Uterine infection with bovine herpesvirus type 4 in dairy cows

Diseases of the reproductive tract are a frequent problem in dairy herds. Herpesviruses are uterine pathogens also involved in other clinical diseases; for example, bovine herpesvirus type 4 BoHV‐4 induces abortion, enteritis, metritis, pneumonia and vaginitis, but it can also be detected in healthy cows. The role of BoHV‐4 in the development of clinical endometritis (CE) or subclinical endometritis (SE) has not clearly been described. Therefore, the objective of this study was to describe the prevalence of uterine BoHV‐4 infection and its relationship with clinical, bacteriological and cytological findings in dairy cows 20–30 days after calving. The experiment was performed as a completely randomized block design, with farm (n = 10) as blocking criterion and with cow (n = 397) as the experimental unit. Logistic regression models were used to assess the effect of BoHV‐4 infection on CE, SE and reproductive performance. Proportion of cows infected with BoHV‐4 was 5.8% (n = 23/397). BoHV‐4 was isolated in 11.0% (n = 12/109), 4.8% (n = 4/84) and 3.6% (n = 7/194) of cows diagnosed as CE, SE or healthy, respectively. A logistic model revealed that BoHV‐4 infection showed a tendency to increase the risk for CE (AOR = 2.17; p = .10) but significantly reduced both, the odds for artificial insemination within 80 days post‐partum (dpp) (AOR = 0.37; p = .035) and for pregnancy within 200 dpp (AOR = 0.13; p = .004). Furthermore, BoHV‐4 infection increased the chance for intrauterine infection with Trueperella pyogenes (AOR = 5.55; p < .001) and vice versa (AOR = 5.79, p < .001). In conclusion, BoHV‐4 infection is associated with reduced chances for insemination and pregnancy by 200 dpp and showed a trend to be associated with increased risk for CE. Furthermore, BoHV‐4 and Trueperella pyogenes infections are strongly related.     

Prevalence of bovine herpesvirus 1 (BHV-1) infection in Hungarian cattle herds.

Hungarian cattle herds were surveyed for bovine herpesvirus 1 (BHV-1) infection by ELISA of milk and serum samples. In 1993, 75% of the large cattle herds (consisting of more than 50 cattle) and all small herds (small-scale producers' stocks), while in 1997 90% of the small herds were included in the survey. In the case of large herds, 79.3% of the herds and 64.1% of the samples tested were found to be positive. Of the small herds, 13.5% and 15.7% tested positive in 1993 and 1997, respectively. The majority of large herds were Holstein-Friesian dairy stocks. Small herds with an infection rate markedly exceeding the average were found in those counties where the small herds had been in close contact with the large-scale farms, or where new herds were established by using animals of uncontrolled infectious bovine rhinotracheitis (IBR) status originating from large farms. Attention is called to the importance of maintaining the IBR-free status of small herds that constitute one-third of the Hungarian cattle population.     

Serological survey of bovine herpesvirus type 1 infection in China

To understand the nationwide seroprevalence of bovine herpesvirus type 1 (BoHV-1) infection of cows in China, 1344 sera of dairy cows from 29 provinces and 765 sera from 6 herds in Hubei province were collected with stratified random sampling. Another 483 sera from imported cows were included. The serum antibody was tested by BoHV-1 gG ELISA. The results demonstrated that the overall nationwide seroprevalence was 35.8% (481/1344), while the prevalence for individual province ranged from 12.1% to 77.8%. Although each province had positive samples, the prevalence was clustered in areas based on the cow population size. In Hubei Province, the overall seroprevalence was 22.2% (170/765) while the prevalence for individual farms varied greatly from 0.0% to 41.5%. The sera from imported cows had a moderate prevalence of 21.7% (105/483).     

