Eradicating bovine TB from Molesworth Station

Date 2017-11-30

An aerial possum control operation over the Molesworth Station was recently undertaken as part of OSPRI’s TBfree programme to eradicate bovine tuberculosis (TB) from wildlife and livestock across New Zealand. Recent informal surveys indicate by-kill of wild deer in the operation.

Molesworth Station has a long history with TB infection in its cattle herd and wildlife, dating back to the early 1960s. Significant progress has been made in reducing the numbers of infected animals through targeted pest control, TB skin and blood testing, with the removal of infected animals for slaughter.

Molesworth station is recorded as having the longest continuous infected herd status within New Zealand. Despite the success of the targeted programme, TB-infected wildlife remains present on the station and adjoining properties.

The Molesworth aerial operation covering 61,200 hectares of public and DOC-managed land began with a pre-feed operation on 12 October then a toxic bait application on 28 and 29 October. The operational area covered Wards Pass to the Acheron Accommodation House, then downstream of the Clarence River to the Spray Stream. Eight helicopters using GPS were used to complete the operation using standard bait sowing rates (pre-feed 1kg/ha and toxic bait 2kg/ha at an average cost of $25/ha for toxic application). GPS technology ensures accurate bait placement, and audits are completed to make sure that OSPRI’s high standards are met.

Significant public and community engagement has been undertaken throughout the operational planning and delivery phases. This started in late 2016 and has included national and regional consultation via the release of the 2017 TBfree consultation document, landowner/occupier and stakeholders meetings, as well as public consultation meetings.

The local NZDA branch and other private hunters were consulted throughout the implementation of this aerial operation. This resulted in NZDA Marlborough identifying an area for the application of deer repellent and OSPRI invested $20,000 towards this as part of the operation. Consulted parties were made aware that while OSPRI agreed to apply some of its limited resources to including deer repellent we would also accept financial contributions to enable its wider use.

OSPRI is continuing to invest in research towards cheaper and more effective use of deer repellent, and further operational trials will be carried out in 2018 to assess potential alternatives and their application in practice.

Although possums are the main source of wildlife infection, it is difficult and costly to directly detect TB in the possum population itself, because the disease often only occurs in small population clusters.

Because of this, most of our wildlife survey work looks for the presence or absence of TB in ‘spill-over’ hosts – mostly wild pigs and ferrets. These are particularly good indicators of TB in possums because they range widely and scavenge, making them prone to infection from eating TB-infected possum carcasses.

Based on this approach and earlier surveillance indicating a high density of TB-infected possums and livestock in the Molesworth area, OSPRI considered there was no need for further disease surveys ahead of this operation. The justification for possum control was compelling and also carried significant conservation benefits. A carcass survey for TB in deer would not have provided any useful further information to inform this most recent operation.

OSPRI recognises that there is always a risk of deer by-kill as a result of 1080 application for pest control and is committed to working with hunting groups to minimise the impacts on these populations through targeted use of deer repellent. This approach has been particularly successful in the central North Island in the high valued sika hunting areas.

In 2016 OSPRI launched the revised TB plan with the key milestones of TB freedom in livestock by 2026, TB freedom in possums by 2040 and biological eradication of TB from New Zealand by 2055.

 

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