Prevalence of bovine herpesvirus-1 in the Belgian cattle population

The national bovine herpesvirus 1 (BHV-1) seroprevalence (apparent prevalence) in the Belgian cattle population was determined by a serological survey that was conducted from December 1997 to March 1998. In a random sample of herds (N=556), all cattle (N=28 478) were tested for the presence of antibodies to glycoprotein B of BHV-1. No differentiation could be made between vaccinated and infected animals, because the exclusive use of marker vaccines was imposed by law only in 1997 by the Belgian Veterinary Authorities. Twenty-one percent of the farmers vaccinated continuously against BHV-1.

In the unvaccinated group, the overall herd, individual-animal and median within-herd seroprevalences were estimated to be 67% (95% confidence interval (CI)=62–72), 35.9% (95% CI=35.0–36.8) and 33% (quartiles=14–62), respectively.

Assuming a test sensitivity and specificity of 99 and 99.7%, respectively, the true herd, individual-animal and median within-herd prevalence for the unvaccinated group of herds were estimated to be 65, 36 and 34%, respectively. The true herd prevalence for dairy, mixed and beef herds were respectively, 84, 89 and 53%; the true individual-animal prevalence for those types of herds were, respectively, 35, 43 and 31%; whereas, the true median within-herd prevalences were 36, 29 and 38%.     

Neospora caninum seroprevalence in dairy and beef cattle from the northwest region of Spain, Galicia

Herd and individual animal seroprevalence for Neospora caninum (N. caninum) in dairy, beef and mixed cattle were obtained in all populations within the Galician Farmer Sanitary Defence Associations (ADSG) in 2004. All animals ≥1 year of age were examined serologically by indirect ELISA. 1147 dairy herds (37,090 animals), 1464 beef herds (20,206 animals) and 141 mixed herds (2292 animals) were surveyed. True herd seroprevalence was estimated to be 80.6% (87.7% dairy, 76.7% beef and 78.4% mixed herds), true animal seroprevalence was estimated to be 23.2% (21.9% dairy, 25.1% beef and 24.9% animal to mixed herds), and within-herd seroprevalence was estimated to be 25.4% (23.6% dairy, 28.3% beef and 28.6% to mixed herds). Seropositivity was significantly associated with herd type (higher in dairies), herd size (increased when herd size increases), animal type (higher in beef) and age (lineal increase with the age). Results obtained in this study will be used for the development of a N. caninum control programme in the ADSG in Galicia.     

Supranational comparison of Neospora caninum seroprevalences in cattle in Germany, The Netherlands, Spain and Sweden

Herd, within-herd and animal prevalences for Neospora caninum in beef and dairy cattle were compared between four countries. In randomly selected herds from regions of Germany, The Netherlands, Spain and Sweden that were representative for the cattle production of these countries, all animals > or = 2 years were examined serologically by enzyme-linked immunosorbent assays (ELISAs) with high test specificity (> 98.0%). In a previous study, the ELISAs had been validated against each other. Single reacting animals within a herd were confirmed by immunobloting. At the time of sampling, animal (age, breed, herdtype, sex, lactation stage) and herd data (region) were collected. Considerable differences in N. caninum herd, within-herd, and overall animal prevalence estimations were observed between countries, regions, herdtype, age categories and breeds. Herd prevalences, based on confirmation of single reactors, for dairy herds were estimated to be 16% (95%CI: 10-24%) in Sweden, 49% (95%CI: 39-59%) in Germany, 63% (95%CI: 57-69%) in Spain and 76% (95%CI: 67-84%) in The Netherlands and for beef herds 41% (95%CI: 31-50%) in Germany, 46% (95%CI: 41-51%) in Spain and 61% (95%CI: 50-72%) in The Netherlands. No beef herds were examined in Sweden. The lowest animal true prevalence was estimated in dairy cattle in Sweden (0.5% (95%CI: 0.1-0.8%)) while the highest animal true prevalence was estimated for dairy cattle in Spain (16.2% (95%CI: 14.9-17.5%)). Within-herd prevalences varied greatly, with very few farms in Sweden having more than 10% seropositive animals while in Spain more than 10% of the herds had within-herd prevalences between 50 and 100%. Seropositivity was significantly associated with herdtype (beef versus dairy), age, breed and region within countries. The results of this supranational comparative study showed that the importance of N. caninum infection varied greatly within in Europe. Estimates of prevalence can be used to calculate the economic impact of N. caninum infection as well as to evaluate the effect of prevention and control strategies over time.     