Prevalence and control of bovine cryptosporidiosis in German dairy herds

In a 5-year survey regarding its prevalence and importance in five German state veterinary laboratories Cryptosporidium was diagnosed annually in 19-36% of faecal samples either submitted to the laboratories or taken post mortem. In approximately half of the cases no other enteropathogens were detected. However, only 73% of 30 laboratories participating in a questionnaire survey routinely tested for this parasite, and the majority of researchers considered cryptosporidiosis to be of minor importance. In a placebo-controlled field study 152 suckling calves were treated daily against cryptosporidiosis either with sulfadimidine or with halofuginone (Halocur, Intervet) over 1 week. Treatment by oral drench started at the onset of diarrhoea in the herd. Oocyst excretion, faecal consistency and health status were recorded five times for a 3-week period. Oocyst excretion peaked 7-14 days in the placebo group after the onset of diarrhoea, and during that period prevalence and intensity of excretion were significantly lower in the halofuginone-treated group compared to the sulfadimidine and the placebo control groups. The health status (diarrhoea, dehydration) declined in all groups but was significantly (P<0.05-0.001) better in the halofuginone group in the first 2 weeks. Halofuginone effectively (P<0.05-0.001) reduced oocyst excretion and improved the health status of the treated animals, while sulfadimidine had no effect against Cryptosporidium.     

Detection of bovine herpesvirus type 4 antibodies and bovine lymphotropic herpesvirus in New Zealand dairy cows

AIM: To detect the presence of bovine herpesvirus (BoHV) type 4 in New Zealand dairy cows with clinical metritis.

METHODS: Serum samples taken from 92 dairy cows with clinical metritis, each from a different farm, were tested for the presence of antibodies against BoHV-4 using a commercially available, indirect ELISA. Peripheral blood mononuclear cells (PBMC) were collected from 10 BoHV-4 seropositive cows, and PBMC were examined by a pan-herpesvirus nested PCR to detect herpesvirus. PCR products were sequenced directly and a proportion of the PCR products were cloned and sequenced to identify the virus present.

RESULTS: Antibodies to BoHV-4 were detected in 23/92 (25%) serum samples. The pan-herpesvirus PCR was positive in 8/10 PBMC samples. Cloning and sequencing identified that all of the eight PCR-positive PBMC contained bovine lymphotropic herpesvirus (BLHV); no BoHV-4 DNA was detected.

CONCLUSIONS: This study reports the finding of the presence of apparent antibodies to BoHV-4, and BLHV DNA in New Zealand dairy cows affected by metritis.

CLINICAL RELEVANCE: Bovine herpesvirus type 4 and BLHV are reported to have the potential to cause reproduction failure in cows. This is the first report of apparent BoHV-4 antibodies, and BLHV in New Zealand. The importance and epidemiology of these viruses in cattle in New Zealand requires further investigation.     

Aspects of bovine herpesvirus 1 and bovine viral diarrhoea virus herd-level seroprevalence and vaccination in dairy and beef herds in Northern Ireland

Background

Infections with bovine herpesvirus 1 (BoHV-1) and bovine viral diarrhoea (BVD) virus cause diseases of cattle with a worldwide distribution. The primary objective of the present study was to describe aspects of herd-level BoHV-1 and BVDV seroprevalence (based on testing of pooled sera) and control on farms in Northern Ireland, including vaccine usage.An indirect antibody ELISA test (SVANOVA, Biotech AB, Uppsala, Sweden) was applied to serum pools which were constructed from serum samples taken for a cross-sectional study of a convenience sample of 500 Northern Irish dairy and beef cow herds in 2010, for which vaccination status was determined by telephone survey. The herd-level seroprevalence of BoHV-1 and BVDV in Northern Ireland was estimated in non-vaccinating herds and associations between possible risk factors (herd type and herd size (quartiles)) and herd-level prevalence were determined using chi-squared analysis.

Results

The herd-level seroprevalence (of BoHV-1 and BVDV) in non-vaccinating herds was 77.3% (95% CI: 73.6–80.9%) and 98.4% (95% CI: 97.3–99.5%) respectively in the cross-sectional study. A significant difference existed in BoHV-1 herd-level seroprevalence between dairy and beef herds (74.7% vs 86.5% respectively; p < 0.02) though not for BVDV seroprevalence (98.5% vs 98.3% respectively; p > 0.91). A significant association was found between herd size (quartiles) and herd-level classification for BoHV-1 herd-level seroprevalence based on cut-off percentage positivity (COPP) (p < 0.01) while no such association was found for BVDV (p = 0.22).15.5% and 23.8% of farmers used BoHV-1 and BVDV vaccines, respectively. BoHV-1 vaccine was used in 30% of dairy herds and in 11% of beef herds, while BVDV vaccine was used in 46% and 16% of dairy and beef herds, respectively.

