Epidemiology and control of Mycobacterium bovis infection in brushtail possums (Trichosurus vulpecula), the primary wildlife host of bovine tuberculosis in New Zealand

Abstract

The introduced Australian brushtail possum (Trichosurus vulpecula) is a maintenance host for bovine tuberculosis (TB) in New Zealand and plays a central role in the TB problem in this country. The TB-possum problem emerged in the late 1960s, and intensive lethal control of possums is now used to reduce densities to low levels over 8 million ha of the country. This review summarises what is currently known about the pathogenesis and epidemiology of TB in possums, and how the disease responds to possum control. TB in possums is a highly lethal disease, with most possums likely to die within 6 months of becoming infected. The mechanisms of transmission between possums remain unclear, but appear to require some form of close contact or proximity. At large geographic scales, TB prevalence in possum populations is usually low (1–5%), but local prevalence can sometimes reach 60%. Intensive, systematic and uniform population control has been highly effective in breaking the TB cycle in possum populations, and where that control has been sustained for many years the prevalence of TB is now zero or near zero. Although some uncertainties remain, local eradication of TB from possums appears to be straightforward, given that TB managers now have the ability to reduce possum numbers to near zero levels and to maintain them at those levels for extended periods where required. We conclude that, although far from complete, the current understanding of TB-possum epidemiology, and the current management strategies and tactics, are sufficient to achieve local, regional, and even national disease eradication from possums in New Zealand.

KEY WORDS:

• Bovine tuberculosis
• disease control
• epidemiology
• maintenance host
• model
• Mycobacterium bovis
• New Zealand
• possum
• review
• Trichosurus vulpecula
• wildlife

Acknowledgements

This review was contracted by TBfree NZ (Project R10735-01), with co-funding from the Ministry of Business, Innovation and employment (Contact C09X0803). We thank the personal correspondents in this manuscript (Dr Paul Livingstone of TBfree NZ and Bruce Warburton of Landcare Research) for their information, and Dr Michelle Cooke for access to unpublished data. We also thank Frank Cross, Paul Livingstone and others for their input and comments on early drafts.

Notes

¹M.M. Cooke, Palmerston North, NZ

²P. Livingstone, TBfree New Zealand, Wellington, NZ.

³B. Warburton, Landcare Research, Lincoln, NZ.

*Non-peer-reviewed