Use of pooled serum samples to assess herd disease status using commercially available ELISAs.

Pooled samples are used in veterinary and human medicine as a cost-effective approach to monitor disease prevalence. Nonetheless, there is limited information on the effect of pooling on test performance, and research is required to determine the appropriate number of samples which can be pooled. Therefore, this study aimed to evaluate the use of pooled serum samples as a herd-level surveillance tool for infectious production-limiting diseases: bovine viral diarrhoea (BVD), infectious bovine rhinotracheitis (IBR), enzootic bovine leukosis (EBL) and Neospora caninum (NC), by investigating the maximum number of samples one can pool to identify one positive animal, using commercial antibody-detection ELISAs. Four positive field standards (PFS), one for each disease, were prepared by pooling highly positive herd-level samples diagnosed using commercially available ELISA tests. These PFS were used to simulate 18 pooled samples ranging from undiluted PFS to a dilution representing 1 positive in 1,000 animals using phosphate-buffered saline as diluent. A 1:10 dilution of the PFS resulted in positive results for IBR, BVD and EBL. Moreover, for IBR and BVD, results were still positive at 1:100 and 1:30 dilutions, respectively. However, for NC, a lower dilution (8:10) was required for a seropositive result. This study indicates that, at herd-level, the use of pooled serum is a useful strategy for monitoring infectious diseases (BVD, IBR and EBL) but not NC, using readily available diagnostic assays.

Epidemiology of age-dependent prevalence of Bovine Herpes Virus Type 1 (BoHV-1) in dairy herds with and without vaccination.

Many studies report age as a risk factor for BoHV-1 infection or seropositivity. However, it is unclear whether this pattern reflects true epidemiological causation or is a consequence of study design and other issues. Here, we seek to understand the age-related dynamics of BoHV-1 seroprevalence in seasonal calving Irish dairy herds and provide decision support for the design and implementation of effective BoHV-1 testing strategies. We analysed seroprevalence data from dairy herds taken during two Irish seroprevalence surveys conducted between 2010 and 2017. Age-dependent seroprevalence profiles were constructed for herds that were seropositive and unvaccinated. Some of these profiles revealed a sudden increase in seroprevalence between adjacent age-cohorts, from absent or low to close to 100% of seropositive animals. By coupling the outcome of our data analysis with simulation output of an individual-based model at the herd scale, we have shown that these sudden increases are related to extensive virus circulation within a herd for a limited time, which may then subsequently remain latent over the following years. BoHV-1 outbreaks in dairy cattle herds affect animals independent of age and lead to almost 100% seroconversion in all age groups, or at least in all animals within a single epidemiological unit. In the absence of circulating infection, there is a year-on-year increase in the age-cohort at which seroprevalence changes from low to high. The findings of this study inform recommendations regarding testing regimes in the context of contingency planning or an eradication programme in seasonal calving dairy herds.

Seroprevalence and risk factors assessment of the three main infectious agents associated with abortion in dairy cattle in Isfahan province, Iran.

This study aimed to determine the seroprevalence and identify the risk factors associated with Neospora caninum, Bovine herpesvirus type 1 (BHV-1), and Bovine viral diarrhea virus (BVDV) infection on industrial Holstein dairy cattle farms in Isfahan province, Central Iran. Blood samples were taken from 216 apparently healthy cattle from 16 randomly selected Holstein dairy farms in the North, South, East, and West of Isfahan in the summer of 2017. The antibodies to N. caninum, BHV-1, and BVDV were detected using a commercially available ELISA kit. The overall seroprevalence for N. caninum, BHV-1, and BVDV was 19%, 72.2%, and 52.8%, respectively. The significant major risk factors of BHV-1 in cattle were identified as farm direction, age groups, parity, and milk yield by the univariate analysis (p < 0.05). The significant major risk factors of BVDV in cattle were identified as age groups, parity, milk yield, and stage of pregnancy (p < 0.05). The only significant major risk factor of N. caninum was farm direction (p < 0.05). A significant association of concurrent infection with BVDV and BHV-1 has shown in the current study (p < 0.05). This study is the first to report the risk factors for N. caninum, BHV-1, and BVDV infection in the central part of Iran and allows us to conclude that these agents are widely distributed in this region.

The role of goats as reservoir hosts for bovine herpes virus 1 under field conditions.