Prevalence and distribution of paratuberculosis (Johne's disease) in cattle herds in Ireland

A simple random survey was conducted in Ireland during 2005 to estimate the ELISA-prevalence of paratuberculosis, commonly called Johne's disease (JD), in the cattle population. Serum samples were collected from all 20,322 females/breeding bulls over 12 months-of-age in 639 herds. All samples were tested using a commercially available absorbed ELISA. The overall prevalence of infected herds, based on the presence of at least one ELISA-positive animal, was 21.4% (95% CI 18.4%-24.9%). Herd prevalence levels amongst dairy herds (mean 31.5%; 95% CI: 24.6%, 39.3%) was higher than among beef herds (mean 17.9%; 95% CI: 14.6%-21.8%). However, the animal level prevalence was similar. The true prevalence among all animals tested, was calculated to be 2.86% (95%CI: 2.76, 2.97) and for animals >= 2 yrs, it was 3.30% (95%CI: 3.17, 3.43). For animals in beef herds, true prevalence was 3.09% (95%CI: 2.93, 3.24), and for those in dairy herds, 2.74% (95%CI: 2.59, 2.90). The majority of herds had only one ELISA-positive infected animal. Only 6.4% (95% CI 4.7%-8.7%) of all herds had more than one ELISA-positive infected animal; 13.3% (CI 8.7%-19.7%) of dairy herds ranging from two to eight ELISA-positive infected animals; and, 3.9% beef herds (CI 2.4%-6.2%) ranging from two to five ELISA-positive infected animals. The true prevalence of herds infected and shedding Mycobacterium avium subspecies paratuberculosis is estimated to be 9.5% for all herd types; 20.6% for dairy herds; and 7.6% for beef herds. If ELISA positive animals <2-years-of-age are excluded, the true herd prevalene reduces to: 9.3% for all herd types; 19.6% for dairy herds; and 6.3% for beef herds based on a test specificity (Sp) of 99.8% and test sensitivity (Se) (i.e., ability to detect culture-positive, infected animals shedding at any level) of 27.8-28.9%.     

Prevalence and regional distribution of paratuberculosis in dairy herds in The Netherlands

In the Netherlands a survey was conducted to estimate the prevalence of paratuberculosis in dairy herds. In total 15822 cows of at least 3 years of age, belonging to 378 herds were tested using an absorbed ELISA. Of these herds, 55% (n=207) had one or more serologically positive cows. Of the positive non-vaccinated herds, most had one (n=98) or two (n=49) positive cows. The percentage positive cows per herd was 2.5+/-3.2%.The true prevalences on cow and herd levels, based on a test sensitivity that ranged from 0.3 to 0.4 and a specificity that ranged from 0.985 and 0.995, were estimated at 2. 7-6.9% and 31-71%.Seven herds had been vaccinated against paratuberculosis and these herds had a significantly higher percentage of serologically positive cows (23%) than the non-vaccinated herds (2.5%).In conclusion, a small percentage of the dairy cows and a high percentage of the dairy herds in the Netherlands is serologically positive. The percentages true infected cows and herds are difficult to estimate precisely due to uncertainties in test sensitivity and specificity.     

