Testing for a disease that's so far seen around four thousand cows culled in New Zealand, will be rolled out nationwide.

Mycoplasma bovis milk testing is underway in Canterbury, Otago and Southland.

Now the Ministry for Primary Industries and its dairy industry partners will extend it into a national programme from next month.

MPI said while there is no indication the disease is present beyond the areas currently identified, checking for other possible regional clusters is essential to building a complete picture of the disease in New Zealand.

The latest case was confirmed in Ashburton earlier this week, bring the total number of infected properties to 14 - only one of those is in the North Island.