Bovine herpesvirus 1 (BoHV1) is the cause of economically significant viral infections in cattle. Respiratory symptoms associated with the infection are known as Infectious Bovine Rhinotracheitis (IBR). Sheep and goats are less sensitive to the infection although their role in inter-species viral transmission under field conditions is subject to controversy. The objective of this study was to investigate seroprevalence of BoHV1 infections in cattle, sheep, and goats raised together for at least a year. Blood serum samples were taken from 226 cattle, 1.053 sheep, and 277 goats from 17 small- to medium-scale farms. BoHV1-specific antibody presence and titers were determined using virus neutralization test. In total, 73 of the 226 cattle (32.3%) were seropositive. The infection was detected in 13 of the 17 farms. Infection rates ranged from 5.8 to 88.8%. Only one of the 1053 sheep (0.09%) was seropositive. However, 58 of the 277 (20.9%) goats were seropositive. Goat samples taken from 8 of the 17 farms were seropositive with infection rates ranging from 17 to 38.9%. Statistical analysis showed a significant correlation in infection rates between cattle and goats but not sheep. These results suggest that goats may be more sensitive to the BHV1 infection than sheep and the role of goats as possible reservoirs for BoHV1 in the control and eradication of BHV1 in cattle should be considered in future studies.

Bovine herpesvirus 1: within-herd seroprevalence and antibody levels in bulk-tank milk.

The aim of the present study was to establish a relationship between the results obtained with the enzyme-linked immunosorbent assay (ELISA) technique for antibodies (against bovine herpesvirus 1) in serum and those in milk at the herd level. For this purpose, 275 samples of bulk-tank milk were analysed with glycoprotein E (gE) antibody ELISA and 207 more were analysed with glycoprotein B (gB) antibody ELISA (482 in total). All of these samples came from dairy herds whose seroprevalence was also evaluated. The results of this study were then used to analyse the sensitivity of the bulk-tankmilk test in detecting herds with a high risk of active infection (>60% seroprevalence) and its specificity in detecting those with few (<20%) or no seropositive animals. In regard to the reference test (results in blood serum), the sensitivity of the bulk-tankmilk test in detecting herds with >60% seropositive animals was 100% for both gE and gB ELISAs. The specificity figures, for gE and gB ELISAs, respectively, were 88.4% and 99.1% for infection-free herds and 72.6% and 96% for herds with <20% seroprevalence. In a quantitative approach, Pearson's correlation coefficients, reported as a measure of linear association between herd seroprevalences and transformed optical density values recorded in bulk-tank milk, were -0.63 for gE ELISA and 0.67 for gB ELISA.

Les auteurs présentent une étude visant à faire ressortir la corrélation entre les résultats obtenus à l'échelle du troupeau au moyen d'une épreuve immunoenzymatique (ELISA) pour la détection d'anticorps dirigés contre l'herpèsvirus bovin de type 1 dans des échantillons de sérum et ceux obtenus dans le lait. À cet effet, 275 échantillons de lait de citerne ont été soumis à un test ELISA visant à déceler la présence d'anticorps dirigés contre la glycoprotéine E (gE) du virus, et 207 autres ont été analysés au moyen d'un test ELISA visant à déceler la présence d'anticorps dirigés contre la glycoprotéine B (gB) (482 échantillons analysés au total). La totalité des échantillons provenait d'élevages laitiers dans lesquels la séroprévalence a également été evaluée. Les résultats de l'étude ont ensuite permis d'analyser la sensibilité du test sur le lait de citerne, c'est-àdire la capacité de ce test à détecter les troupeaux présentant un risque élevé d'infection active (séroprévalence > 60 %), ainsi que sa spécificité, c'est-à-dire sa capacité à détecter les troupeaux dans lesquels le pourcentage d'animaux séropositifs était faible (moins de 20 %) ou nul (0 %). Comparativement au test de référence (analyse des échantillons de sérum), la sensibilité des tests ELISA sur le lait de citerne était de 100 % (détection de tous les troupeaux dotés d'au moins 60 % d'animaux possédant des anticorps dirigés contre la glycoprotéine E ou B). En termes de spécificité des tests ELISA anti-gE et anti-gB, les valeurs étaient, respectivement, de 88,4 % et 99,1 % dans les troupeaux indemnes et de 72,6 % et 96 % dans les troupeaux accusant une séroprévalence inférieure à 20 %. Les coefficients de corrélation de Pearson obtenus par une méthode quantitative pour exprimer la relation linéaire entre les prévalences sérologiques et les valeurs de densité optique modifiées dans le lait de citerne étaient respectivement de ­0,63 pour l'ELISA gE et de 0,67 pour l'ELISA gB.