Prevalence of paratuberculosis (Johne's disease) in the Belgian cattle population

The national bovine paratuberculosis (PTB) seroprevalence (apparent prevalence) in the Belgian cattle population was determined by a serological survey that was conducted from December 1997 to March 1998. In a random sample of herds (N=556, 9.5%), all adult cattle of 24 months of age or older (N=13,317, 0.4%) were tested for the presence of antibodies using a commercially available absorbed ELISA test kit. The PTB median within-herd seroprevalence (proportion of detected animals within the seropositive herds) and the PTB individual-animal seroprevalence (proportion of detected animals) were, respectively, 2.9% (quartiles=1.6-5.6) and 0.87% (95% confidence interval (CI)=0.71-1.03). The PTB herd seroprevalence (proportion of detected herds) was 18% (95% CI=14-21).Assuming a test sensitivity and specificity of 45 and 99% [Sweeney et al., 1995. J. Vet. Diagn. Invest. 7 (4), 488; Sockett et al., 1992. J. Clin. Microbiol. 30 (5), 1134], respectively, the median true within-herd prevalence and the true individual-animal were estimated to be 7 and 2%, respectively. The true herd prevalence of Mycobacterium paratuberculosis infection was first estimated according to currently accepted methodology. This calculation revealed that the specificity of the used test has a dramatic effect on the estimation; assuming a test sensitivity of 45% and a true within-herd prevalence of 7%, the true herd prevalence estimation decreased from 36 to 0.8% if the test specificity decreased from 99. 9 to 99%, respectively. This sensitivity analysis showed that the practical limits of the accuracy of the used screening test jeopardize the estimation of the true herd prevalence within reasonable confidence limits, because the within-herd PTB true prevalence was low.For this reason we augmented the herd specificity for herds with larger adult herd size (>5). This was done by increasing the cut-off number of positive cattle required (>/=2) to classify a herd truly positive and including herds with one positive test result if there was historical evidence of PTB (previous diagnosis and/or clinical signs). This approach resulted in an estimated true herd prevalence of M. paratuberculosis infection of 6%. The true herd prevalence for dairy, mixed and beef herds was, respectively, 10, 11 and 3%.     

An estimated prevalence of Johne's disease in a subpopulation of Alabama beef cattle.

The objective of this study was to estimate the overall prevalence of animals that were infected with Mycobacterium avium ssp. paratuberculosis in a subpopulation of Alabama beef cattle. This was determined using a commercial enzyme-linked immunosorbent assay (ELISA) for the detection of M. avium ssp. paratuberculosis-specific antibodies in serum. Serum was collected from 79 herds that were participating in the Alabama Brucellosis Certification program. A total of 2,073 beef cattle were randomly tested by selecting 30 animals per herd in herds greater than 30 and selecting all animals in herds 30 and less for testing. It has been estimated that the commercial ELISA test used has a 60% sensitivity and a 97% specificity. Of the 79 herds tested, 29 herds were seronegative, 24 herds had 1-2 positive animals, and 26 herds had 3 or more seropositive animals. The average number of infected animals per positive herd was 3.3. In addition, a calculated minimum of 53.5% of the herds were identified as Johne's positive herds with a 95% confidence level. Of the total number of animals tested, 8.0% (166/2,073) of them were positive by the ELISA. After adjustments for test sensitivity and specificity and the proportion of animals sampled per herd, the true prevalence was calculated to be 8.75%. These data suggest that approximately 50% of the herds are infected with M. avium ssp. Paratuberculosis, and the overall prevalence of infection in Alabama beef cattle is approximately 8%, which correlates with other previously published regional estimates.     

Risk factors for bovine herpesvirus-1 seropositivity

This paper reports the investigation of risk factors for bovine herpesvirus-1-seropositivity, based on a cluster-sample survey of the Belgian cattle population. This serosurvey was carried out in 1998 in 309 randomly selected unvaccinated herds of all types (dairy, mixed and beef) were all bovids (N = 11,284) were sampled.

Older and male cattle had higher seroprevalence. Origin (homebred or purchased) and herd size interacted; for smaller herds (≤50 cattle on the premises), purchase status and larger herd size were risk factors, whereas these effects were not observed for larger herds.     