Conclusions

The results from this study indicate that the true herd-level seroprevalences to bovine herpesvirus 1 and bovine virus diarrhoea virus in non-vaccinating herds in Northern Northern Ireland are 77.3% (95% CI: 73.6–80.9%) and 98.4% (95% CI: 97.3–99.5%), respectively. The present study will assist in guiding regional policy development and establish a baseline against which the progress of current and future control and eradication programmes can be measured.     

Economic implications of bovine leukemia virus infection in mid-Atlantic dairy herds

OBJECTIVE: To determine the baseline costs of bovine leukemia virus (BLV) infection, including costs of clinical disease and subclinical infection, in a dairy herd representative of the mid-Atlantic region and compare these costs with the cost of a test-and-manage BLV control program. DESIGN: Stochastic spreadsheet model. SAMPLE POPULATION: A commercial Holstein dairy herd with 100 milking cows. PROCEDURES: A spreadsheet model was developed. The overall cost of infection included the cost of clinical disease (ie, lymphosarcoma [LS]) and the effects of subclinical infection on milk production and premature culling. Model input values and distributions were designed to reflect economic conditions in the mid-Atlantic region. Relative costs of infection and control were calculated for infection prevalences of 20, 50, and 80%. RESULTS: Estimated mean cost to the producer per case of LS was 412 dollars; for a herd with a 50% prevalence of BLV infection, annual incidence of LS was 0.66. Mean annual cost of subclinical infection at a 50% prevalence of infection was 6,406 dollars. Mean annual cost of a test-and-manage control program was 1,765 dollars. The cost of clinical disease and subclinical infection varied substantially with the prevalence of infection, whereas the cost of control varied with herd size. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that a basic BLV control program may be economically beneficial in herds in which the prevalence of BLV infection is > or = 12.5%. Farm-specific considerations may factor prominently when weighing the costs and benefits of an individual BLV control program.     

Aspects of bovine herpesvirus-1 infection in dairy and beef herds in the Republic of Ireland

Background

Infection with bovine herpesvirus-1 (BHV-1) causes a wide range of disease manifestations, including respiratory disease and abortion, with world-wide distribution. The primary objective of the present study was to describe aspects of BHV-1 infection and control on Irish farms, including herd-level seroprevalence (based on pooled sera) and vaccine usage.

Methods

The characteristics of a diagnostic indirect BHV-1 antibody ELISA test when used on serum pools were evaluated using laboratory replicates for use in the seroprevalence study. The output from this indirect ELISA was expressed as a percentage positivity (PP) value. A proposed cut off (PCO) PP was applied in a cross-sectional study of a stratified random sample of 1,175 Irish dairy and beef cattle herds in 2009, using serum pools, to estimate herd seroprevalence. The study was observational, based primarily on the analysis of existing samples, and only aggregated results were reported. For these reasons, ethical approval was not required. Bulk milk samples from a subset of 111 dairy herds were analysed using the same ELISA. Information regarding vaccine usage was determined in a telephone survey.

Results

A PCO PP of 7.88% was determined to give 97.1% sensitivity and 100% specificity relative to the use of the ELISA on individual sera giving maximization of the prevalence independent Youden''s index, on receiver operating characteristics analysis of replicate results. The herd-level BHV-1 seroprevalence was 74.9% (95% CI - 69.9%-79.8%), with no significant difference between dairy and beef herds. 95.5% agreement in herd classification was found between bulk milk and serum pools. Only 1.8 percent of farmers used BHV-1 marker vaccine, 80% of which was live while 75% of vaccinated herds were dairy.A significant association was found between herd size (quartiles) and seroprevalence (quartiles).

Conclusions

The results from this study indicate BHV-1 infection is endemic, although BHV-1 vaccines are rarely used, in the cattle population in Ireland.     