Los autores describen un estudio encaminado a determinar si existe una relación, y de ser así cuál, entre los resultados del ensayo inmunoenzimático (ELISA) de detección de anticuerpos (contra el herpesvirus bovino 1) en suero y los resultados obtenidos al analizar la leche de rebaños enteros. Para ello se sometieron 275 muestras de leche de tanque a la prueba ELISA de detección de anticuerpos contra la glicoproteína E (gE) y otras 207 muestras a la prueba ELISA de detección de anticuerpos contra la glicoproteína B (gB) (esto es, un total de 482 muestras). Todas esas muestras procedían de rebaños lecheros cuya prevalencia serológica también se calculó. A partir de los resultados del estudio se determinó la sensibilidad de la prueba practicada en la leche de tanque para detectar rebaños con un elevado riesgo de infección activa (más del 60% de animales seropositivos) y su especificidad para detectar aquellos rebaños con pocos (menos del 20%) animales seropositivos o ninguno (0%). En comparación con la prueba de referencia (resultados del análisis sérico), la sensibilidad del análisis de la leche de tanque para detectar rebaños con más de un 60% de animales seropositivos fue del 100% en el caso de ambas pruebas ELISA (gE y gB). En cuanto a la especificidad, las técnicas ELISA para la gE y la gB permitieron detectar respectivamente un 88,4% y un 99,1% de los rebaños libres de infección y un 72,6% y un 96% de los rebaños con menos de un 20% de animales seropositivos. El análisis cuantitativo de los resultados deparó coeficientes de correlación de Pearson, utilizados como medida de la relación lineal entre las seroprevalencias de rebaño y los valores transformados de densidad óptica obtenidos en la leche de tanque, de ­0,63 para el ELISA gE y de 0,67 para el ELISA gB.

Pathogens at the livestock-wildlife interface in Western Alberta: does transmission route matter?

In southwestern Alberta, interactions between beef cattle and free-ranging elk (Cervus elaphus) may provide opportunities for pathogen transmission. To assess the importance of the transmission route on the potential for interspecies transmission, we conducted a cross-sectional study on four endemic livestock pathogens with three different transmission routes: Bovine Viral Diarrhea Virus and Bovine Herpesvirus 1 (predominantly direct transmission), Mycobacterium avium subsp. paratuberculosis (MAP) (indirect fecal-oral transmission), Neospora caninum (indirect transmission with definitive host). We assessed the occurrence of these pathogens in 28 cow-calf operations exposed or non-exposed to elk, and in 10 elk herds exposed or not to cattle. We characterized the effect of species commingling as a risk factor of pathogen exposure and documented the perceived risk of pathogen transmission at this wildlife-livestock interface in the rural community. Herpesviruses found in elk were elk-specific gamma-herpesviruses unrelated to cattle viruses. Pestivirus exposure in elk could not be ascertained to be of livestock origin. Evidence of MAP circulation was found in both elk and cattle, but there was no statistical effect of the species commingling. Finally, N. caninum was more frequently detected in elk exposed to cattle and this association was still significant after adjustment for herd and sampling year clustering, and individual elk age and sex. Only indirectly transmitted pathogens co-occurred in cattle and elk, indicating the potential importance of the transmission route in assessing the risk of pathogen transmission in multi-species grazing systems.

Seroprevalence and Associated Risk Factors of Infectious Bovine Rhinotracheitis (IBR) and Animal Owners' Knowledge, Attitude and Practice (KAP) Towards the Disease in Selected Districts of East Wollega Zone, Oromia Regional State, Ethiopia.