Herd-level seroprevalence and risk-mapping of bovine hypodermosis in Belgian cattle herds

Our objective was to determine the seroprevalence of Hypoderma spp. and to develop a spatial model describing the risk surface of warble-fly infection in Belgian cattle herds (adjusting for herd size, herd type, local temperature, rainfall, relative air humidity and land-cover). This survey was carried out in 390 selected herds of all types (dairy, mixed and beef) from December 1997 to March 1998, which were included in a national infectious bovine rhinotracheitis and paratuberculosis (Johne's-disease) survey. All animals >24 months old were blood sampled and an ELISA was used on pooled serum samples (10 animals per pool). The herd seroprevalence was 48.7% (95% confidence interval: 43.6-53.8); positive herds were mainly in the south of the country and along the North Sea coast. The logistic multiple-regression model of herd-level seropositivity indicated that mixed-type and beef-cattle herds have more than four-fold and two-fold increases in the odds of being Hypoderma-positive, respectively, compared with dairy herds.     

Estimates of within-herd incidence rates of Mycobacterium bovis in Canadian cattle and cervids between 1985 and 1994

We analysed the individual-animal data from six of the nine outbreaks of tuberculosis in Canadian cattle and cervids from 1985 to 1994. A “positive/reactor” animal was one which had either a positive culture or a positive or suspicious reaction on a mid-cervical, comparative cervical, or gross or histopathological test for tuberculosis. Individual-animal data were collected only for herds which had one or more positive/reactor animals. Data were collected from the outbreak records in the Regional or District offices of Agriculture and Agri-food Canada’s Animal and Plant Health Directorate. The within-herd spread of Mycobacterium bovis was studied by determining the most-likely date at which the herd was first exposed to M. bovis and the number of reactions which had developed by the time the herd was investigated. The animal-time units at risk in the herd were probably overestimated, resulting in conservative estimates of the within-herd incidence rates. Negative-binomial regression was used to investigate factors which might have influenced the within-herd spread of tuberculosis. Increasing age appeared to be a risk factor for being a positive/reactor animal. When compared to animals 0–12 months old, animals 13–24 months old had an incidence rate ratio (IRR) of 7.6, while animals >24 months old had an IRR of 10.4 (p=0.009). Actual and predicted incidence rates for tuberculosis in mature (>24 months old) animals were calculated. Actual and predicted incidence rates were similar for cervids, within an outbreak. There was more variability between actual and predicted rates in the dairy and beef animals. In the one outbreak (Ontario) where there were positive/reactor cervid, dairy and beef herds, the actual incidence rate for cervids (IR=9.3 cases per 100 animal-years) was almost twice that of dairy cattle (IR=5.0) and three times that of beef cattle (IR=3.1).     

Seroprevalence of Neospora caninum infection in dairy and beef cattle in Paraguay

Seroprevalence of Neospora caninum in 879 beef and dairy cattle in different locations of Paraguay was determined by an ELISA. In the survey, 262 (29.8%) cattle were positive to N. caninum, and animals with anti-Neospora antibody titre were observed in all the locations tested in the country. Serum samples taken from a herd that exhibited persistent abortion had the highest percentage of animals being positive to the parasite (17/30, 56.7%). In the same herd, abortion was significantly more likely in animals with high anti-Neospora antibody titre. Immunoblot analysis demonstrated that the banding pattern from positive Paraguayan cattle was similar to that seen with the positive control sample. In conclusion, N. caninum infection is present among Paraguayan beef and dairy cattle, and it may be an important cause of bovine abortion in Paraguay.     

Bovine viral diarrhoea virus seroprevalence and vaccination usage in dairy and beef herds in the Republic of Ireland

Background

Bovine viral diarrhoea (BVD) is an infectious disease of cattle with a worldwide distribution. Herd-level prevalence varies among European Union (EU) member states, and prevalence information facilitates decision-making and monitoring of progress in control and eradication programmes. The primary objective of the present study was to address significant knowledge gaps regarding herd BVD seroprevalence (based on pooled sera) and control on Irish farms, including vaccine usage.

