A second South Canterbury dairy farm belonging to the Van Leeuwen Dairy Group has tested positive for Mycoplasma bovis.
The Ministry for Primary Industries says the detection isn't unexpected, because of the close proximity to the first infected farm.
The Ministry says it's confident of containing the disease to the group's 16-farm block.
All of the group's farms remain in lock down, to stop the disease spreading to neighbouring animals.
Mycoplasma bovis does not infect humans and presents no food safety risk and there is no concern about consuming milk and milk products, the ministry said.
However, the bacterial disease can have serious effects on cattle, including udder infection, abortion, pneumonia and arthritis.
Other farmers in the area can be assured that the most likely way for a farm outside the Van Leeuwen Group to become infected would be the introduction of animals from the group. With all the farms in lock down, this cannot happen," MPI said today.
"Most other countries in the world, including countries in Europe, and the US, UK, and Canada live with Mycoplasma bovis in their cattle. This is a cattle disease and there are no food safety or human disease concerns associated with it".