Infectious Bovine Rhinotracheitis (IBR)
Bovine Herpesvirus 1 (BoHV-1): A Comprehensive Guide
Introduction
Bovine Herpesvirus 1 (BoHV-1), an alphaherpesvirus, is a major cattle pathogen causing infectious bovine rhinotracheitis (IBR) and other diseases. This virus has a significant impact on cattle health and international trade, necessitating comprehensive management strategies in veterinary practice.
History and Epidemiology
BoHV-1, initially identified during outbreaks in the US during the 1950s, has since gained worldwide distribution. The prevalence varies, with herd level prevalences up to 85% in regions with established cattle enterprises. The disease's impact within herds is unpredictable, making vigilant monitoring crucial.
Clinical Manifestations
BoHV-1 infection ranges from severe and fatal to mild and subclinical. Common symptoms include respiratory distress, decreased milk production, and, in some cases, abortions. The variability of these infections is influenced by viral, host, and environmental factors. Subclinical infections are widespread, and the severity of the disease is often exacerbated by secondary bacterial infections.
Transmission and Survival
Transmission primarily occurs through direct contact with infected cattle or re-excreted latent virus. The virus can survive in the environment under specific conditions, including low temperatures and high humidity, posing a risk of transmission between farms.
Pathogenesis
BoHV-1 replicates in the upper respiratory tract, leading to clinical symptoms like pyrexia and nasal discharge. The virus can also enter the central nervous system (CNS) without necessarily causing clinical signs of nervous disease. In reproductive tract infections, BoHV-1 is introduced through natural mating or artificial insemination and does not arise from viraemia from respiratory infections.
Immune Response and Latency
An efficient immune response, involving interferon production and both humoral and cellular immunity, contributes to recovery. However, every bovine animal with BoHV-1 antibodies has a lifelong latent infection, posing a continuous risk. Reactivation from latency can occur under stress or corticosteroid induction.
Diagnostic Approaches
Diagnosis often requires laboratory confirmation in addition to clinical observations. Virus detection is highest during the early stages of infection, and serology is an essential tool for diagnosis and control. Understanding the vaccinal history of animals is crucial in interpreting serological tests.
Vaccination Strategies
A range of vaccines, including marker vaccines, is available for BoHV-1. Marker vaccines allow differentiation between infected and vaccinated animals, essential in control and eradication programs. Vaccines are effective in preventing clinical disease and reducing virus spread but do not completely prevent infection.
Control and Eradication
Control and eradication of BoHV-1 are feasible with the availability of excellent diagnostic tools, understanding of the virus biology, and effective IBR marker vaccines. Several European countries have initiated control and eradication programs, highlighting the potential for long-term eradication.
Conclusion:
For veterinary professionals, managing BoHV-1 requires a multifaceted approach involving accurate diagnosis, effective vaccination, and herd management strategies. Understanding the disease's variability, transmission risks, and the role of stress in reactivation is vital. Continuous research and application of these insights are essential in managing BoHV-1 effectively and protecting cattle health and productivity.
This article aims to provide veterinary professionals with a comprehensive understanding of BoHV-1, emphasizing the importance of a strategic approach in managing this significant cattle pathogen.
References
Muylkens, B. "Bovine Herpesvirus 1 Infection and Infectious Bovine Rhinotracheitis.” Vet. Res. 38 (2007), 181-209.
Nettleton, P. F. "Update on Infectious Bovine Rhinotracheitis”. In Practice. June (2017). Volume 39, 255-272.