Methods

Preliminary validation of an indirect BVD antibody ELISA test (Svanova, Biotech AB, Uppsala, Sweden) using pooled sera was a novel and important aspect of the present study. Serum pools were constructed from serum samples of known seropositivity and pools were analysed using the same test in laboratory replicates. The output from this indirect ELISA was expressed as a percentage positivity (PP) value. Results were used to guide selection of a proposed cut-off (PCO) PP. This indirect ELISA was applied to randomly constructed within-herd serum pools, in a cross-sectional study of a stratified random sample of 1,171 Irish dairy and beef cow herds in 2009, for which vaccination status was determined by telephone survey. The herd-level prevalence of BVD in Ireland (percentage positive herds) was estimated in non-vaccinating herds, where herds were classified positive when herd pool result exceeded PCO PP. Vaccinated herds were excluded because of the potential impact of vaccination on herd classification status. Comparison of herd-level classification was conducted in a subset of 111 non-vaccinating dairy herds using the same ELISA on bulk milk tank (BMT) samples. Associations between possible risk factors (herd size (quartiles)) and herd-level prevalence were determined using chi-squared analysis.

Results

Receiver Operating Characteristics Analysis of replicate results in the preliminary validation study yielded an optimal cut-off PP (Proposed Cut-off percentage positivity - PCO PP) of 7.58%. This PCO PP gave a relative sensitivity (Se) and specificity (Sp) of 98.57% and 100% respectively, relative to the use of the ELISA on individual sera, and was chosen as the optimal cut-off since it resulted in maximization of the prevalence independent Youden’s Index.The herd-level BVD prevalence in non-vaccinating herds was 98.7% (95% CI - 98.3-99.5%) in the cross-sectional study with no significant difference between dairy and beef herds (98.3% vs 98.8%, respectively, p = 0.595).An agreement of 95.4% was found on Kappa analysis of herd serological classification when bulk milk and serum pool results were compared in non-vaccinating herds. 19.2 percent of farmers used BVDV vaccine; 81% of vaccinated herds were dairy. A significant association was found between seroprevalence (quartiles) and herd size (quartiles) (p < 0.01), though no association was found between herd size (quartiles) and herd-level classification based on PCO (p = 0.548).

Conclusions

The results from this study indicate that the true herd-level seroprevalence to Bovine Virus Diarrhoea (BVD) virus in Ireland is approaching 100%. The results of the present study will assist with national policy development, particularly with respect to the national BVD eradication programme which commenced recently.     

Trichinella spiralis infection induces β-actin co-localized with thymosin β4

A serological survey for Neospora caninum and Besnoitia besnoiti was carried out in beef and dairy cattle in South Australia. Serum samples of dairy cattle (n=133) from 9 properties and tank milk samples from a further 122 dairy herds were tested. An additional 810 sera from beef cattle from 51 properties were also tested. Testing at the individual animal level by IDEXX NEOSPORA X2 Ab test ELISA revealed a low prevalence of N. caninum antibodies of only 2.7% (95% CI; 1.6-3.7%) sera positive, as did the milk testing that showed 2.5% (95% CI; 1.4-3.6%) of tank milks being positive. At the herd level, 29.4% (95% CI; 16.9-41.9%) of beef, and 44.4% (95% CI; 12.0-76.9%) of dairy cattle herds showed serum antibodies. The highest within-herd prevalence in beef was 20% and 25%in dairy, which explains the low herd prevalence in dairy detected by bulk milk testing. Testing for B. besnoiti antibodies by PrioCHECK(?) Besnoitia Ab 2.0 ELISA initially identified 18.4% (95% CI: 15.8-21.0%) of 869 individual cattle sera as positive by ELISA at the manufacturer's suggested cut-off threshold (15 PP). Additional tests by immunoblot and IFAT, however, could not confirm any of the ELISA results. The use of a higher (40 PP) threshold in the ELISA is suggested to improve specificity. There is thus no evidence of B. besnoiti infection in South Australian cattle.     