Dynamics of natural bovine herpesvirus-1 (BoHV-1) infection in a dairy herd

In this study, natural cycling of BoHV-1 infection was investigated in two groups of dairy cattle containing 2120 head. Group 1 comprised 127 animals and they were monitored for BoHV-1 infection virologically and serologically in six consecutive sampling periods. It consisted of naive heifers between 6 and 8 months of age, while in group 2, age, sex and the BoHV-1 serostatus of the animals were disregarded. The animals in group 1 were found to have seroconverted at the second sampling. Results of the serological study showed slight antibody response after natural BoHV-1 infection in the herd and neutralizing titres fell below protective levels in the 6–8 months after the peak. During the 2-year study period, one recurrence was detected after primary infection. Virus isolation studies revealed a cytopathic effect indicative of BoHV-1 in two nasal swabs taken during the fifth sampling period from animals with mild upper respiratory tract symptoms. As the study was carried out under natural conditions, it is not known whether the viruses isolated were from recurrences or re-infections. Data from cross-neutralization tests with herd isolates showed higher antibody response than those with the reference virus. The dynamics of BoHV-1 in both groups were found to be statistically similar.     

A serological survey of bovine herpesvirus-1 infection in selected dairy herds in northern and central Italy

Serum samples from a total of 6979 dairy cattle from 55 herds in northern Italy (51 herds) and central Italy (4 herds), were examined by the serum neutralization test for the presence of antibody to bovine herpesvirus-1 (BHV-1). It was found that 84.31% of the farms selected in northern Italy and all the farms from central Italy had seropositive animals at titers of 1:4 or higher. The prevalence of infection was essentially the same among the cattle populations of the two selected areas of the country, being of 34.99% in the north and of 38.65% in central regions. A comparison of the data from the present study with those obtained in a serological survey conducted in Italy in 1966, shows that the rate of seropositive cattle to BHV-1 has increased by about 5.0% in the last 30 years.     

Hemagglutinating activity associated with bovine herpesvirus type 1

Using C57BL/HPB mouse erythrocytes, hemagglutination has been observed with the Los Angeles and Colorado-1 strains of bovine herpesvirus type 1 and with 12 other Canadian field isolates as well. The specificity of the hemagglutination observed with the viral strains has been confirmed by a hemagglutination-inhibition assay.     

Analysis of bovine trigeminal ganglia following infection with bovine herpesvirus 1

Following primary infection of the eye, oral cavity, and/or nasal cavity, bovine herpesvirus 1 (BHV-1) establishes latency in trigeminal ganglionic (TG) neurons. Virus reactivation and spread to other susceptible animals occur after natural or corticosteroid-induced stress. Infection of calves with BHV-1 leads to infiltration of lymphocytes in TG and expression of IFN-gamma (interferon-gamma), even in latently infected calves. During latency, virus antigen and nucleic acid positive non-neural cells were occasionally detected in TG suggesting there is a low level of spontaneous reactivation. Since we could not detect virus in ocular or nasal swabs, these rare cells do not support high levels of productive infection and virus release or they do not support virus production at all. Dexamethasone (DEX) was used to initiate reactivation in latently infected calves. Foci of mononuclear or satellite cells undergoing apoptosis were detected 6h after DEX treatment, as judged by the appearance of TUNEL+ cells (terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling). BHV-1 antigen expression was initially detected in lymphocytes and other non-neural cells in latently infected calves following DEX treatment. At 24h after DEX treatment, viral antigen expression and nucleic acid were readily detected in neurons. Our data suggest that persistent lymphocyte infiltration and cytokine expression occur during latency because a low number of cells in TG express BHV-1 proteins. Induction of apoptosis and changes in cytokine expression following DEX treatment correlates with reactivation from latency. We hypothesize that inflammatory infiltration of lymphoid cells in TG plays a role in regulating latency.     

Frequency of bluetongue and bovine parvovirus infection in cattle in South Carolina dairy herds

A survey of South Carolina diary cattle in 12 commercial herds was conducted, using serologic testing to determine the frequency and impact on reproduction of bluetongue (BT) and bovine parvovirus (BFV) infections. Results of the study of serum antibodies titers and dairy cattle health records indicated that the majority of the cattle surveyed was adequately protected against the major reproductive tract diseases through vaccination programs. The frequency of reproductive dysfunction was common in vaccinated herds, however. Six of the 12 herds in the survey had cattle which were BT serotest reactors, although total numbers of these reactor cattle were relatively small. Further, reproductive performance of reactor cows indicated that BT was of little consequence and was not associated with reproductive problems. All herds contained BPV serotest reactors and the latter comprised 59.7% of the total number of cows surveyed. The BPV seroreactor cows were commonly associated with the group of reproductive problem cows which experienced higher rates of embryonic mortality and more services per conception than did nonreactor cattle. The results of the survey emphasize the need for continued investigation and efforts to control BT, and especially BPV infection, in dairy cattle.     

