Edinburgh Napier University

  To implement appropriate and effective disease control programs at national level, up-to-date and unbiased information on disease frequency is needed. The aim of this study was to estimate the prevalence of selected endemic infectious diseases in the population of dairy herds in Great Britain. Bulk milk tank (BMT) samples from 225 randomly selected dairy farms stratified by region and herd size were tested for antibodies against bovine viral diarrhoea virus (BVDV), bovine herpesvirus type 1 (BHV-1), Mycobacterium avium subspecies paratuberculosis (MAP), Leptospira hardjo , Salmonella spp., Coxiella burnetii , Fasciola hepatica , Neospora caninum , and Ostertagia ostertagi . Furthermore, the presence of BVDV, C. burnetii and Chlamydia-like organisms was determined by polymerase chain reaction (PCR). The apparent herd prevalence was estimated as a weighted proportion of positive herds. The true prevalence was calculated when a test was used with known test characteristics for the cut-off value used. Amongst unvaccinated herds, the true prevalence ofBMT antibodies against BVDV was estimated at 66% (95% Confidence 47 Interval, CI: 56-
77%), MAP 68% (95% CI: 59-77%), BHV-1 62% (95% CI: 52-73%), L. hardjo 47% (95% CI: 34-60%) and Salmonella spp. 48% (95% CI: 39-56%). The apparent prevalence of BMT antibodies against C. burnetii was 80% (95% CI: 75-85%), F. hepatica 55% (95% CI: 48- 62%), N. caninum 46% (95% CI: 38-54%), and O. ostertagi 95% (95% CI: 91-98%). BVDV, C. burnetii and Chlamydia-like antigens were detected in 5% (95% CI: 2-9%), 29% (95% CI:
21-36%) and 31% (95% CI: 24-38%) of herds, respectively. Our results show that dairy cows across GB are frequently exposed to the studied pathogens, which are endemic at high levels with some geographical variations. These prevalence estimates provide a much needed basis to assess whether nationwide control programs for the studied pathogens are justified by their potential economic, environmental and public health implications. Should surveillance and control programs be initiated, the estimates presented here are a baseline against which progress can be assessed.