Distribution, Prevalence, and Epidemiology of Bovine Tuberculosis in Brushtail Possums, Trichosurus-Vulpecula, in the Hohonu Range, New-Zealand

Abstract

Over a 12-month period, 1467 brushtail possums were trapped and then killed or were poisoned along sampling lines on pasture-forest margins and in nearby forest. An additional 334 possums were shot on adjacent farm land. All possums were necropsied, and 141 had macroscopic lesions typical of bovine tuberculosis. Infected possums occurred most commonly in small foci of 2-5 individuals along pasture-forest margins; the furthest from pasture that an infected animal was taken was 4050 m. Lesions occurred in possums of all ages in both sexes, but disease prevalence was highest in immature males and during autumn and winter. Infected possums bred as successfully as non-infected individuals, but were of lighter body weight. Macroscopic lesions occurred in a wide range of visceral and lymph node sites. Lesions were most common in the lungs and axillary nodes, and occasionally formed open sinuses from which infected possums could shed M. bovis readily, and thus were likely to be highly infective. Evidence suggested that disease transmission occurs most frequently on pasture-forest margins, where possum numbers are greatest and possum and cattle mix most freely.