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BOVINE tuberculosis (bTB) is a zoonotic infection caused by Mycobacterium bovis that continues to be a major economic problem for farming in Great Britain (GB). The incidence of bTB in cattle has risen steadily since the late 1980s despite the widespread use of the tuberculin skin-test-based test and slaughter-control strategy. Although living in a wildlife reservoir, the European badger (Meles meles), has been implicated in disease maintenance and transmission to cattle. Cattle-to-cattle transmission also contributes to the maintenance of this disease in the GB cattle population (Goodchild and Clifton-Hadley 2001). A better understanding of factors facilitating transmission between cattle is therefore desirable. We present data of an experiment of cattle-to-cattle transmission using naturally infected donor animals (skin-test reactors) with the aim of providing novel insights into disease transmission. In addition, we have assessed the suitability of this model for testing bTB vaccine candidates.
Tuberculin skin-test-positive cattle (n=39), termed donors, were sourced from farms in England and Wales with previously confirmed bTB outbreaks. The uninfected animals (n=60), termed sentinels, were recruited from TB-free farms in regions of England known to have low incidence of bTB. Sentinel cattle were recruited at five weeks of age and housed in isolation at Veterinary Laboratory Agency (VLA)-Weybridge prior to introduction to the donors. This study was initially designed to determine vaccine efficacies under natural transmission conditions, therefore, 40 of these sentinels were vaccinated subcutaneously at four to six weeks of age with 2–3×106 colony forming unit (CFU) of Bacillus Calmette-Guérin (BCG) Danish (Staten Serum Institute, Copenhagen) which equates to five standard human doses. Twenty of the BCG vaccinates were subsequently boosted with a recombinant adenovirus-expressing mycobacterial antigen 85A (Vordermeier and others 2001, 2006) at …