Survey for antibodies to leukemia (C-type) virus in cattle.

Serums from 4,394 dairy cattle in 100 herds and from 2,794 beef cattle in 50 herds were tested for antibody to the bovine (C-type) leukemia virus (BLV), using the agar gel immunodiffusion test. Reactors were found in 66% of the dairy herds (10.2% of the cattle) and in 14% of the beef herds (1.2% of the cattle). The prevalence of reactors was examined with respect to age, herd size, and sex. Few of the reactors were less than 2 years old. There was a high percentage of reactors in small dairy herds (less than 50 cattle). In 22 dairy herds (1,354 cows and 96 bulls), the rate of infection in cows was compared with that in bulls. In those herds, 13.5% of the cows and 10.4% of the bulls were reactors.     

Bovine viral diarrhoea virus in beef cattle herds of Yucatan, Mexico: seroprevalence and risk factors

A survey of bovine viral diarrhoea virus (BVDV) infection was carried out from June 2001 to July 2002 in a non-vaccinated beef cattle population from the livestock region of Yucatan, Mexico, to assess seroprevalence and identify risk factors related to seroprevalence. The aim was also to estimate the intra-herd correlation (r_e) and design effect (D) of BVDV seropositivity. Cattle were selected by a two-stage cluster sampling. Blood samples were collected from 560 animals originating from 40 herds. Sera were tested for antibodies against BVDV using an indirect ELISA test. The sensitivity and specificity of the test was 97.9 and 99.7%, respectively. Risk factors regarding the herd and each animal sampled were recorded through a personal interview at the time of blood sampling. Twenty-four of the 40 herds had at least one seropositive animal. The animal true seroprevalence was estimated as 14%. The marginal logistic regression model used to describe the data found a significant (p < 0.05) association of herd size–cow-origin interaction. The interaction was due to a higher risk of seropositivity in the category of herds with ≤100 animals and purchased cows (OR = 1) as compared to herds with ≤100 animals and cows born in the farm (OR = 0.23). Seropositivity between cows purchased and cows born in the farm was similar for herd sizes of 101–196 and >196 animals. The r_e and D values were 0.17 ± 0.05 and 3.16 ± 0.57, respectively.     

Seroprevalence of Johne's-disease infection in dairy cattle in California,USA

A total of 1,950 serum samples from dairy cattle in California, USA were tested for the presence of antibodies to Mycobacterium avium subspecies paratuberculosis (MAP) using a commercial enzyme-linked immunosorbent assay (ELISA) kit. The sampled animals came from 65 herds and were sampled to reflect the relative numbers and distribution of dairy herds within three geographic regions in the state. Using the manufacturers suggested cut-off for a positive test, 89 animals (4.6%) were positive. The seroprevalence was 6.9% in the northern region of the state, 3.7% in the central region and 5.2% in the southern region. Using the sensitivity and specificity claimed by the manufacturer of the ELISA kit, the true prevalence in California dairy cattle overall was calculated as 9.4% (99% CI, 7.7%, 11.1%) and the true prevalences for the northern, central and southern regions were 14.1% (99% CI, 9.6%, 18.65%), 7.5% (99% CI, 5.6%, 9.4%), and 10.6% (99% CI, 5.9%, 15.6%), respectively.     

