Improving the diagnosis of bovine tuberculosis in farmed deer

Control of bovine tuberculosis (TB) caused by Mycobacterium bovis presents a considerable challenge as this bacterium infects a wide host range. M bovis infection in farmed and wild deer is important in many countries as the disease can be sustained in deer herds and infections in these animals have been implicated in the spread of M bovis to cattle (de Lisle and others 2001), O’Brien and others 2006) and people (Fanning and Edwards 1991). In Great Britain, control of the disease in deer is complicated as there is no routine statutory bovine TB testing programme and while in England, statutory powers require skin testing of M bovis-infected deer herds, testing is undertaken at the owner’s expense in order to determine freedom from disease. This requirement places additional pressure to ensure the accuracy of disease diagnosis. In a paper summarised on p 68 in this issue of Veterinary Record, Busch and others (2017) outline for the first time in England, the clearance of M bovis from a red deer herd following sustained skin testing over a two-year period. A strength in the study was the comparison of four different serological tests, leading to the identification of some skin test-negative, antibody-positive infected animals as well as preventing the slaughter of false positive, skin test reactors in the latter part of the study.