The TBfree programme aims for TB freedom in possums by 2040.
TB freedom requires proof the disease has been removed, and while providing something isn't there is almost impossible, the proof of freedom model gives confidence that an area is free from TB.
TBfree takes the disease to such low levels in possums that it dies out. Then farm cattle and deer will no longer be at risk of contracting TB from wildlife.
Vector Risk Areas identify where it is believed TB exists in wildlife and as we travel down the road to TB freedom, targeted possum control is undertaken with ground and aerial operations.
Control operations reduce possum numbers to levels where TB can no longer be maintained. Once we are confident that TB is absent in possums, proof is required to declare areas TB-free.
The proof of freedom model considers possum control history, population density, TB testing history and survey results. The model guides decisions on what action to take next — continue possum control and surveillance activities, or stop. Once the proof of freedom model indicates 95% confidence that TB is absent, a panel of experts consider declaring an area free from TB.
When an area is declared free from TB, Vector Risk Areas are reclassified as Vector Free Areas, and pest control will cease for TB purposes.
We'll stay vigilant for signs of TB through ongoing testing of livestock on farms, through slaughter surveillance at meat processors, and with wildlife surveillance, as required.
Find out more: check your TMA on this website.
Controlling the possum population in NZ
Possums are the main source of bovine TB in New Zealand, and they're the focus of our pest control operations.
Managing and controlling our possum population is a major part of the TBfree programme, and a large part of the work we do at OSPRI. Our pest control work is designed to reduce the number of possums that could carry and spread TB to farmed livestock.
We know we can expect to eradicate TB from an area if we reduce the number of possums to a low and even level. This means about 1 possum per 10 hectares, for a period of at least 5 years. A low number like this means the disease:
- can't be maintained within the population
- will disappear from both possums and other wildlife in the area.
Pest control operations
Our pest control operations include ground and aerial control, and wildlife surveillance.
Ground and aerial control
Possum control is most often done through ground or aerial control operations.
- Our ground control operations use toxins and traps for possum control.
- Our aerial control operations are completed by dropping biodegradable 1080 into areas where ground control is difficult.
Wildlife surveys
We do wildlife surveys (especially on possums, pigs and ferrets) to find out if TB is still present in an area after we've completed our pest control operations. We do this by:
- trapping possums and other species that can spread TB, such as pigs and ferrets
- carrying out post-mortem examinations on these animals, and
- testing them for TB.
We do surveys in areas where we believe TB has been eradicated, and where we don’t expect to find any TB-infected possums or other wildlife.
TB management areas (TMAs)
We deliver our pest control operations through a framework of over 100 TMAs around the country. This framework helps us plan and contract our operations efficiently. Each TMA has an approximate planned target date for TB eradication.
Measuring our progress
We use the data gathered from our pest control operations to guide our future planning and measure our progress towards eradicating TB. We keep data on:
- the possum control history of an area
- possum population density
- the presence or absence of TB in possums and other wildlife in an area
- TB testing results from any cattle and deer herds in the vicinity.
We use the data to estimate the probability that the possum population in an area is free of TB. It guides our planning for any further pest control activities. For example, if there's a high probability of TB freedom in possums in an area:
- we'll replace our control operations with wildlife disease surveys, and we'll keep doing surveys until we can be sure that TB is no longer present
- we may decide to reduce TB testing in livestock and inspect carcasses at slaughter instead — this will provide the monitoring we need to detect any recurring or residual TB infection.