Marching towards a TB-free future

Date 2018-11-21

OSPRI Chairman Barry Harris says New Zealand farmers can be proud of the progress of the TB Plan towards eradicating the infectious livestock disease bovine tuberculosis.

Among the most important challenges facing New Zealand agriculture is managing and eradicating diseases that threaten our dairy and meat exports.

While Mycoplasma bovis has hogged the headlines recently, the progress of the TBfree programme to eradicate bovine tuberculosis has been quietly progressing as planned.

TB, caused by the similar-sounding Mycobacterium bovis, has been a problem for farmed livestock since they arrived in the 19th century.

It’s also a problem for human health because the disease is zoonotic: the infection can move from livestock to humans.

Because of its importance as a threat to agricultural products like meat and milk TB has been the focus of a highly successful eradication programme that has reduced infected livestock herds from 1700 30 years ago to just 32 this year.

The TBfree programme is designed to eradicate bovine tuberculosis from livestock by 2026, prove freedom from TB in possums by 2040 and prove biological freedom from TB throughout the country by 2055.

To achieve that – and the programme is right on target – the TB eradication plan takes a three-pronged approach: TB testing, controlling possums to prevent the spread of disease and stock movement control.

There has been remarkable progress in all three areas since the TB strategy was adopted in 2011.

TB livestock testing identifies infection in animals by scratching a taste of tuberculin into an animal’s skin and watching for a reaction. If the animal reacts with a swelling, a blood test can confirm it’s infected with TB.

All up, about 315 million TB tests were performed over the past year.

There’s less and less TB about so the risk of infection is lower and fewer tests are required. Farmers have needed 31,000 fewer herd TB tests this year as disease control area (DCA) boundaries tighten.

Shrinking DCAs indicate progress in the TBfree programme. In March, for instance, 2.3m hectares had their testing requirements changed – from once-a-year to once every two or three years, depending on risk. This year’s changes affected 1029 herds.

Changes to deer testing also occurred recently in preparation for the introduction of risk-based testing, which will bring TB eradication for the deer industry closer with added efficiency.

Controlling possums, as required by the National Pest Management Plan, takes the main transmitting species (vector) out of the TB cycle. That lessens the risk of disease passing between wildlife and farmed livestock but also stops the disease cycling in wildlife.

Well-established science tells us that by taking possum numbers to low levels (fewer than two possums per 10 hectares) and maintaining low numbers over a wide area for multiple years the disease dies out naturally.

That’s the second fundamental plank of the programme.

It’s a big job and it’s always done in consultation with the communities and landowners affected.

The programme carries out possum control operations and surveys wildlife over more than 4m hectares each year.

Those operations use the most appropriate method for the terrain: Most work, 90%, is achieved with ground control operations and the other 10% is covered by aerial 1080 drops in rugged, inaccessible country.

The TBfree programme’s control work has cleared TB-infected possums from 230,000 hectares of vector risk area in the past year, bringing the total area cleared since 2011 to more than 2m hectares.

The third plank of the TBfree programme is keeping tabs on the movement of animals around the country between farms and restricting any movements from areas where there is a disease risk so infected animals don’t pass disease to healthy animals.

Tracing and recording the movement of individual animals is managed by the NAIT traceability system and dovetails with the work of the TBfree programme. Both programmes are managed by OSPRI.

These three planks of TB eradication are supported by OSPRI’s investment in the highest-quality field and laboratory research from the most credible scientific organisations: Crown research institutes such as Manaaki Whenua Landcare Research and AgResearch and universities’ research outputs from their masters and doctorate study programmes.

Fundamental and applied research is done to support the control and eradication of TB in wildlife and livestock – animal health and disease analysis, testing methodologies and diagnostics and related activities that provide a scientific base for programme design.

The continued progress of TB eradication has been achieved on a budget of $60m, reduced from $80m two years ago. Funding reductions have been managed with a more efficient approach to testing and disease management and smarter pest control.

OSPRI’s programmes are working for farmers and the industries their work supports.

The company works hand-in-glove with the Government and the agricultural industry to create a prosperous and healthy future that fulfils the aspirations of all New Zealanders.

:: This article first published in Farmers Weekly 19 November 2018.

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