Gwyn said MPI was working with the farmer to contain the disease and treat animals showing symptoms.
Legal restrictions were in place to stop any movement of stock from the property while the scale of infection was determined. MPI was appreciative of the farmer's support.
The ministry was advised of sick cattle at the property last Monday and the disease was confirmed by the ministry's animal health laboratory late on Saturday.
Fourteen cows tested positive and about 150 cows had clinical signs that indicated they might be affected.
MPI was now tracing movements of animals on and off the property to ascertain if other properties were at risk. It did not know at this stage when or how the disease entered New Zealand.
Farmers were advised to contact their vet if stock showed unusual levels of mastitis or abortions, or presented with arthritis or pneumonia. The disease had no effect on other types of animals.
When contacted, Federated Farmers dairy industry group chairman Chris Lewis said he hoped the outbreak could be contained on the property and eradicated.
From Federated Farmers' perspective, the number one priority was the animal and human welfare around the issue.
The second priority was working with the likes of MPI, vets, dairy companies and DairyNZ to find answers to ''lots of questions'' around the outbreak, Lewis said.