TB PREVALENCE IN WESTLAND
tuberculosis(Tb)is a world wide disease caused by the bacteria Mycobacterium
bovis. Included in the same complex of bacteria is M. tuberculosis
(human Tb). Bovine tuberculosis is widespread throughout temperate areas of the
world with cattle being its natural host.
In cattle Tb is a debilitating, chronic, often fatal disease, readily
transmitted to other cattle. Humans can become infected by drinking
un-pasteurised milk or through direct contact with animals or carcasses. Meat
inspection at abattoirs and pasteurising of milk are effective measures of
limiting human infection but M. bovis infection still causes 100,000 -
200,000 human deaths worldwide annually. The possum is considered the primary
wildlife reservoir of Tb for farmed cattle in NZ, and continuing transmission of
Tb from tuberculosis possums to livestock is the greatest single barrier to its
eradication from NZ livestock.
In New Zealand Tb was first recorded in free ranging possums in 1967 in the
Buller region, but by the early 1970s infected possums were recorded in widely
dispersed areas such as Inangahua, Grey Valley, Wairarapa, Nth Canterbury,Taupo
and Otago. In each instance infected possums coexisted with tuberculosis cattle.
In 1978 similar possum related disease outbreaks were identified in farmed deer,
and the transmission of Tb from them to coexisting possum populations has been
documented several times.
Tb infected possum populations now occupy about 23% of New Zealand and this
figure appears to be increasing as juvenile infected possums and deer can travel
reasonably large distances.
Photos showing possums with TB lesions
Map showing main TB areas in NZ