Association of herd BHV-1 seroprevalence with respiratory disease in youngstock in Estonian dairy cattle

Seroepidemiology of bovine alphaherpesvirus 1 (BoAHV-1) in commercial and smallholder dairy herds in north Shewa, central highlands of Ethiopia

Bovine alphaherpesvirus 1 (BoAHV-1) is the most important respiratory and reproductive disease-causing pathogen in dairy cattle. Despite BoAHV-1 has become widespread and a major challenge to the dairy industry, little is known about its epidemiology in dairy herds in Ethiopia. A cross-sectional study was conducted from November 2022 to May 2023 to determine the seroprevalence and potential risk factors associated with BoAHV-1 seropositivity in dairy herds in North Shewa, the central highlands of Ethiopia. A total of 511 blood samples were collected from randomly selected cattle herds (n = 142) and examined antibodies against BoAHV-1 using ELISA test. A retrospective survey was also done to gather information related to reproductive disorders. The overall seroprevalence of BoAHV-1 was 61.84% (95% CI: 57.53-65.97) at the animal level and 85.21% (95% CI: 78.28-90.21) at the herd level. Multivariable logistic analysis revealed that the risk of being BoAHV-1 seropositive was nine times higher in cows older than six years (OR = 9.16; 95% CI: 3.09-27.16; P = 0.000), five times higher (OR = 4.51; 95% CI: 1.23-16.53; P = 0.019) in cows with a history of abortion, three times higher (OR = 2.75; 95% CI: 1.72-4.22; P = 0.029) in cows with a history of retained fetal membrane, and three times higher (OR = 2.83; 1.86-9.31; P = 0.03) in animals with clinical signs of ocular and/or nasal discharge. This study demonstrates a significant circulating of BoAHV-1 in the dairy cattle population in study districts. Thus, a comprehensive approach that includes strict farm biosecurity and vaccination should be practiced for effective BoAHV-1 control and prevention and to promote the growing dairy industry in the central highlands of Ethiopia.

Seroprevalence of selected endemic infectious diseases in large-scale Estonian dairy herds and their associations with cow longevity and culling rates

Herd culling rates and longevity represent herd health and welfare status as well as farm economic performance. The contribution of endemic circulation of the main cattle pathogens to herd performance has not been previously analysed. The aim of this study was to estimate the herd prevalence of selected endemic bovine pathogens among large commercial dairy herds and to analyse their associations with herd culling rates and longevity. Bulk tank milk (BTM) samples and 10 heifer serum samples were collected from 120 Estonian dairy herds with at least 100 cows, between August 2019 and July 2020. All samples were tested for antibodies against bovine herpesvirus 1 (BHV-1), bovine viral diarrhoea virus (BVDV), bovine respiratory syncytial virus (BRSV), Mycoplasma bovis, Mycobacterium avium spp. paratuberculosis (MAP) and Salmonella Dublin using commercial ELISA. Data on herd size, milk yield, culling rate (CR) and mean age of the culled cows (MAofCC) were collected from the Estonian Livestock Performance Recording Ltd. The apparent herd and animal prevalences were calculated, and linear regression models were used to identify associations between the herd status of six tested pathogens and CR and MAofCC. The herd seroprevalences for antibodies based on BTM and heifer serum sample testing were BHV-1 56.7 % (95 % CI 47.3; 65.7), Mycoplasma bovis 48.3 % (95 % CI 39.1; 57.6), MAP 2.5 % (95 % CI 0.5; 7.1) and S. Dublin 24.2 % (95 % CI 16.8; 32.8) in all tested herds. Excluding vaccinated herds, herds prevalence for BVDV was 27.0 % (95 % CI 19.0; 36.3) and for BRSV 94.7 % (95 % CI 88.1; 98.3). Herd seropositive status for BRSV was associated with lower MAofCC, and herds with BSRV-seropositive youngstock had increased CR. Herds with positive BTM test results for S. Dublin culled cows at an older average age (Coef = 3.79 months, 95 % CI 0.52; 7.07, p = 0.023). MAP-positive herds had somewhat lower herd MAofCC (Coef = -6.18 months, 95 % CI -12.98; 0.63, p = 0.075). There was also a tendency of BVDV-negative herds to have a lower CR than BVDV-positive herds (Coef = -3.03 %, 95 % CI -6.54; 0.49, p = 0.090), and vaccination against BVDV tended to be protective against high CR (Coef = -6.26 %, 95 % CI -12.61; 0.09, p = 0.053 compared to infected herds). This study shows that Estonian large-scale dairy herds are endemically infected with several important cattle pathogens. Most of the studied pathogens influence longevity and culling rates, thus entailing health and economic consequences.

