested by PCR. In group 1, the proportions of calves that tested PCR-positive to BVDV, BoHV-1, BRSV, and BPIV-3 on any sample at any time were 0%, 100%, 100%, and 10%, respectively. In group 1 calves, 100% of calves became PCR-positive for BoHV-1 by day 3 post-vaccination and 100% of calves became PCR-positive for BRSV by day 7 post-vaccination. In group 2, the proportions of calves that tested positive to BVDV, BoHV-1, BRSV, and BPIV-3 on any sample at any time were 50%, 40%, 10%, and 0%, respectively. All threshold cycle (Ct) values were >30 in group 2 calves, irrespective of virus; however, Ct values <25 were observed in group 1 calves from PCR-positive results for BoHV-1 and BRSV. All calves were PCR-negative for all viruses after day 28. Following intranasal MLV viral vaccination, PCR results and Ct values for BRSV and BoHV-1 suggest that attempts to differentiate vaccine virus from natural infection is unreliable.

Survey for detecting persistently infected cattle with bovine viral diarrhea in Japan

To establish effective and efficient control measures for bovine viral diarrhea (BVD) in Japan, a pilot survey on persistently infected (PI) animals in dairy farms was conducted. A total of 5,949 cattle from 79 farms in 11 prefectures were tested; seven cattle in six farms were identified as PI animals. The proportion of farms with PI animals in Japan was calculated as 7.6% (95% confidence interval: 3.1–16.4%), and proportion of cattle tested as PI animals was 0.12% (95% confidence interval: 0.05–0.25%). The presence of only one or two animals in PI positive farms suggested the application of screening tests covering almost all cattle in each farm using pooled serum or bulk milk could be effective for implementing a large-scale survey for detecting PI animals.

Production of Monoclonal Antibody Against Recombinant Polypeptide From the Erns Coding Region of the Bovine Viral Diarrhea Virus

Background:

Bovine viral diarrhea (BVD) is an economically important cattle disease with a worldwide distribution. Detection and elimination of animals persistently infected (PI) with bovine viral diarrhea virus (BVDV) is essential for the control of BVD and eradication of BVDV. There are usually no pathognomonic clinical signs of BVDV infection. Diagnostic investigations therefore rely on laboratory-based detection of the virus, or virus-induced antigens or antibodies.

Objectives:

Erns as an immunogenic protein of BVDV, is genetically and antigenically conserved among different isolates and therefore, is a candidate antigen for development of the enzyme linked immunosorbent assay (ELISA) for serological studies or identification of PI animals. The aim of this study was to produce a monoclonal antibody (MAb) against recombinant Erns.

Materials and Methods:

For this purpose, recombinant maltose-binding protein (MBP)-Erns protein was expressed in Escherichia coli and purified using amylose resin chromatography column and used as an antigen in MAb production. Spleen cells of the immunized mice with the recombinant antigen were fused with SP2/0 myeloma cells. Next, culture supernatants of primary clones of fused cells were screened by indirect ELISA. After three rounds of cloning, the reactivity of the MAbs with recombinant and natural antigen was established by Western blotting.

Results:

Based on our results, MAb against recombinant Erns was produced and reacted successfully with recombinant and natural antigens.

Conclusions:

With regards to the role of Erns in the identification of PI animals, it appears that Erns recombinant antigen and the specific monoclonal antibodies produced against it may be suitable for developing BVDV laboratory diagnostic assays.

Cross-priming amplification for detection of bovine viral diarrhoea virus species 1 and 2

AIMS

The aim of the study was the development of cross-priming amplification for ubiquitous detection of bovine viral diarrhoea virus (BVDV) species 1 and 2.

