The use of deer, pigs, and ferrets as indicator species for detecting Tb

The pest management strategy for bovine tuberculosis (Tb) in New Zealand aims to achieve official freedom from Tb before 2012 and to eradicate the disease from livestock and wildlife. On farmland, regularly tested cattle and deer usually provide adequate surveillance of Tb presence in sympatric wildlife, but there are many other areas where livestock are absent or their densities too low to be useful. For these areas, Tb prevalence in the wildlife hosts must be surveyed directly but brushtail possums (Trichosurus vulpecula), the main host, make poor sentinels (indicators) for identifying Tb presence or absence. Consequently, persistent Tb can go undetected for long periods. The trials reported here assess the feasibility and practicality of alternative techniques for Tb surveillance in wildlife – the use of ‘spillover’ hosts as sentinels for detecting Tb presence or helping quantify its likely absence. Spillover hosts become infected mainly through interaction with other species. This paper will discuss the use of these species to detect both the presence and the spread of bovine Tb in wildlife in the central North Island of New Zealand.