Landcare Research - Manaaki Whenua

Landcare-Research -Manaaki Whenua

Pest suppression (control) and sustaining Tb freedom

New Zealand currently spends over $100 million each year on controlling possums, rats, and other small mammal pests to eradicate bovine Tb and to reduce the impacts of these species on our native plants and animals. In spite of this expenditure, Tb remains widespread and native species are still in decline.

We aim to help managers identify what combination of operational approaches is likely to be most efficient and cost-effective in providing long-term control of multiple pests. We will do this by using models that will enable managers to predict the relative cost-effectiveness of alternative operational approaches within each of three major pest suppression systems (Tb eradication, local elimination of pests, and combined on-going control of possums and rats). Thus far, we have focussed very largely on Tb eradication.

New Zealand has achieved ‘official Tb freedom’ in livestock, with <0.2% of herds now infected annually. However, Tb is still present in possums, and TB-possum management still costs farmers c. $54M p.a. That cost could be reduced by regional eradication of TB from wildlife, but that faces two impediments: high initial costs, and reliance on 1080 poisoning, use of which will be increasingly constrained.

We aim to overcome these constraints to Tb eradication by:

  • targeting Tb control expenditure and greatly shortening its duration
  • developing better multi-source surveillance systems to identify Tb-free areas sensitively and cheaply
  • reducing reliance on 1080, by using other tools, including (as a back-up) the development of aerially deliverable Tb vaccine for possums and using that in conjunction with lethal control.

Long-term, the resulting gains in efficiency and cost-effectiveness could potentially halve the currently predicted 50+yr timeframe and $1billion cost estimated for national eradication of Tb. Such gains in efficiency could also more than double the total area in which native species are adequately protected.


  • Glen AS, Byrom AE, Pech RP, Cruz J, Schwab A, Sweetapple PJ, Yockney I, Nugent G, Coleman M, Whitford J 2012. Ecology of brushtail possums in a New Zealand dryland ecosystem. New Zealand Journal of Ecology 36(1): 29-37.
  • Nugent G, Whitford J, Yockney IJ, Cross ML 2012. Reduced spillover transmission of Mycobacterium bovis to feral pigs (Sus scofa) following population control of brushtail possums (Trichosurus vulpecula). Epidemiology and Infection 140(6): 1036-1047. <Go to ISI>://WOS:000304007700010
  • Barron M, Pech R, Whitford J, Yockney I, de Lisle G, Nugent G 2011. Longevity of Mycobacterium bovis in brushtail possum (Trichosurus vulpecula) carcasses, and contact rates between possums and carcasses. New Zealand veterinary journal 59(5): 209-17. <Go to ISI>://MEDLINE:21851297
  • Bosson M, Nugent G, Ramsey D, Caley P 2011. Combining livestock and wildlife surveillance data to access the likelihood of freedom from bovine tuberculosis in New Zealand. New Zealand Journal of Ecology 35(2): 195.
  • Fisher P, Nugent G, Morgan D, Warburton B, Cowan P, Duckworth J 2011. Possum Management Using Aerial 1080 – Not New, Definitely Improved. New Zealand Journal of Forestry 56(3): 5-8.
  • Nugent G, Morgan D, Clayton R, Warburton B 2011. Improving the efficacy of aerial poisoning of brushtail possums Trichosurus vulpecula through reduced fragmentation of bait. International journal of pest management 57(1): 51 - 59.
  • Nugent G, Yockney IJ, Whitford EJ 2011. Intraspecific transmission of mycobacterium bovis among penned feral pigs in New Zealand. Journal of wildlife diseases 47(2): 364-372.
  • Nugent G, Whitford J, Ramsey D 2011. [Abstract] Combining surveillance data from, and comparing the relative utility of wildlife sentinels for detecting bovine tuberculosis in New Zealand. New Zealand Journal of Ecology 35(2): 195.
  • Nugent G 2011. Maintenance, spillover and spillback transmission of bovine tuberculosis in multi-host wildlife complexes: A New Zealand case study. Veterinary Microbiology 151(1-2): 34-42. <Go to ISI>://WOS:000292352700006
  • O'Brien DJ, Schmitt SM, Rudolph BA, Nugent G 2011. Recent advances in the management of bovine tuberculosis in free-ranging wildlife. Veterinary Microbiology 151(1-2): 23-33. <Go to ISI>://WOS:000292352700005
  • Ryan TJ, Livingstone PG, Ramsey DSL, de Lisle GW, Nugent G, Collins DM, Buddle BM 2006. Advances in understanding disease epidemiology and implications for control and eradication of tuberculosis in livestock: The experience from New Zealand. Veterinary Microbiology 112(2-4): 211-.
  • Nugent G 2005. The role of wild deer in the epidemiology and management of bovine tuberculosis in New Zealand. Unpublished PhD thesis, Lincoln University, Lincoln, NewZealand. Lincoln, Lincoln University. - p.
  • Nugent G, Whitford J, Young N 2002/10. Use of released pigs as sentinels for Mycobacterium bovis. Journal of wildlife diseases 38(4): 665-677.
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