Evaluation of a bulk-milk ELISA test for the classification of herd-level bovine leukemia virus status

The results of a commercial bulk-milk enzyme-linked immunosorbent assay (ELISA) test for herd-level bovine leukemia virus (BLV) status were compared to results obtained from individual agar-gel immunodiffussion (AGID) testing on sampled cattle. A positive herd was defined as a herd having one or more AGID-positive animals. The estimated true herd status was based on the sensitivity and specificity of the AGID test and the number of cattle sampled per herd. Ninety-seven herds were used, with a mean of 13 cows sampled per herd. The AGID test indicated an apparent herd prevalence of 70.1%. After accounting for the number of cows sampled and the sensitivity and specificity of the AGID test, the estimated true herd prevalence of BLV was 52.3%. The ELISA test identified 79.4% of herds as positive for BLV, and had an apparent sensitivity and specificity of 0.97 and 0.62, respectively. However, after accounting for the sensitivity and specificity of the AGID test in individual animals, the specificity of the ELISA test was 0.44. The ELISA test was useful for identifying BLV-negative herds (i.e., ruling out the presence of BLV infection in test negative herds). With the moderately low specificity, herds identified as positive by the ELISA test would require further testing at the individual or herd level to definitively establish their BLV status.     

Risk factors for epidemic respiratory disease in Norwegian cattle herds

An epidemic of acute respiratory disease associated with bovine respiratory syncytial virus (BRSV) occurred during the winter and spring of 1995 in two neighbouring veterinary districts in the south-eastern part of Norway.The objective of this study was to describe the time course of the outbreak associated with BRSV in the cattle herds, and to determine the association between selected herd factors and the risk of experiencing a herd outbreak of acute respiratory disease.Data from 431 cattle herds on the dates of disease occurrence, location of the farms, herd size, age profile and production type were collected retrospectively for 1995. The risk of acute respiratory disease occurring in a cattle herd was related to the herd size as well as the type of production, with an expressed interaction between these two variables. From the Cox proportional-hazards model, the risk of a herd outbreak in a mixed herd of 20 animals was estimated to be 1.7-times greater than in a dairy herd and 3.3-times greater than a beef herd (reference category) of a comparable size. On increasing the herd size to 50 animals, the risk increased 1.3-fold for a mixed herd, 3.3-fold for a dairy herd, and 2.1-fold for a beef herd, compared to the risk for a corresponding type of herd of 20 animals.     

Virological and serological evidence of bovine herpesvirus type 4 in cattle in Northern Ireland

Bovine herpesvirus type 4 (BHV-4), a member of the genus Rhadinovirus, subfamily Gammaherpesvirinae, within the family Herpesviridae, was isolated in fetal bovine lung cells from samples of vaginal discharge taken from a dairy herd in which approximately 50 per cent of the cattle developed metritis after calving. The identity of the isolate was confirmed by immunofluorescent staining with a BHV-4-specific monoclonal antibody and partial sequencing of a portion of the glycoprotein B gene. Serological testing failed to demonstrate a significant association between the exposure of the cattle to BHV-4 and the metritis, but several cattle seroconverted during the periparturient period, consistent with the recrudescence and shedding of virus associated with the stresses of parturition and the onset of lactation. Despite the previous failure to detect BHV-4 in Northern Ireland, a serological survey of 999 cattle in 49 dairy herds and 51 beef herds found widespread evidence of exposure: 29 of the dairy herds and 35 of the beef herds contained one or more seropositive cattle, and 33.3 per cent of the dairy cattle and 23.3 per cent of the beef cattle were positive.     

Prevalence of BVDV infection in Greek dairy herds

Thirty-nine Greek dairy herds, totalling 6333 cattle, enrolled in a voluntary bovine viral diarrhoea virus (BVDV) eradication programme based on the identification and removal of persistently infected (PI) animals. The aim of this study was to estimate the prevalences of BVD antigen-positive and PI animals, and investigate the significance of the associations between the prevalence estimates and herd size. Initially, all animals were bled and examined for BVDV, using an antigen ELISA. A second sample was collected from the positive animals, after a period of at least three weeks. Animals retested positive were classified as PI. Antigen positive and PI animals were detected in all herds. The respective mean prevalences, adjusted for the test's accuracy and the herd-clustering effect, were 14% (95%CI: 11-18%) and 1.3% (0.8-1.8%), respectively. Herd size was not associated with the prevalence of antigen-positive or PI animals.