METHODS AND RESULTS

Three and five specific primers, respectively, for the detection of BVDV-1 and BVDV-2, were designed on the basis of the sequences of the 5'UTR region. Incubation temperature and reaction time were determined. The optimal incubation conditions using water bath were 63°C for 75 min. Reverse transcription step (RT) was not required. The results were visualized under UV-light as a bright yellow fluorescence in positive samples. Additional method for results interpretation was agarose gel electrophoresis. Positive samples showed the presence of ladder-like banding patterns, formed by harpin-like cross-priming amplification (CPA) products. Sensitivity of CPA was compared with conventional RT-PCR and real-time RT-PCR. The CPA detection limit was 3500 copies for BVDV-1 and 80000 copies for BVDV-2 per reaction. For RT-PCR it was 350 and 80 copies for BVDV-1 and BVDV-2, respectively, and for real-time RT-PCR it was 35 copies for BVDV-1 and 80 copies for BVDV-2. The sensitivity of the developed method is sufficient to detect persistently infected (PI) animals. Positive results were found in 24 of 25 BVDV isolates belonging to species 1 and 2. Additionally, one false-negative result for BVDV-2 was detected. There were no false-positive results in negative samples and in the negative control. Both sets of primers used for the detection of BVDV-1 and BVDV-2 were not able to detect atypical pestiviruses. CPA positive results were confirmed by RT-PCR and real-time RT-PCR.

CONCLUSIONS

CPA is a rapid method for the detection of BVDV-1 and BVDV-2 in field samples from PI animals.

SIGNIFICANCE AND IMPACT OF STUDY

This is the first report on the application of the CPA method for the detection of BVDV.

Transmission of border disease virus from a persistently infected calf to seronegative heifers in early pregnancy

Background

This study describes the transmission of border disease virus (BDV) from a persistently infected calf to seronegative heifers in early pregnancy, resulting in persistently infected fetuses. On day 50 of pregnancy (= day 0 of the infection phase), six heifers were co-housed in a free stall with a bull calf persistently infected with BDV (pi BVD) for 60 days. The heifers underwent daily clinical examination, and blood samples were collected regularly for detection of pestiviral RNA and anti-pestivirus antibodies. After day 60 (= day 110 of pregnancy), the heifers were slaughtered, and the fetuses and placentae underwent post-mortem and immunohistochemical examination and RT-PCR for viral RNA detection.

Results

Three heifers had mild viraemia from day 8 to day 14, and by day 40 all heifers had pestivirus antibodies identified as anti-BDV antibodies in the serum neutralisation test. The placenta of the three viraemic heifers had histological evidence of inflammation, and fetal organs from these heifers were positive for pestivirus antigen by immunohistochemical examination and for BD viral RNA by RT-PCR and sequencing. Thus, co-housing of heifers in early pregnancy with a pi-BDV calf led to seroconversion in all heifers and persistent fetal infection in three.

Conclusions

Considering that pi-BDV cattle can infect other cattle and lead to persistent infection of the fetus in pregnant cows, BDV should not be ignored in the context of the mandatory BVDV eradication and monitoring program. This strongly suggests that BDV should be taken into account in BVD eradication and control programs.

Epidemiology of bovine viral diarrhoea among tropical small holder dairy units in Kerala, India

Prevalence of bovine viral diarrhoea among 385 dairy cattle reared under a small holder system in Trichur District of Kerala State in India was determined through an ELISA targeting antibodies against p80-p125 non-structural protein of the virus. Prevalence was 24.7% among the total population, but was higher (52%) when 85 animals having infertility problems alone were considered. Significant serum biochemistry differences between animals could be noticed only in total protein, globulin and phosphorous, all of which were low in seropositive animals. All animals which were seronegative for antibodies were screened by another ELISA targeting the E(rns) protein of the viral nucleocapsid to detect persistently infected (PI) animals. The single, positive animal had only a transient period of antigens in the blood, indicating absence of PI animals in the study population. High prevalence of the disease in isolated small holder units even in the absence of PI animals is discussed in view of identifying the common source of infection and initiating control measures.