PURPOSE: Infectious bovine rhinotracheitis (IBR) is one of the most important diseases affecting production and productivity. METHODOLOGY: Cross-sectional study was aimed at to determine the seroprevalence of IBR and associated risk factors, and animal owners' knowledge, attitude and practice towards the disease from April 2021 to June 2022. Accordingly, a total of 384 serum samples were collected from both crossbreed (70) and local breed (314) cattle from purposively selected districts of East Wollega zone of Western Ethiopia. Competitive enzyme-linked immunosorbent assay (ELISA) was used for testing glycoprotein antibodies (anti-gB) for bovine herpes virus-1 (BoHV-1) virus in collected serum, and the obtained data were analysed by multiple logistic regressions by using R software 3.62 version. However, questionnaire data were analysed for descriptive statistics by SPSS version 20.0 (IBM. Corp, 2011). RESULT: The total prevalence of IBR in the study area was found to be 70.54% at herd and 80.47% at individual cattle level. The significant association (p  < 0.05 $ < \ 0.05$ ) was found for breed, age, body condition and herd size but not for district and sex as risk factors. The BoHV-1 virus seropositivity in adult animals increased significantly, with an odds ratio of 1.65 (95% CI 0.705-3.85) compared to young. Local breed cattle were 2.055 times more likely to test positive for IBR with an odds ratio of 0.77 (95% CI 0.23-2.22) compared to crossbreed cattle. The chances of cattle in medium herds testing positive for the BoHV-1 virus with an odds ratio of (1.78 95% CI 1.303-7.50) are greater than the chances of cattle in smaller herds testing positive. The survey results showed that 70% of animal owners identified IBR as a major challenge in animal production, whereas 35% mentioned long calving intervals. However, 92% of the participants were not informed about the level of knowledge and attitude regarding particular diseases such as IBR. CONCLUSION: This study showed that there is a high prevalence of IBR in cattle in the study area, and that owners have low awareness of the disease. Therefore, it is necessary to develop an immediate control system and conduct additional research on molecular detection to evaluate its effects on reproductive performance.

The seasonality as a relevant aspect to be considered for differential diagnosis of Trypanosoma vivax infection and co-infections in female cattle.

Bovine Trypanosomiasis and other infectious diseases cause relevant loss for the livestock industry impacting productive/reproductive indices. This study intended to better understand the frequency, seasonality, and profile of infections associated with Bovine Trypanosomiasis. A total of 1443 serum samples were screened for T. vivax infection and other infectious diseases: Neosporosis, Leptospirosis, Bovine Leukosis Virus infection/(BLV), Infectious Bovine Rhinotracheitis/(IBR) or Bovine Viral Diarrhea/(BVD). Distinct methods were used for screening and diagnosis: immunofluorescence assay (Trypanosomiasis), ELISA (Neosporosis,BLV,IBR,BVD) and microscopic agglutination test (Leptospirosis). Our findings demonstrated that the seropositivity for Trypanosomiasis=57% was similar to Neosporosis=55%, higher than Leptospirosis=39% and BVL=34%, but lower than IBR=88% and BVD=71%. The seropositivity for Trypanosomiasis was higher in the autumn and lower in the winter. Regardless the season, the IBR seropositivity (min=73%;max=95%) was higher than Trypanosomiasis (min=48%;max=68%). Moreover, Neosporosis (min=71%;max=100%) and BVD (min=65%;max=76%) were more frequent than Trypanosomiasis in the summer, winter and spring. The diagnosis outcome revealed that Trypanosomiasis&IBR=43% and Trypanosomiasis&Neosporosis=35% were the most frequent co-infections with higher seropositivity in the autumn (58%) and summer (80%), respectively. Noteworthy, high seropositivity to Trypanosomiasis&BVD was registered in the autumn (46%). Together, our data re-enforce the relevance of differential diagnosis between Trypanosomiasis with other bovine infectious diseases and that differences in the seasonality profile is a relevant aspect to be considered while selecting the differential diagnosis to be applied.

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

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

Presence of co-infection between bovine leukemia virus and bovine herpesvirus 1 in herds vaccinated against bovine respiratory complex.

The aim of this study was molecular identification of bovine leukemia virus and possible co-infection with bovine respiratory disease complex (BRDC) viral agents in Mexican dairy herds. We collected 533 blood samples from cattle vaccinated against the BRDC virus in 9 states across Mexico. Peripheral blood leukocytes were removed and genetic material was extracted to detect bovine leukemia virus (BLV), bovine herpesvirus 1 (BoHV-1), bovine viral diarrhea virus (BVDV), bovine parainfluenza virus 3 (BPIV-3), and bovine respiratory syncytial virus (BRSV) infection using polymerase chain reaction. We identified high BLV infection rates in 270 cattle (50.65%). One hundred and thirty-three cows (24.95%) tested positive for BoHV-1, of which 65 samples were positive for both viruses (BoHV-1 and BLV) and 68 were only positive for BoHV-1. Only 4 samples tested positive for BPIV-3 and no sample was positive for BVDV or BRSV. Relative risk and odds ratio analyses did not identify that the presence of BLV infection favors BoHV-1 co-infection in vaccinated herds.

