Papers Papers

A retrospective cohort study was conducted to determine the risk of bovine tuberculosis (TB) among animals sold out from herds that were free to trade animals during the year 2005 according to their bovine TB testing history during the year 2005. The present study sample comprised of 338,960 animals, of which 124,360 animals were sold out from herds that were restricted from trading at some stage during 2005 (bovine TB ‘exposed’) and 214,600 animals that were sold from herds which did not have their trading status withdrawn in 2005 (bovine TB ‘non-exposed’). The overall risk of a diagnosis of bovine TB during the two-year period after the animals were sold out was 0.69 per cent. The odds of bovine TB were 1.91 higher for animals sold out from bovine TB ‘exposed ’ herds compared with animals sold out from bovine TB ‘non-exposed ’ herds (OR 95 per cent CI: 1.76 to 2.07, P<0.0001). Ten per cent of animals identified during field surveillance with bovine TB did so less than two months after being sold out in 2005, and similarly, 10 per cent of the animals classified as bovine TB positive by finding a bovine TB lesion at slaughter did so within 25 days (or less) of being sold out in 2005. Mycobacterium bovis is the agent that causes bovine tuberculosis (TB), a chronic infectious-contagious disease of cattle. Although bovine TB was once distributed worldwide, control programmes have success-fully eradicated the disease from domesticated animals in many devel-oped countries. In countries such as the Republic of Ireland, where the disease persists despite bovine TB control programmes that are in place, the later stage pathology of the disease is rarely observed at postmortem meat inspection due to the early and constant removal of infected animals. Thus, animals infected with M bovis in Ireland present most commonly as outwardly healthy, showing an immuno-logical response to the tuberculin test (Collins 2006). The Irish national bovine TB eradication programme is a com-prehensive disease surveillance strategy and consists of compulsory annual farm-based tuberculin skin testing of all cattle using the Singl