Research work vital to achieving a TB-free New Zealand
The primary wildlife source of bovine tuberculosis (TB) in New Zealand is the possum, with transmission of infection from possums to livestock regarded as a key barrier to eradicating TB from livestock.
‘Managing infectious diseases such as TB requires a comprehensive understanding of how the disease is transmitted from one individual to another and the rate at which it does so,’ says Dan Tompkins, Managing Invasives Portfolio Leader at Landcare Research.
As part of a larger project jointly funded by TBfree New Zealand and the Royal Society of New Zealand Marsden Fund, Landcare Research undertook a research project to improve how estimations are made about TB transmission rates among possums in the wild.
The study area located in the Orongorongo Valley area has a long history of TB in possums. The first incidence of TB in possums was first reported in the 1980’s and the area has never been declared free of the disease. TB Infected possums were most recently caught in 2012, along with tuberculous pigs in 2007. To date the area has not received possum control and it has long been a useful site for a number of studies of introduced wildlife including possums and TB.
As part of the project, 12 possums were infected and released in the study area. After six months, the 12 infected possums were caught and euthanaized. Other neighbouring possums in the area were caught and checked for signs of having been infected from the released possums. It was important to have a strain of TB which could be distinguished from the local wild TB strain to ensure any new infection could be attributed to the known number of infected possums.
The study has provided valuable information on the rate of possum to possum TB transmission in the wild, which helps determine the likelihood of TB persisting after long-term possum control at other sites.
‘Research projects such as this are critical to validate the rationale behind our work and improve how we deliver the TBfree programme’ says Matthew Hall, chief operating officer at OSPRI, which manages the TBfree programme.
Now that this study is complete, possum control is planned for the coming season to commence eradication of the existing natural infection in the possum population. The methods used and the choice of an existing infected study site mean that there has been no risk of causing any new TB infection or spread.
Landcare Research has more information on the research project here.