Dairy Farming in New Zealand - Pest and Diseases

Pest and Diseases

Bovine tuberculosis is currently (2012) endemic in possums across approximately 38 per cent of New Zealand (known as ‘vector risk areas’). In these areas, nearly 70 per cent of new herd infections can be traced back to possums or ferrets. The Biosecurity Act 1993, which established a National Pest Management Strategy, is the legislation behind control of the disease in New Zealand. The Animal Health Board (AHB) operates a nationwide programme of cattle testing and possum control with the goal of eradicating M. bovis from wild vector species across 2.5 million hectares – or one quarter – of New Zealand’s at-risk areas by 2026 and, eventually, eradicating the disease entirely.

Possums are not native to New Zealand, and are considered both an agricultural and a conservation pest. They are controlled through a combination of trapping, ground-baiting and, where other methods are impractical, aerial treament with 1080 poison.

From 1979–1984, possum control was stopped due to lack of funding. In spite of regular and frequent TB testing of cattle herds, the number of infected herds snowballed and continued to increase until 1994. The area of New Zealand where there were TB wild animals expanded from about 10 to 40 per cent.

That possums are such effective transmitters of TB appears to be facilitated by their behaviour once they succumb to the disease. Terminally ill TB possums will show increasingly erratic behaviour, such as venturing out during the daytime to get enough food to eat, and seeking out buildings in which to keep warm. As a consequence they may wander on to paddocks, where they naturally attract the attention of inquisitive cattle and deer. This behaviour has been captured on video.