Abstract

The New Zealand government and agricultural industries recently jointly adopted the goal of nationally eradicating bovine tuberculosis (TB) from livestock and wildlife reservoirs by 2055. Only Australia has eradicated TB from a wildlife maintenance host. Elsewhere the disease is often self-sustaining in a variety of wildlife hosts, usually making eradication an intractable problem. The New Zealand strategy for eradicating TB from wildlife is based on quantitative assessment using a Bayesian “Proof of Freedom” framework. This is used to assess the probability that TB has been locally eradicated from a given area. Here we describe the framework (the concepts, methods and tools used to assess TB freedom and how they are being applied and updated). We then summarize recent decision theory research aimed at optimizing the balance between the risk of falsely declaring areas free and the risk of overspending on disease management when the disease is already locally extinct. We explore potential new approaches for further optimizing the allocation of management resources, especially for places where existing methods are impractical or expensive, including using livestock as sentinels. We also describe how the progressive roll-back of locally eradicated areas scales up operationally and quantitatively to achieve and confirm eradication success over the entire country. Lastly, we review the progress made since the framework was first formally adopted in 2011. We conclude that eradication of TB from New Zealand is feasible, and that we are well on the way to achieving this outcome.

Highlights

  • In 2016 the New Zealand government and agricultural industries jointly adopted the ambitious goal of nationally eradicating bovine tuberculosis (TB) from livestock and from all wildlife reservoirs by 2055 [1, 2]

  • Diagnostic testing and removal of test-positive animals, coupled with slaughterhouse carcass inspection and livestock movement control to prevent further outbreaks, has reduced TB levels in livestock in many developed countries [7], the disease has been difficult to fully eradicate, especially in countries where TB is independently cycling in wildlife reservoirs, such as badgers in Great Britain, wild boar and red deer in Spain, African buffalo and other species in South Africa, cervids in North America, and brushtail possums in New Zealand [8]

  • An exception is the successful eradication of TB from introduced water buffalo in Australia, where the “wildlife host” was a semi-domesticated or feral bovid with much the same TB epidemiological dynamics as cattle [9]

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Summary

INTRODUCTION

In 2016 the New Zealand government and agricultural industries jointly adopted the ambitious goal of nationally eradicating bovine tuberculosis (TB) from livestock and from all wildlife reservoirs by 2055 [1, 2]. By the mid-1900s it had spread into wildlife, and the disease became widely established in a highly susceptible and ubiquitous maintenance host, the introduced brushtail possum (Trichosurus vulpecula) [4], from which it often spills over to a number of other wildlife hosts, including feral pigs and wild deer [5] and feral ferrets [6]

New Zealand Wildlife TB Eradication
MANAGEMENT OF TB IN NEW ZEALAND
The TB Freedom Concept
Theoretical Prediction of TB Freedom Based on Control Effectiveness
Combining Surveillance and Final Control
Balancing Control and Surveillance Effort and Optimizing the Stopping Rule
Livestock as Sentinels
Scaling Up From VCZs to National Eradication
PROGRESS TOWARD ERADICATION
DISCUSSION
Findings
Stopping rule Surveillance TB TB possum VCZ VRA
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