Cattle Herpesvirus Surveillance Reveals Seasonal Patterns and Genetic Diversity in the UK and India

Bovine alphaherpesvirus 1, known widely by its abbreviation BoAHV-1, remains one of the most consequential viral pathogens of cattle worldwide, and a new surveillance study from the United Kingdom and India has now provided one of the most detailed recent pictures of its activity in clinical respiratory disease and in the semen trade. Writing in Virology Journal, a team led by Meenakshi Khatri and Akbar Dastjerdi of the Animal and Plant Health Agency (APHA)-Weybridge, together with collaborators at the National Dairy Development Board R&D Laboratory in Hyderabad, reports the results of a systematic testing programme that ran from November 2022 to March 2025 as part of routine cattle disease surveillance in England and Wales. The work combined molecular diagnostics, epidemiological analysis and phylogenetics to address three linked questions: how often the virus contributes to outbreaks of bovine respiratory disease, when those contributions peak across the year, and how the circulating strains relate genetically to each other and to isolates from a very different cattle population on another continent.

The scale of the testing effort gives the findings considerable weight. In total, 1,040 clinical respiratory samples collected from cattle were screened by quantitative polymerase chain reaction (qPCR), a technique that detects and quantifies viral DNA directly in clinical material rather than relying on antibody evidence of past exposure. Alongside these, the team examined seven semen isolates originating from India, a material addition because BoAHV-1 can be transmitted through semen and therefore poses a direct risk to international trade and to breeding programmes. Semen screening is mandatory for virus control in many jurisdictions, and the Indian isolates analysed in this study came from frozen semen doses sourced from bulls that were seropositive for infectious bovine rhinotracheitis, the clinical syndrome caused by BoAHV-1, and were submitted for mandatory real-time PCR screening.

The headline detection figure was 5 percent: fifty-two of the 1,040 respiratory samples tested positive for BoAHV-1 DNA. While that proportion may appear modest, it represents a meaningful share of the respiratory disease burden captured by the surveillance system, because bovine respiratory disease complex, or BRDC, is typically multifactorial. Several pathogens act alone or in combination, alongside stressors such as transport, weaning and housing changes, to produce the pneumonia and upper respiratory signs that make BRDC the most economically significant disease syndrome of intensively managed cattle. Establishing the contribution of any single agent requires exactly the kind of sustained, standardised testing that this programme provided, and the authors note that BoAHV-1 remains one of the main primary pathogens involved in the syndrome in the United Kingdom, where respiratory disease caused by this virus is termed infectious bovine rhinotracheitis, or IBR.

One of the most practically useful outputs of the study is its seasonal picture. The number of BoAHV-1 positive cases remained relatively stable across the two-and-a-half-year study period, but detection rates were higher in late autumn and fell to a minimum in late summer and early autumn. This pattern is consistent with the known ecology of respiratory pathogens in temperate cattle systems, where the movement of animals indoors, the mixing of age groups and the resulting close contact create conditions favourable for viral transmission as the weather turns. For veterinarians and herd health planners, the timing matters: vaccination campaigns, biosecurity measures and diagnostic vigilance can be concentrated in the weeks when the risk of IBR outbreaks is greatest, and the stability of the annual pattern over the study period suggests that this seasonality is a reliable feature rather than a one-off artefact of a single unusual year.

The qPCR data also revealed that BoAHV-1 rarely acts in isolation. The study detected co-infections involving bovine respiratory syncytial virus (BRSV), bovine parainfluenza virus 3 (PIV3) and bovine coronavirus (BCoV) alongside BoAHV-1. This finding underscores a central principle of BRDC epidemiology: viral co-infections are common and may compound each other’s effects, damaging the respiratory epithelium, impairing mucosal immunity and opening the door to secondary bacterial pneumonia. For diagnostic laboratories, the message is that testing for a single agent risks underestimating the complexity of an outbreak, and panels covering the major viral contributors, including BoAHV-1, BRSV, PIV3 and BCoV, provide a far more complete picture of what is actually circulating in a affected herd.

Beyond counting cases, the study made a substantive contribution to viral genotyping methodology. BoAHV-1 strains are classified into subtypes, and the International Committee on the Taxonomy of Viruses (ICTV) recommends particular genes for phylogenetic analysis to assign strains to those subtypes. The team compared phylogenetic trees generated using the ICTV-recommended genes with trees built from the UL44 gene, which encodes a DNA polymerase processivity factor, and specifically its carboxy-terminal region. The goal was to simplify and validate a UL44-based genotyping scheme, and the comparison delivered a clear verdict: UL44 genotyping produces phylogenies comparable to those obtained with the full set of ICTV-recommended genes. A single, shorter locus that faithfully reproduces the classification obtained from multiple genes is a valuable practical tool, reducing sequencing cost and turnaround time for laboratories that need to subtype isolates quickly during outbreak investigations or trade screening.

The phylogenetic analysis of the UK clinical samples produced findings of both confirmatory and exploratory value. All BoAHV-1 sequences obtained from respiratory samples collected from UK herds fell into subtypes 1.1 and 1.2, with the majority belonging to subtype 1.1. This is consistent with the known dominance of subtype 1.1 in western European cattle populations. More intriguingly, the UK subtype 1.1 viruses were staggered along the phylogenetic branches rather than clustering tightly together, a pattern that suggests multiple lineages circulating within the national cattle population rather than a single homogeneous strain. Such structure can arise from repeated introductions through animal movements, from the long-term local evolution of lineages established in the past, or from the widespread use of live vaccines, which are deployed extensively across the UK cattle industry to control IBR and which the authors highlight as a reason why monitoring disease occurrence alongside vaccine use is important.

The seven Indian semen isolates added a genuinely novel dimension. Although they also grouped within subtype 1.1, they formed distinct branches on the phylogenetic trees, separate from the UK sequences. The authors interpret this as indicating possible divergent evolution of the virus in Bos indicus, the humped zebu cattle that dominate much of South Asian livestock, or in their crossbreeds. If BoAHV-1 lineages are adapting to or co-evolving with a different host subspecies, the global genetic diversity of the virus may be considerably greater than the datasets derived from European and North American cattle suggest. That possibility has direct practical consequences, because the efficacy of currently available vaccines in Asian and African countries could be affected by antigenic differences between locally circulating strains and the strains against which those vaccines were developed, a gap in knowledge the study explicitly highlights.

The collaborative framework behind the work is itself noteworthy. The research was funded by the Department for Environment, Food and Rural Affairs and the Welsh Government through the Scanning Surveillance for Diseases in Cattle in England and Wales project at APHA, and by the National Dairy Development Board in Anand, India. It was achieved through a World Organisation for Animal Health (WOAH) twinning project between APHA-Weybridge and the NDDB R&D Laboratory, a mechanism designed to build laboratory capacity and share expertise between institutions in different countries. The samples themselves depended on the cooperation of APHA and private veterinarians and, crucially, of farmers, whose participation in surveillance schemes of this kind is often underappreciated. Tissue samples used in the study were obtained from animal carcasses and required no ethical approval, while other samples were collected for clinical purposes under the Veterinary Surgeons Act 1966.

The authors conclude that the study exposes shortfalls in our understanding of the global diversity and epidemiology of BoAHV-1, and they argue that expanding such collaborative studies to other countries, particularly in Asia and Africa, would broaden understanding of the virus and support its global control and potential eradication. Their case rests on three pillars: awareness of the virus’s economic impact, the relative ease of control through coordinated vaccination, and the trade implications of a virus that can spread through semen. For a pathogen that sits at the intersection of respiratory disease, fertility and international commerce, the message from this surveillance effort is that local testing programmes, when connected across borders and analysed with modern phylogenetic tools, can reveal patterns invisible to any single country working alone, and that the genetic story of BoAHV-1 is still being written in cattle populations far beyond the well-studied herds of Europe.

Subject of Research: Surveillance and phylogenetic analysis of bovine alphaherpesvirus 1 in bovine respiratory disease and semen samples in the UK and India

Article Title: Bovine alphaherpesvirus-1 in bovine respiratory disease and semen samples

Article References: Khatri, M., Chandrasekhar Reddy, R. V., Sarangi, L. N., Surendra, K. S. N. L., Ponnanna, N. M., Florea, L., Swinson, V., & Dastjerdi, A. (2026). Bovine alphaherpesvirus-1 in bovine respiratory disease and semen samples. Virology Journal. https://doi.org/10.1186/s12985-026-03289-w

Image Credits: AI Generated

DOI: 10.1186/s12985-026-03289-w

Keywords: BoAHV-1, infectious bovine rhinotracheitis, bovine respiratory disease complex, qPCR, UL44 genotyping, phylogenetics, semen screening, BRSV, PIV3, BCoV, APHA-Weybridge, WOAH twinning project