Le but de cette étude était l'identification moléculaire du virus de la leucémie bovine et une éventuelle co-infection par des agents viraux du complexe des maladies respiratoires bovines (BRDC) dans des troupeaux laitiers mexicains. Nous avons recueilli 533 échantillons de sang de bovins vaccinés contre le virus BRDC dans neuf états du Mexique. Les leucocytes du sang périphérique ont été prélevés et le matériel génétique a été extrait pour détecter le virus de la leucémie bovine (BLV), le virus de l'herpès bovin 1 (BoHV-1), le virus de la diarrhée virale bovine (BVDV), le virus parainfluenza bovin 3 (BPIV-3), et le virus respiratoire syncytial bovin (BRSV) par réaction d'amplification en chaîne par la polymérase. Nous avons identifié des taux élevés d'infection par le BLV chez 270 bovins (50,65 %). Cent trente-trois bovins (24,95 %) ont été testés positifs pour le BoHV-1, desquels 65 échantillons étaient positifs pour les deux virus (BoHV-1 et BLV) et 68 étaient uniquement positifs pour le BoHV-1. Seuls quatre échantillons ont été testés positifs pour le BPIV-3 et aucun échantillon n'a été positif pour le BVDV ou le BRSV. Les analyses du risque relatif et des rapports de cotes n'ont pas identifié que la présence d'une infection par le BLV favorise la co-infection par le BoHV-1 dans les troupeaux vaccinés.(Traduit par les auteurs).

Seroprevalence of BHV-1 (bovine herpesvirus type 1) among non-vaccinated dairy cattle herds with respiratory disorders.

The objective of this study was to estimate a herd-level seroprevalence of bovine herpesvirus type 1 (BHV-1) in herds with clinical symptoms of the respiratory tract. Eighty-three herds with suspected BHV-1 infection were selected and divided into two categories with respect to their size: small (n = 27) and large herds (n = 56). Samples were collected from calves, heifers and cows older than 24 months. Seroprevalence was determined using the gB ELISA test. The herd level seroprevalence was estimated as 53% (44/83) in the tested herds, 11.1% (3/27) in the small herds and 73.2% (41/56) in the large herds. Our study suggests that the current biosecurity measures still warrant improvement.

Using scenario tree modelling for targeted herd sampling to substantiate freedom from disease.

BACKGROUND: In order to optimise the cost-effectiveness of active surveillance to substantiate freedom from disease, a new approach using targeted sampling of farms was developed and applied on the example of infectious bovine rhinotracheitis (IBR) and enzootic bovine leucosis (EBL) in Switzerland. Relevant risk factors (RF) for the introduction of IBR and EBL into Swiss cattle farms were identified and their relative risks defined based on literature review and expert opinions. A quantitative model based on the scenario tree method was subsequently used to calculate the required sample size of a targeted sampling approach (TS) for a given sensitivity. We compared the sample size with that of a stratified random sample (sRS) with regard to efficiency. RESULTS: The required sample sizes to substantiate disease freedom were 1,241 farms for IBR and 1,750 farms for EBL to detect 0.2% herd prevalence with 99% sensitivity. Using conventional sRS, the required sample sizes were 2,259 farms for IBR and 2,243 for EBL. Considering the additional administrative expenses required for the planning of TS, the risk-based approach was still more cost-effective than a sRS (40% reduction on the full survey costs for IBR and 8% for EBL) due to the considerable reduction in sample size. CONCLUSIONS: As the model depends on RF selected through literature review and was parameterised with values estimated by experts, it is subject to some degree of uncertainty. Nevertheless, this approach provides the veterinary authorities with a promising tool for future cost-effective sampling designs.

Seroprevalence of infectious bovine rhinotracheitis and bovine viral diarrhea virus type 1 and type 2 in non-vaccinated cattle herds in the Pacific Region of Central Costa Rica.

The objectives of this cross-sectional study were to estimate the seroprevalence of infectious bovine rhinotracheitis (IBR, BHV-1) and bovine viral diarrhea virus (BVDV) in a population of non-vaccinated, double purpose, dairy and beef herds in the Pacific Region of Central Costa Rica. Blood samples were collected from a total of 496 animals from 35 herds. Sera were tested for antibodies against BHV-1(IBR) and BVDV types 1 and 2 using serum neutralization test. The average number of animals tested in each herd for each of the viruses was 14. Overall individual seroprevalence was 48%, 27%, and 19% for IBR, BVDV type 1, and BVDV type 2, respectively. Median within-herd seroprevalence for IBR, BVDV type 1 and type 2 were 43%, 27%, and 24%, respectively.

