Farmers are being told to keep better records of livestock movements.
It follows another confirmed case of cattle disease Mycoplasma bovis, this time on an Ashburton farm.
The disease has been found on 14 farms, all but one are in the South Island.
Ministry for Primary Industries response incident controller David Yard said farmers have a poor record of compliance with the national livestock tracing scheme.
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Advertise with NZME.He said that's making for a lengthy search for the disease on other properties.
"It's proving extremely challenging for us to identify where all the animal movements are being made so we have to go and interview every farmer in detail to see if they can recall who they sold animals to and who they received."
Yard said public meetings will be held in Ashburton and Methven tomorrow.
He said screening between farms is a good idea.
"Because if they get it it is quite important they don't allow their animals to come in contact with their neighbours."
Milk sampling was carried out before Christmas, although the near 600 animals on the property showed no signs of illness.
Dairy NZ chief executive Tim Mackle said uncertainty of visible illness and fear of spreading is stressful for farmers.
"We really don't have the clearest picture right now of where this disease is and where it is not. Testing continues and we are well over I think 50,000 tests have been performed now."