Generation of calves persistently infected with HoBi-like pestivirus and comparison of methods for detection of these persistent infections

The identification and elimination of persistently infected (PI) cattle are the most effective measures for controlling bovine pestiviruses, including bovine viral diarrhea virus (BVDV) and the emerging HoBi-like viruses. Here, colostrum-deprived calves persistently infected with HoBi-like pestivirus (HoBi-like PI calves) were generated and sampled (serum, buffy coat, and ear notches) on the day of birth (DOB) and weekly for 5 consecutive weeks. The samples were subjected to diagnostic tests for BVDV--two reverse transcriptase PCR (RT-PCR) assays, two commercial real-time RT quantitative PCR (RT-qPCR), two antigen capture enzyme-linked immunosorbent assays (ACE), and immunohistochemistry (IHC)--and to HoBi-like virus-specific RT-PCR and RT-qPCR assays. The rate of false negatives varied among the calves. The HoBi-like virus-specific RT-PCR detected HoBi-like virus in 83%, 75%, and 87% of the serum, buffy coat, and ear notch samples, respectively, while the HoBi-like RT-qPCR detected the virus in 83%, 96%, and 62%, respectively. In comparison, the BVDV RT-PCR test had a higher rate of false negatives in all tissue types, especially for the ear notch samples (missing detection in at least 68% of the samples). The commercial BVDV RT-qPCRs and IHC detected 100% of the ear notch samples as positive. While ACE based on the BVDV glycoprotein E(rns) detected infection in at least 87% of ear notches, no infections were detected using NS3-based ACE. The BVDV RT-qPCR, ACE, and IHC yielded higher levels of detection than the HoBi-like virus-specific assays, although the lack of differentiation between BVDV and HoBi-like viruses would make these tests of limited use for the control and/or surveillance of persistent HoBi-like virus infection. An improvement in HoBi-like virus tests is required before a reliable HoBi-like PI surveillance program can be designed.

Laboratory diagnosis of ruminant abortion in Europe

Abortion in ruminants is a major cause of economic loss worldwide, and the management and control of outbreaks is important in limiting their spread, and in preventing zoonotic infections. Given that rapid and accurate laboratory diagnosis is central to controlling abortion outbreaks, the submission of tissue samples to laboratories offering the most appropriate tests is essential. Direct antigen and/or DNA detection methods are the currently preferred methods of reaching an aetiological diagnosis, and ideally these results are confirmed by the demonstration of corresponding macroscopic and/or histopathological lesions in the fetus and/or the placenta. However, the costs of laboratory examinations may be considerable and, even under optimal conditions, the percentage of aetiological diagnoses reached can be relatively low. This review focuses on the most commonly occurring and important abortifacient pathogens of ruminant species in Europe highlighting their epizootic and zoonotic potential. The performance characteristics of the various diagnostic methods used, including their specific advantages and limitations, are discussed.

Persistent infections after natural transmission of bovine viral diarrhoea virus from cattle to goats and among goats

Bovine viral diarrhoea virus (BVDV) is an economically important pathogen of cattle worldwide. Infection of a pregnant animal may lead to persistent infection of the foetus and birth of a persistently infected (PI) calf that sheds the virus throughout its life. However, BVD viruses are not strictly species specific. BVDV has been isolated from many domesticated and wild ruminants. This is of practical importance as virus reservoirs in non-bovine hosts may hamper BVDV control in cattle. A goat given as a social companion to a BVDV PI calf gave birth to a PI goat kid. In order to test if goat to goat infections were possible, seronegative pregnant goats were exposed to the PI goat. In parallel, seronegative pregnant goats were kept together with the PI calf. Only the goat to goat transmission resulted in the birth of a next generation of BVDV PI kids whereas all goats kept together with the PI calf aborted. To our knowledge, this is the first report which shows that a PI goat cannot only transmit BVD virus to other goats but that such transmission may indeed lead to the birth of a second generation of PI goats. Genetic analyses indicated that establishment in the new host species may be associated with step-wise adaptations in the viral genome. Thus, goats have the potential to be a reservoir for BVDV. However, the PI goats showed growth retardation and anaemia and their survival under natural conditions remains questionable.

