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It is too soon to say whether the latest cattle confirmed with Mycoplasma bovis will be culled.
The Ministry for Primary Industries said it would ''not be making hasty decisions'' on such matters, when asked by Central Rural Life.
Last week, the ministry reported the most recent cases of the bacterial cattle disease were found near Hastings and Winton, and another was ''strongly suspected'' at Ashburton.
The Hastings and Ashburton cases were identified though the ministry's tracing programme and the Winton properties through the dairy industry's milk-testing programme.
The Hastings and Southland farms were under quarantine lockdown and the Ashburton property had voluntary animal and goods movement controls in place until its disease status was confirmed.
''Our investigators are building a picture of stock movements on to and off these farms, just as they did in Waimate,'' Mr Gwyn said.
The outbreak began in July on dairy farms owned by the Van Leeuwen Dairy Group near Waimate. There were now 13 infected properties, all thought to have had contact with van Leeuwen livestock.
Cows on the infected van Leeuwen farms were being culled. More than 3500 had been slaughtered and about 1500 more were due to be before Christmas.
''We're still analysing what these latest positive properties mean for the wider response,'' Mr Gwyn said.
''We're dealing with a lot of uncertainty.''
The ministry's Oamaru field headquarters would remain in place through the Christmas and New Year period. Staff would take leave on the statutory holidays but were available on call, Mr Gwyn said.