A large-scale epidemiological model of BoHV-1 spread in the Irish cattle population to support decision-making in conformity with the European Animal Health Law.

We present a new modelling framework to address the evaluation of national control/surveillance programs planned in line with the European Animal Health Law (AHL) for livestock diseases. Our modelling framework is applied to the cattle sector in Ireland where there is need for policy support to design an optimal programme to achieve bovine herpesvirus type 1 (BoHV-1) free status under the AHL. In this contribution, we show how our framework establishes a regional model that is able to mechanistically reproduce the demography, management practices and transport patterns of an entire cattle population without being dependent on continuous livestock registry data. An innovative feature of our model is the inclusion of herd typing, thereby extending these beyond the categories of dairy, beef and mixed herds that are frequently considered in other regional modelling studies. This detailed representation of herd type-specific management facilitates comparative assessment of BoHV-1 eradication strategies targeting different production types with individual strategy protocols. Finally, we apply our model to support current discussions regarding the structure and implementation of a potential national BoHV-1 eradication programme in Ireland.

Control programs for infectious bovine rhinotracheitis (IBR) in European countries: an overview.

Infectious bovine rhinotracheitis (IBR), caused by Bovine alphaherpesvirus 1 (BoHV-1), is a disease of cattle responsible for significant economic losses worldwide. IBR is under certain communitarian regulations. Every member state can approve its own national IBR control program for the entire territory - or part of it - and can demand additional guarantees for bovids destined to its territory; therefore, every member state can be officially declared as entirely or partly IBR-free. The aim of this review is to provide an overview of IBR control and eradication programs in European countries. BoHV-1 control schemes were first introduced in the late 1970s, mainly in Northern and Central Europe. Depending on the seroprevalence rate, control strategies rely on identification and removal of seropositive animals or the use of glycoprotein E (gE)-deleted marker vaccines in infected herds. The implementation of a novel law for disease eradication at the EU level and of a European IBR data flow could make the goal of IBR eradication in all European countries easier to achieve.

[Infectious bovine rhinotracheitis (IBR) in the canton of Jura: an epidemiological outbreak investigation]. / Rhino-trachéite infectieuse bovine (IBR) dans le canton du Jura: enquête épidémiologique.

Following an abortion in a beef herd in the summer of 2009, three outbreaks of infectious bovine rhinotracheitis (IBR) were diagnosed in the cantons of Jura and Neuchatel. An epidemiological outbreak investigation was conducted with the aims to identify the source of introduction of the bovine herpes virus 1 (BoHV-1) into the affected herds and to prevent further spread of the disease. The attack rates in the three outbreak farms were 0.89, 0.28 and 0, respectively. BoHV-1 could be isolated from nasal swabs of two animals originating from one of the affected farms. Comparative restriction enzyme analysis revealed slight differences between the isolates of the two animals, but a high similarity to previous BoHV-1 isolates from the canton of Jura, as well as to a French BoHV-1 isolate. This IBR outbreak has shown the importance of reporting and analyzing abortions. The current disease outbreaks recall the main risk factors for the spread of IBR in Switzerland: purchase and movement of bovines and semen of often unknown IBR status.

Serological evidence of bovine herpesvirus-1 (BoHV-1) infection in yaks (Peophagus grunniens) from the National Research Centre on Yak, India.

Bovine herpesvirus-1 (BoHV-1) causes a variety of disease syndromes including, respiratory, nervous and reproductive disorders both in domestic as well as wild bovines and the disease is prevalent throughout the world including India. In this study, serum samples of yaks were screened for serological evidence of BoHV-1 in a yak farm with history of abortion and kerato-conjuctivitis by competition-ELISA. The result of seroprevalence of BoHV-1 infections in yaks (Poephagus grunniens) revealed that the overall seroprevalence was 60.1%. The sero-prevalence of BoHV-1 infections was highest in male calf (67.7%) followed by yak cows (62.6%), yak bulls (56.8%), and yak heifers (50.0%).

Prevalence of brucellosis and infectious bovine rhinotracheitis in organized dairy farms in India.