Apoptosis in Bovine viral diarrhea virus (BVDV)-induced mucosal disease lesions: a histological, immunohistological, and virological investigation

Cattle persistently infected with a noncytopathic Bovine viral diarrhea virus (BVDV) are at risk of developing fatal "mucosal disease" (MD). The authors investigated the role of various apoptosis pathways in the pathogenesis of lesions in animals suffering from MD. Therefore, they compared the expression of caspase-3, caspase-8, caspase-9, and Bcl-2L1 (Bcl-x) in tissues of 6 BVDV-free control animals, 7 persistently infected (PI) animals that showed no signs of MD (non-MD PI animals), and 11 animals with MD and correlated the staining with the localization of mucosal lesions. Caspase-3 and -9 staining were markedly stronger in MD cases and were associated with mucosal lesions, even though non-MD PI animals and negative controls also expressed caspase-9. Conversely, caspase-8 was not elevated in any of the animals analyzed. Interestingly, Bcl-x also colocalized with mucosal lesions in the MD cases. However, Bcl-x was similarly expressed in tissues from all 3 groups, and thus, its role in apoptosis needs to be clarified. This study clearly illustrates ex vivo that the activation of the intrinsic, but not the extrinsic, apoptosis pathway is a key element in the pathogenesis of MD lesions observed in cattle persistently infected with BVDV. However, whether direct induction of apoptosis in infected cells or indirect effects induced by the virus are responsible for the lesions observed remains to be established.

An economic model to evaluate the mitigation programme for bovine viral diarrhoea in Switzerland

Economic analyses are indispensable as sources of information to help policy makers make decisions about mitigation resource use. The aim of this study was to conduct an economic evaluation of the Swiss national mitigation programme for bovine viral diarrhoea virus (BVDV), which was implemented in 2008 and concludes in 2017. The eradication phase of the mitigation programme comprised testing and slaughtering of all persistently infected (PI) animals found. First, the whole population was antigen tested and all PI cattle removed. Since October 2008, all newborn calves have been subject to antigen testing to identify and slaughter PI calves. All mothers of PI calves were retested and slaughtered if the test was positive. Antigen testing in calves and elimination of virus-carriers was envisaged to be conducted until the end of 2011. Subsequently, a surveillance programme will document disease freedom or detect disease if it recurs. Four alternative surveillance strategies based on antibody testing in blood from newborn calves and/or milk from primiparous cows were proposed by Federal Veterinary Office servants in charge of the BVDV mitigation programme. A simple economic spreadsheet model was developed to estimate and compare the costs and benefits of the BVDV mitigation programme. In an independent project, the impact of the mitigation programme on the disease dynamics in the population was simulated using a stochastic compartment model. Mitigation costs accrued from materials, labour, and processes such as handling and testing samples, and recording results. Benefits were disease costs avoided by having the mitigation programme in place compared to a baseline of endemic disease equilibrium. Cumulative eradication costs and benefits were estimated to determine the break-even point for the eradication component of the programme. The margin over eradication cost therefore equalled the maximum expenditure potentially available for surveillance without the net benefit from the mitigation programme overall becoming zero. Costs of the four surveillance strategies and the net benefit of the mitigation programme were estimated. Simulations were run for the years 2008-2017 with 20,000 iterations in @Risk for Excel. The mean baseline disease costs were estimated to be 16.04 m CHF (1 Swiss Franc, CHF=0.73 € at the time of analysis) (90% central range, CR: 14.71-17.39 m CHF) in 2008 and 14.89 m CHF (90% CR: 13.72-16.08 m CHF) in 2009. The break-even point was estimated to be reached in 2012 and the margin over eradication cost 63.15m CHF (90% CR: 53.72-72.82 m CHF). The discounted cost for each surveillance strategy was found to be smaller than the margin, so the mitigation programme overall is expected to have a positive net economic benefit irrespective of the strategy adopted. For economic efficiency, the least cost surveillance alternative must be selected.

Implementation of immunohistochemistry on frozen ear notch tissue samples in diagnosis of bovine viral diarrhea virus in persistently infected cattle

Background

Bovine viral diarrhea is a contagious disease of domestic and wild ruminants and one of the most economically important diseases in cattle. Bovine viral diarrhea virus belongs to the genus Pestivirus, within the family Flaviviridae. The identification and elimination of the persistently infected animals from herds is the initial step in the control and eradication programs. It is therefore necessary to have reliable methods for diagnosis of bovine viral diarrhea virus. One of those methods is immunohistochemistry. Immunohistochemistry on formalin fixed, paraffin embedded tissue is a routine technique in diagnosis of persistently infected cattle from ear notch tissue samples. However, such technique is inappropriate due to complicated tissue fixation process and it requires more days for preparation. On the contrary, immunohistochemistry on frozen tissue was usually applied on organs from dead animals. In this paper, for the first time, the imunohistochemistry on frozen ear notch tissue samples was described.

