Biosecurity, bovine viral diarrhoea virus (BVDv), and bovine herpesvirus-1 (BoHV-1): epidemiological investigations in Irish dairy herds

peer-reviewed
The fundamental basis of herd health planning and disease control is a science-based risk analysis. A disease risk analysis involves examining the probability of a disease occurring and the impact of that disease should it occur. Epidemiological investigations are required to provide the necessary data on biosecurity, disease prevalence, vaccination, and production losses associated with a particular infectious agent for the purposes of a comprehensive risk analysis. BVDv and BoHV-1 are highly contagious cattle viruses, exhibit a worldwide distribution and are listed as notifiable diseases by the OIE (Office International des Epizooties). A national eradication scheme is currently underway in Ireland for BVDv but no co-ordinated programme exists for the control or eradication of BoHV-1. Relatively little published data are available on the prevalence or production losses associated with BVDv and BoHV-1 infection in Ireland. Neither are data available relating to current biosecurity and vaccination practices on Irish dairy farms. The research programme outlined in this thesis aimed to provide relevant Irish stakeholders, such as AHI (Animal Health Ireland) and DAFM (Department of Agriculture, Food and the Marine), the necessary data to conduct an informed risk analysis on BVDv and BoHV-1. Results show that biosecurity practices, in general, were poorly implemented on dairy farms with lack of information cited as the primary cause. The concept of biosecurity was not well understood, a 20% discrepancy highlighted between self-declared and truly ‘closed’ herds. Additionally, inconsistencies in biosecurity practices and opinions across veterinarians, dairy advisors, and farmers were highlighted emphasising the need for improved communication amongst these stakeholders. Poor implementation of biosecurity is reflected in the prevalence of exposure to BVDv and BoHV-1 recorded in the current study. From a geographically representative population of 312 dairy herds, an appare