This study was carried out to investigate the prevalence of bovine brucellosis and infectious bovine rhinotracheitis (IBR) in organized dairy farms with history of abortion in India. ELISA and Rose Bengal Plate Test (RBPT) were used to detect the seropositive animals and the test results indicated that 22.18% and 13.78% animals were declared as sero-positive by ELISA and RBPT, respectively. Milk Ring Test (MRT) was carried out only in one farm and 12.82% of the tested animals were turned positive. Culture examination analysis of milk samples, two animals revealed the presence of organisms indistinguishable from Brucella spp. The organism was confirmed as brucella by morphological characteristics and biochemical tests. An overall sero-prevalence of antibodies against IBR was found to be 60.84%. None of the genital and nasal swab samples was found to be positive for presence of bovine herpesvirus -1 (BHV-1) on repeated passage in Madin-Darby Bovine Kidney (MDBK) cell lines. Brucella and IBR considered as the causal agent for abortions in these farms. The present study indicates the urgent need and the necessity for control of these infectious diseases which cause heavy economic losses to the organized farms.

Seroconversion to bovine viral diarrhoea virus and infectious bovine rhinotracheitis virus in dairy herds of Michoacan, Mexico.

Bovine viral diarrhoea virus (BVDV) and infectious bovine rhinotracheitis virus (IBRV) are important viral diseases around the world. The objective of this study was to estimate the incidence of seroconversion to BVDV and IBRV and to identify associated risk factors in dairy herds of Michoacan, Mexico. The longitudinal study included 62 herds and ran from December 2001 to November 2002. The total number of animals enrolled and completing the study were 392 and 342 animals for BVDV and 925 and 899 animals for IBRV. Animals were tested monthly for 12 months, for the presence of antibodies. Risk factors were: herd size (2-9, 10-25 and 26-55 animals), herd serostatus (seropositive or seronegative, only for IBRV), age group of the animal (6 to 12, 13 to 24, 25 to 48 and > 48 months) and animal origin (born in farm, purchased). The cumulative incidences for BVDV and IBRV were 16.4% and 3.4%, respectively; whereas, the incidence density rates for BVDV and IBRV were 15.9 and 2.9 per 1000 animal-months at risk, respectively. Seroconversion curves were statistically different for age group for BVDV and IBRV and for herd status for IBR. The relatively high incidence of seroconversion for BVDV suggests that a successful control programme should be oriented towards the identification and elimination of the PI animals and towards avoiding the introduction of PI cattle to the farm. The scenario of IBRV is favourable to implement a programme directed to reduce the number of new seropositive herds.

Sero-prevalence and risk factors of infectious bovine rhinotracheitis virus (type 1) in Meru County, Kenya.

The aim of the study was to determine the antibody sero-prevalence of Bovine Herpesvirus-1 which cause Infectious Bovine Rhinotracheitis (IBR) and to identify risk factors associated with BHV-1 antibody seropositivity among smallholder dairy farms in Meru County, Kenya. A cross-sectional study was conducted in the Naari area of Meru County, Kenya between September-October 2016 and March-April 2017. The 149 farmers were randomly selected from members of the Naari Dairy Farmers Cooperative Society who were actively delivering milk to the society at the time of the study. Serum samples were obtained from 403 female dairy cattle. Farm level management and animal factors were collected through direct interviews with the owner or someone who was knowledgeable about the animals. All serum samples were processed with an indirect enzyme-linked immunosorbent assay (gB ELISA) to determine the presence of antibodies to BHV-1. The overall farm-level and animal-level sero-prevalences of BHV-1 antibodies were 30.9 % (95 % CI: 23.6%-39.0%) and 17.4 % (95 % CI: 13.8%-21.4%), respectively. In the final multivariable analysis, the factors significantly associated with BHV-1 antibodies included; age of the dairy cattle (OR = 1.200, p = 0.001), age of the principal female farmers (OR = 0.182, p = 0.001) and rearing goats in the farm (OR = 26.77, p = 0.000). There was a significant interaction between rearing goats on the farm and age of the dairy cattle (p < 0.010); younger cattle seemed to have been exposed to BHV or a cross-reacting caprine herpesvirus when goats were on the farm. The results showed that BHV-1 was circulating among the cattle population in the Naari area of Meru County. Given that there is not BHV-1 vaccination use in this study population, training on the importance of biosecurity and vaccination for BHV-1 are recommended to reduce the transmission and impacts of BHV-1.