Findings

Seventeen ear notch tissue samples were obtained during the period 2008-2009 from persistently infected cattle. Samples were fixed in liquid nitrogen and stored on -20°C until testing. Ear notch tissue samples from all persistently infected cattle showed positive results with good section quality and possibility to determinate type of infected cells.

Conclusions

Although the number of samples was limited, this study indicated that immunohistochemistry on formalin fixed paraffin embedded tissue can be successfully replaced with immunohistochemistry on frozen ear notch tissue samples in diagnosis of persistently infected cattle.

The diagnosis and prevalence of persistent infection with bovine viral diarrhoea virus in South African feedlot cattle

Bovine viral diarrhoea virus (BVDV) infection is an important viral infection affecting the cattle industry today. The prevalence of this infection in South African feedlots is unknown. Ear notch biopsies were collected from chronic poor doers and animals that appeared unthrifty upon entering feedlots, as well as animals entering the hospital pen with respiratory disease for the first time. A total of 1690 samples were collected: 1074 from the former category and 616 from the latter. A routine immunohistochemistry staining protocol showed that 49 animals tested positive, of which 43 (4%) came from the feedlot entry group and six (1%) from the hospitalised group. The prevalence of persistently infected cattle from this selected, nonrandom sample entering six large South African feedlots was found to be 2.9%, which is higher than the international rule of thumb that 0.5% of all cattle entering feedlots are persistently infected. There was no clear correlation between persistent infection and respiratory disease. Serum samples were also collected when possible and 10 positive cases were found. Results from enzyme-linked immunosorbent assays for antigen and antibody performed on these sera correlated well with those from the immunohistochemistry staining method in six cases, but in four cases the animals tested falsely positive owing to nonspecific staining. Immunohistochemistry staining on ear notch biopsies is thus a reliable diagnostic method to identify persistently infected animals with BVDV, but the pathologist should be aware of nonspecific positive staining.

Development of one-step SYBR Green real-time RT-PCR for quantifying bovine viral diarrhea virus type-1 and its comparison with conventional RT-PCR

Background

Bovine viral diarrhea virus (BVDV) is a worldwide pathogen in cattle and acts as a surrogate model for hepatitis C virus (HCV). One-step real-time fluorogenic quantitative reverse transcription polymerase chain reaction (RT-PCR) assay based on SYBR Green I dye has not been established for BVDV detection. This study aims to develop a quantitative one-step RT-PCR assay to detect BVDV type-1 in cell culture.

Results

One-step quantitative SYBR Green I RT-PCR was developed by amplifying cDNA template from viral RNA and using in vitro transcribed BVDV RNA to establish a standard curve. The assay had a detection limit as low as 100 copies/ml of BVDV RNA, a reaction efficiency of 103.2%, a correlation coefficient (R²) of 0.995, and a maximum intra-assay CV of 2.63%. It was 10-fold more sensitive than conventional RT-PCR and can quantitatively detect BVDV RNA levels from 10-fold serial dilutions of titrated viruses containing a titer from 10^-1 to 10^-5 TCID₅₀, without non-specific amplification. Melting curve analysis showed no primer-dimers and non-specific products.

Conclusions

The one-step SYBR Green I RT-PCR is specific, sensitive and reproducible for the quantification of BVDV in cell culture. This one-step SYBR Green I RT-PCR strategy may be further optimized as a reliable assay for diagnosing and monitoring BVDV infection in animals. It may also be applied to evaluate candidate agents against HCV using BVDV cell culture model.