Increased incidence rate of undesired early heifer departure in Mycoplasma bovis-antibody positive Danish dairy cattle herds

Mycoplasma bovis infections cause disease and production losses in cattle worldwide. The long-term consequences are not well described despite being important for management decisions during and after disease outbreaks. We investigated the association between M. bovis antibody-positivity and undesired early departure (UED, i.e. death, euthanasia or slaughter) before first calving in a cohort of 636 heifers from 36 Danish dairy herds with and without a history of M. bovis-associated disease. The herds were visited 4 times at 3-month intervals and blood samples from young stock and milk samples from lactating cows were collected. Poisson regression was performed to examine the association with UED as outcome, logarithmic transformation of risk time as offset and herd as a random effect. Individual antibody measurements and group-level variables representing the infection level among young stock and cows, age and mortality variables were included in the model. The incidence rate ratio of UED increased by 1.23 times for every 10% increase in M. bovis young stock seroprevalence, while the effect of individual antibody level was modified by age and influenced UED less. In conclusion, UED in heifers was associated with M. bovis antibody-positivity in young stock and should be controlled in dairy herds to reduce losses.

Phylogenetic analysis of glycoprotein B gene sequences of bovine herpesvirus 1 isolates from India reveals the predominance of subtype 1.1

AIM

This study was conducted for the isolation and molecular characterization of bovine herpesvirus 1 (BoHV-1) isolated from the nasal and vaginal swabs collected from naturally infected cattle showing clinical symptoms of the respiratory disease.

MATERIALS AND METHODS

Isolation of BoHV-1 virus performed on clinical samples collected from 65 cattle from five states of India. The BoHV-1 isolates were further confirmed by polymerase chain reaction (PCR) using primers specific for glycoprotein B (gB) genomic region. PCR amplification was performed using previously published gB gene-specific primer pairs. gB PCR amplicons obtained from all isolates were sequenced, and phylogenetic analysis was performed using software.

RESULTS

A total of 12 samples were found positive in cell culture isolation. 11 isolates showed the visible cytopathic effect on Madin-Darby bovine kidney after 72 h. Partial sequence analysis of gB gene of all isolates revealed 99.0-100% homology between them. All isolates showed 99.2-99.8% homology with Cooper stain.

CONCLUSION

BoHV-1.1 is the predominant circulating subtype of BoHV in India, and all isolates have homology with Cooper stain.

Bovine herpes virus-1 (BoHV-1) in cattle-a review with emphasis on reproductive impacts and the emergence of infection in Ireland and the United Kingdom

Bovine reproductive disease attributable to bovine herpes virus-1 (BoHV-1) was first described in Germany in the 19th century, being recognised primarily as the cause of infectious vulvovaginitis and balanoposthitis until the mid-1950s when a more virulent strain of the virus (BoHV-1.1) associated with respiratory disease (infectious bovine rhinotracheitis; IBR) emerged in the western United States. Subsequently, IBR emerged as a clinical condition in Europe, from the 1970s onward. While the ability of BoHV-1 to produce respiratory disease is now well recognised, the potential negative outcomes of infection on fertility and reproduction are less frequently considered. This review was conducted against the background of the prioritization of disease caused by BoHV-1 as one of several diseases to be addressed by Animal Health Ireland, with the twin goals of summarizing the published literature on the potential outcomes of infection at different stages of breeding and pregnancy, and of describing the emergence of BoHV-1 as a significant pathogen in Ireland and the UK.

Epidemiology, molecular epidemiology and evolution of bovine respiratory syncytial virus

The bovine respiratory syncytial virus (BRSV) is an enveloped, negative sense, single-stranded RNA virus belonging to the pneumovirus genus within the family Paramyxoviridae. BRSV has been recognized as a major cause of respiratory disease in young calves since the early 1970s. The analysis of BRSV infection was originally hampered by its characteristic lability and poor growth in vitro. However, the advent of numerous immunological and molecular methods has facilitated the study of BRSV enormously. The knowledge gained from these studies has also provided the opportunity to develop safe, stable, attenuated virus vaccine candidates. Nonetheless, many aspects of the epidemiology, molecular epidemiology and evolution of the virus are still not fully understood. The natural course of infection is rather complex and further complicates diagnosis, treatment and the implementation of preventive measures aimed to control the disease. Therefore, understanding the mechanisms by which BRSV is able to establish infection is needed to prevent viral and disease spread. This review discusses important information regarding the epidemiology and molecular epidemiology of BRSV worldwide, and it highlights the importance of viral evolution in virus transmission.