Bovine TB in New Zealand - journey from epidemic towards eradication

Abstract

Bovine tuberculosis (TB), caused by Mycobacterium bovis, has a unique and complex ecology in New Zealand. Unlike elsewhere in the world, the disease is maintained in Australian brushtail possums (Trichosurus vulpecula) and so they are considered a vector for disease transmission in New Zealand. Possums were initially introduced to the country in the 1800's to establish a fur industry but later becoming a recognized pest to native New Zealand flora and fauna. The TB programme in New Zealand (TBFree NZ Ltd) is managed by a not-for-profit limited company partnership between primary industries and government (OSPRI - Operational Solutions for Primary Industries) that uses the basic tenets of disease management, movement control and vector control to eliminate TB in farmed cattle and deer. Evidence of resounding success in the TB control programme resulted in the 2016 decision to pursue full biological eradication of disease from the country by 2055, with the interim objectives of TB freedom in livestock herds by 2026 and TB freedom in possums by 2040. The programme has progressed from an all-time high of 1698 infected herds in 1995 to the lowest recorded point prevalence of 18 infected herds in May 2022. Enhancements that have contributed to the success of the programme include testing with gamma-interferon release assay (Bovigam™) of animals in infected herds that are negative to the skin test (parallel interpretation), culturing pooled lymph nodes from animals without visible lesions, increased testing of herds post-clearance and introduction of post-movement testing of high-risk animals.

Keywords: Bovine tuberculosis; Brushtail possum; Eradication; New Zealand; OSPRI.

Fig. 1

Infected herds in New Zealand from the peak in 1995 to the lowest recorded level in May 2022 (orange squares beef herds, green dots dairy herds and red triangles deer herds)