Occurrence of Chlamydiaceae, Mycoplasma conjunctivae, and pestiviruses in Alpine chamois (Rupicapra r. rupicapra) of Grisons, Switzerland

Because interactions between livestock and chamois occur on Alpine pastures, transmission of infectious diseases is considered possible. Thus, the occurrence of Chlamydiaceae, Mycoplasma conjunctivae, and pestiviruses in Alpine chamois (Rupicapra r. rupicapra) of the Surselva region (eastern Swiss Alps) was investigated. In total, 71 sera, 158 eye swabs, 135 tissue samples, and 23 fecal samples from 85 chamois were analyzed. The sera were tested by 2 enzyme-linked immunosorbent assay (ELISA) kits specific for Chlamydophila abortus. Eye swabs, tissue, and fecal samples were examined by a Chlamydiaceae-specific real-time polymerase chain reaction (PCR). Positive cases were further investigated by microarray method. One serum sample (1.4%) was positive in 1 of the ELISAs. Eye swabs of 3 chamois (3.8%) were positive for Chlamydiaceae. The microarray method revealed the presence of Chlamydophila abortus, C. pecorum, and C. pneumoniae. All tissue and fecal samples were negative. With real-time PCR, 3.9% of the chamois tested positive for Mycoplasma conjunctivae. One chamois had a simultaneous infection with M. conjunctivae and 2 chlamydial species (C. abortus, C. pecorum). Skin and tongue tissue samples of 35 chamois were negative for pestivirus antigen by immunohistochemistry. It was concluded that in contrast to the findings in Pyrenean chamois (Capra p. pyrenaica) of Spain, the occurrence of Chlamydiaceae in Alpine chamois of the Surselva region is low, and the transmission between domestic and wild Caprinae seems not to be frequent. Comparably, persistent pestiviral infections do not seem to be common in chamois of the Surselva region.

Antibody responses against non-structural protein 3 of bovine viral diarrhoea virus in milk and serum samples from animals immunised with an inactivated vaccine

Antibodies against non-structural protein 3 (NS3, p80) of bovine viral diarrhoea virus (BVDV) were determined in milk from cows vaccinated with an inactivated BVDV vaccine and compared to serum antibody levels. Animals in one herd were vaccinated with an inactivated BVDV vaccine according to the standard protocol and animals from a second herd with an intensive schedule. Serum and milk samples were tested for BVDV NS3 antibodies using five commercial ELISAs. With a few exceptions, vaccination according to the standard schedule did not induce BVDV NS3-specific antibodies in serum or milk. However, after vaccination according to the intensive schedule, anti-NS3 antibodies were detected for a short time in serum and, to a lesser extent, in milk. Bulk milk was a suitable substrate for BVDV monitoring of herds vaccinated with the inactivated BVD vaccine.

A Simulation Model to Quantify the Value of Implementing Whole-Herd Bovine Viral Diarrhea Virus Testing Strategies in Beef Cow–Calf Herds

Although numerous diagnostic tests are available to identify cattle persistently infected (PI) with Bovine viral diarrhea virus (BVDV) in cow–calf herds, data are sparse when evaluating the economic viability of individual tests or diagnostic strategies. Multiple factors influence BVDV testing in determining if testing should be performed and which strategy to use. A stochastic model was constructed to estimate the value of implementing various whole-herd BVDV cow–calf testing protocols. Three common BVDV tests (immunohistochemistry, antigen-capture enzyme-linked immunosorbent assay, and polymerase chain reaction) performed on skin tissue were evaluated as single- or two-test strategies. The estimated testing value was calculated for each strategy at 3 herd sizes that reflect typical farm sizes in the United States (50, 100, and 500 cows) and 3 probabilities of BVDV-positive herd status (0.077, 0.19, 0.47) based upon the literature. The economic value of testing was the difference in estimated gross revenue between simulated cow–calf herds that either did or did not apply the specific testing strategy. Beneficial economic outcomes were more frequently observed when the probability of a herd being BVDV positive was 0.47. Although the relative value ranking of many testing strategies varied by each scenario, the two-test strategy composed of immunohistochemistry had the highest estimated value in all but one herd size–herd prevalence permutation. These data indicate that the estimated value of applying BVDV whole-herd testing strategies is influenced by the selected strategy, herd size, and the probability of herd BVDV-positive status; therefore, these factors should be considered when designing optimum testing strategies for cow–calf herds.