Prevalence and risk factors associated with bovine viral diarrhea virus infection in dairy herds in Jordan

A cross-sectional study was carried out to determine the seroprevalence and to identify risk factors associated with bovine viral diarrhea virus (BVDV) infection in 62 non-vaccinated dairy herds (671 cows) in Jordan between January and June 2007. Information regarding herd management was recorded through a personal interview with farmers. Antibodies against BVDV were detected using an indirect ELISA test. Chi-square analysis and multivariable logistic regression model were used to identify risk factors for BVDV seropositivity. The true prevalence of antibodies against BVDV in individual cows and cattle herds was 31.6% and 80.7%, respectively. The seroprevalence of BVDV in medium and large size herds was significantly higher than that in smaller herds. There was no significant difference in BVD seroprevalence between different age groups. Random-effects logistic regression model revealed two major factors associated with seropositivity to BVDV; exchange of visits between adjacent farm workers and not isolating newly purchased animals before addition to the herd. The seroprevalence of BVDV in cows located in the northern Jordanian governorates was significantly higher than that in other studied governorates. Results of this study indicated that BVDV is highly prevalent in Jordan and BVDV infection could be controlled by livestock-trade control, and applying strict biosecurity measures in the dairy farms.     

Spatial differences in occurrence of paratuberculosis in Danish dairy herds and in control programme participation

Paratuberculosis is a chronic infection of economic importance to the cattle industry and a voluntary control programme is offered to Danish dairy farmers. Our objective was to evaluate spatial differences in both control programme participation and paratuberculosis prevalence in Denmark. The study included 4414 dairy herds: 1249 were participating in the control programme, and 1503 were tested for antibodies to Mycobacterium avium subsp. paratuberculosis (MAP). Spatial differences were evaluated by kernel smoothing, kriging, and cluster analysis. Participation was lowest among herds on the island Zealand (≤23%). The risk of a herd being infected with MAP was found to be high on most of Zealand, but the uncertainty of this result was large due to a limited number of tested herds. In the rest of the country, the south western part of the peninsula Jutland had the highest risk of MAP (≥91%). The risk of MAP was also high (86-91%) in the northern part of both Jutland and Funen. The predicted apparent within-herd prevalence was highest (5-8.5%) in some local areas across Jutland, in the north western part of the island Funen, and in the south and western part of Zealand. Scan statistics located the primary cluster of herds with high apparent within-herd prevalence in the western part of Funen. Furthermore, a number of significant clusters were found in Jutland and a single significant cluster in Zealand. Consistency was found between kriging and scan statistics results with respect to location of areas with high apparent within-herd prevalence of MAP. Potential explanations for differences in participation include herd size and local herd health advisers, whereas for example soil characteristics might influence prevalence. Further studies are needed to evaluate these and other risk factors.     

Persistent infection of bovine herpesvirus type 4 in bovine endothelial cell cultures

Herpesviruses can establish a persistent infection in the cells and tissues of their natural hosts and thus may produce diseases due to cytolytic infections. We have isolated a herpesvirus from a bovine vascular endothelial cell culture after continuous subculturing. Typical cytopathic changes were observed in bovine endothelial cell cultures 2 days after inoculation of the virus. The virus had an icosahedral nucleocapsid of 100-150 nm in diameter and an envelope. The sequences of some DNA fragments of the virus were highly homologous to those of the bovine herpesvirus type 4 (BHV-4) strains. The DNA restriction maps of the virus and the reference strains of BHV-4, DN 599 and Movar 33/63 were very similar but not identical. Therefore, the newly isolated virus has been designated Taiwan strain. The presence of BHV-4 DNA in apparently normal bovine endothelial cell cultures was shown by Southern blot hybridization with the BamHI fragment of the newly isolated BHV-4 and was further confirmed by digestion of the DNA with BamHI plus AccI. In conclusion, we have demonstrated that BHV-4 persisted in the bovine endothelial cell cultures and continuous subcultures could lead to the production of infectious viral particles.     

Control and eradication programme of enzootic bovine leucosis (EBL) from selected dairy herds in Turkey

Serum samples of 15,909 cattle from 31 dairy herds located in various regions of Turkey were tested for the presence of antibodies against bovine leucosis virus (BLV) using Agar Gel Immuno-diffusion technique (AGID). 48.3% (15/31) of the herds had seropositive animals and positivity rates were detected from 0.5-34.4% in these herds. In an EBL control/eradication programme all seropositive animals were culled in the infected herds. Thereafter, a total of 74,347 sera were tested for the presence of BLV specific antibodies. The serological results and detail of EBL control/eradication programme were shown in this paper.     

Outbreak of bovine virus diarrhea on Dutch dairy farms induced by a bovine herpesvirus 1 marker vaccine contaminated with bovine virus diarrhea virus type 2

On 23 February 1999, the Dutch Animal Health Service advised all Dutch veterinary practices to postpone vaccination against bovine herpesvirus 1 (BHV1) immediately. The day before severe disease problems were diagnosed on four dairy farms after vaccination with the same batch of BHV1 marker vaccine. Using monoclonal antibodies, bovine virus diarrhoea virus (BVDV) type 2 was found in the vaccine batch. This paper describes an outbreak of BVDV type 2 infection caused by the use of a batch of modified live BHV1 marker vaccine contaminated with BDVD. Sources of information used were reports of farm visits, minutes of meetings, laboratory results, and oral communications from the people involved. The first symptoms of disease were observed on average six days after vaccination. Morbidity was high on 11 of the 12 farms. On five farms more than 70% of the animals became ill, while on one farm no symptoms could be detected. During the first week after vaccination, feed intake and milk production decreased. During the second week, some animals became clinically diseased having nasal discharge, fever, and diarrhoea. At the end of the second week and at the start of the third week, the number of diseased animals increased rapidly, the symptoms became more severe, and some animals died. Mortality varied among herds. Necropsy most often revealed erosions and ulcers of the mucosa of the digestive tract. In addition, degeneration of the liver, hyperaemia of the abomasum, and swollen mesenterial lymph nodes and swollen spleen were found. On 11 of the 12 farms all animals were culled between 32 and 68 days after vaccination after an agreement was reached with the manufacturer of the vaccine. This was the third outbreak of BVD in cattle after administration of a contaminated vaccine in the Netherlands. The possibilities to prevent contamination of a vaccine as a consequence of infection of fetal calf serum with BVDV are discussed. Improvement of controls to prevent contamination before and during vaccine production, and improvement of the monitoring of side-effects is necessary.     

Dynamics of virus infections involved in the bovine respiratory disease complex in Swedish dairy herds

The dynamics of bovine respiratory syncytial virus (BRSV), bovine parainfluenza virus 3 (PIV-3), bovine corona virus (BCoV) and bovine viral diarrhoea virus (BVDV) infections were studied in 118 dairy herds in south western Sweden. By using serology on paired samples from three approximately 7 vs. approximately 15-month-old calves per herd, the propagation of infections was investigated over about a 1-year period. The results implied that at least 74% of calves had experienced one or more of the monitored infections at the age of approximately 7 months (Sample 1, Spring); 30%, 48%, 34% and 8% were seropositive to BRSV, PIV-3, BCoV and BVDV, respectively. Seroconversions to BRSV, PIV-3, BCoV and BVDV occurred in 26%, 38%, 50% and 3% of seronegative animals and 63% had antibodies against two or more infections at approximately 15 months (Sample 2). In total, 90-97% of animals that were seropositive in Sample 1 remained positive in Sample 2. A significant association was found between BVDV and BCoV (P = 0.01). Moreover, a significantly higher proportion of herds in which no calves had a recorded history of respiratory disease (n = 15) were classified as negative to all four infections monitored when compared to herds in which disease was observed (P = 0.0002). This study showed a high infection burden in young animals and effective spread of BRSV, PIV-3 and BCoV in one area of Sweden. BVDV infections were restricted to a few herds, reflecting the effect of a voluntary control program against BVDV in Sweden.