Broad-scale possum and ferret correlates of macroscopic Mycobacterium bovis infection in feral ferret populations

Aims. To examine the relationships between the prevalence of macroscopic Mycobacterium bovis infection (bovine tuberculosis) in feral ferrets (Mustela furo), the abundance of ferrets, and the abundance of brushtail possums (Trichosurus vulpecula). Methods. Data on the prevalence of macroscopic M. bovis infection in ferrets, abundance of ferrets, and abundance of possums were analysed from 12 comparable independent broad-scale surveys. Results. The prevalence of macroscopic M. bovis infection in ferrets was positively correlated with possum abundance but unrelated to ferret abundance, suggesting that possums are an important source of M. bovis infection in ferrets. The lack of any positive relationship between the prevalence of M. bovis infection in ferrets and ferret abundance does not support the hypothesis that per capita transmission rates, and therefore disease prevalence, should be higher at higher ferret abundance. Conclusion. The results support the hypothesis that tuberculous possums are the major underlying source of M. bovis infection for feral ferrets in New Zealand.