New Zealand plans to slaughter more than 150,000 cows to eradicate a disease-causing bacteria that is threatening cattle in a nation which has long avoided mass outbreaks due to its isolation.

Jacinda Ardern, the prime minister, said she empathised with farmers facing the “pain” of losing their cows but warned that failing to act could threaten the country’s entire herd. New Zealand has 10 million cows, slightly more than double its human population.

“Standing back and allowing the disease to spread would simply create more anxiety for all farmers," Ms Ardern said.

The move follows the discovery last July of a case of Mycoplasma bovis, a bacteria that can cause mastitis, pneumonia, arthritis and other diseases. It is not as serious as foot-and-mouth disease, which resulted in the slaughter of more than six million animals in Britain in 2001.

New Zealand was previously the only country, aside from Norway, which was believed to be free of Mycoplasma bovis and, if the cull is successful, would be the first to wipe out the bacteria.