New Zealand has ordered the culling of 126,000 cattle in an attempt to eradicate the painful Mycoplasma bovis disease, which causes udder infections, pneumonia and arthritis.
The decision was taken to "protect the base of our economy - the farming sector," Prime Minister Jacinda Ardern said.
"This is a tough call - no one ever wants to see mass culls. But the alternative is the spread of the disease across our national herd."
Mycoplasma bovis does not affect milk and meat for human consumption, and most governments are content to control outbreaks.
However, Ms Ardern said New Zealand - which relies heavily on livestock farming for its export earnings - would aim to eradicate the disease completely.
"We do believe we are taking it on at a point that it is possible to eradicate and more than 99 percent of farms don't have it and we want to protect them from having it."
The phased eradication, to take place over two years at a cost of NZ$886 million, represents only a fraction of New Zealand stock, with some 4.2 million cattle slaughtered annually.
Mycoplasma bovis has been found on about 40 farms so far but the government believes 192 properties will eventually be involved in the cull.
Already, 26,000 cattle have been destroyed in the 10 months since the disease was first recorded in New Zealand.
Agriculture Minister Damien O'Connor said it was believed the outbreak came from one source and that expert advice indicated it was possible to contain and eradicate it.
However, many healthy cattle will also be killed in the cull.
"The majority of animals that we do cull in New Zealand are all healthy. This is a necessary, unfortunate part of not having yet a test that clearly identifies the individual animals," he said.
