In New Zealand, we embarked on 'test and slaughter' measures for TB during the mid-to-late 20th century. By 1970 all cattle herds were undergoing:
By the 1980s, we had eradicated TB from cattle populations across large areas of the country. This included Northland, Taranaki and mid-Canterbury. However, this was not the case in other regions, like:
In these areas, the test and slaughter approach failed. This suggested something else was infecting livestock.
In 1969, vets found proof that the invasive brush-tail possum was carrying bovine TB — and passing it to farmed cattle and deer. But we don't know how long possums have been carrying TB. Evidence shows that the disease crossed between cattle and possums in as few as 20 separate incidents across the country.
Possums were the perfect host for TB. They had no evolutionary exposure or resistance to the disease. And, with abundant food and no natural predators, the population in NZ was far higher than in their native Australia.
By the 1970s, possum-related TB was a major cause of livestock infection in heavily forested areas, like the West Coast, Wairarapa and the central North Island.
The government started investing in possum control for forest conservation purposes in the 1970s. Resources were allocated to areas with major TB problems. This led to a sharp decline in livestock infection levels throughout the late 1970s.
But, in 1978 government funding for possum control was withdrawn due to:
The problem of inadequate funding was made worse by an ad hoc and fragmented approach to TB control in general.
The Ministry of Agriculture ran a livestock 'test and slaughter' programme, funded by industry levies. This proved futile against a growing wave of TB infection by possums. Possum control was left to a network of locally funded pest destruction boards, though they had some support from the national Agricultural Pest Destruction Council (APDC).
The APDC was constrained by inadequate local funding and conflicting pest management priorities. In 1989, both the APDC and local pest boards were dissolved in a major reform of local authorities. New regional councils inherited their staff, infrastructure and functions, despite having no clear or legislated responsibilities for pest management.
We saw a gradual and then exponential increase in TB in livestock during the 1980s. This peaked in 1994, with over 1700 cattle and deer herds infected with TB. This represented a herd infection prevalence of more than 2%, far higher than in most other developed countries. It created a potential risk to our New Zealand beef, dairy and venison export industries.
During the 1980s, the government delegated national TB control policy and decision-making to an industry-led advisory committee. The committee became an incorporated society — the Animal Health Board (AHB) — in 1993. Its mission statement was 'to eradicate bovine tuberculosis from New Zealand'. Membership of the AHB came from:
Working through the Biosecurity Act of 1993, the AHB proposed a National Pest Management Strategy (NPMS) for bovine TB. This came into effect in 1998.
The AHB assumed management and legal control of the TB programme and operations under the Biosecurity Act, and:
It also formalised relationships with:
Based on historical experience and funding expectations, NPMS’ initial objectives were to:
The number of infected herds fell to 666 by June 2000. But, we saw more TB infection in wildlife, particularly:
In 2001, recognition of this problem led to funding increases for TB control, from both the government and industry.
These increases foreshadowed a major review of the NPMS. AHB proposed the review in 2001, and it was completed through a strategy amendment in 2004.
The amendment introduced what was then considered a challenging goal. This was 'to reduce the national herd infection rate to no more than 0.2% by 2013'. Achieving this goal would mean New Zealand met the international standard for 'official freedom' from TB in cattle and deer herds.
The technological and managerial improvements in TB control were what led us to believe we could achieve this goal.
The introduction of the Residual Trap Catch Index (RTCI) gave us a reliable and affordable way to:
It also provided the basis for performance-based, commercially contracted possum control. Within a few years, possum control shifted from being a local government service into a commercial activity.
Further research led to improvements in the cost-effectiveness and reliability of possum control. This included:
The AHB inherited a state monopoly in the area of TB control, which it broke by developing in-house management systems. This meant field operations could be offered for commercial tender across the regions. As a result, the private veterinary sector started competing for this work.
Other technical and managerial improvements included:
Progress towards the 0.2% infected herd prevalence target soon exceeded expectations. This was due to:
The geographic spread of infected wildlife populations was also curbed, and we eradicated TB from wildlife in some areas. By June 2007 we had:
This led to a re-think of the feasibility of total eradication of TB from both herds and wildlife. Eradication is the obvious and ideal end point for any disease management programme, but we had always considered eradication too difficult to be realistic.
We had achieved eradication of TB from wildlife in places like Kaipara South Head and Banks Peninsula. Could we achieve it in much larger areas of heavily forested, rugged possum habitats too?
Improved performance in large scale aerial-baiting operations for possum control emerged as the possible answer to this question. In 2004 and 2005, aerial control operations were completed in:
This reduced possum density to about 1 animal per 100 hectares, over areas of up to 50,000 hectares. If we could maintain these low numbers, we could expect to eradicate the disease.
In late 2007, the AHB proposed a range of options for future control and eradication of TB in New Zealand. This happened in the lead-up to a 5-year review of the NPMS, due by 2009. AHB member organisations and the government agreed to put forward a preferred option to amend the NPMS to provide for operational and strategic proof of the eradication concept. The formal strategy review and amendment process was completed by mid-2011.
The agreed objectives for 2011 to 2026 were:
Between 2011 and 2016, we:
This work laid the foundations for the next phase of the eradication programme.
Under the Biosecurity Act, a review of the national TB plan needed to be done by 1 July 2016. As part of this, the government and industry partners had to define and agree on a sustainable funding arrangement. The review began in 2015 by consulting with farmers, local communities, and other stakeholders on the proposed changes.
The new TB plan was approved by government in June 2016. It gives us a nationally coordinated and long-term approach to eradicating TB from New Zealand.
The key objectives of the plan are to achieve: