Bovine tuberculosis (Tb) is the most important disease of livestock in New
Zealand, and it puts at risk the nation's trade in dairy, beef and venison
products. Elimination of the disease from livestock is based on a herd test
and slaughter programme and carcass inspection at abbatoirs. However, this
programme has not been as successful as expected, because the disease also
occurs in wild or feral animals acting as vectors of the disease to livest
ock. Brushtail possums are the major wildlife vector and self-sustaining ma
intenance host of Tb, and play a role analogous to that of the badger in Gr
eat Britain. In contrast, some deer species and ferrets may act as vectors
of the disease, but their role in transmitting Tb to livestock is unclear.
Hedgehogs, pigs, cats, sheep and goats are now considered to be amplifier h
osts, and spread the disease to other species only when inspected or their
carcasses scavenged. In the absence of infected possum populations, these s
pecies do not appear to be capable of maintaining the infection in their ow
n populations and are not thought to be involved in the maintenance of Tb i
n livestock. Tuberculosis has also been recorded from stoats, hares, and a
rabbit, but the level of infection recorded in their populations indicates
these species are unlikely to spread the disease to other animals and hence
are not involved in the transmission of Tb to livestock. (C) 2001 Harcourt
Publishers Ltd.