In August the country was declared free of M bovis. File pic Photo: 123RF
A second Selwyn farm is infected with cattle disease mycoplasma bovis.
It's next door to the other infected farm and has been under movement restrictions for several weeks.
The two farms will be cleared of cattle and disinfected by early next year.
First detected in New Zealand in 2017, the disease causes animal welfare and productivity issues such as mastitis (udder infection), pneumonia, arthritis and ill-thrift in calves.
An update from the Ministry for Primary Industries said it was not known how the second farm became infected but it was working with the farmer to mitigate any risk of the disease spreading.
"This will likely see an increase in the number of farms under movement restrictions while we mitigate the risk of disease spread.
"Our team will be in touch with any farms affected and experience tells us that in most cases these restrictions will be lifted quickly."
MPI said finding further infection in the tail end of an outbreak was not uncommon and it has been previously signalled more properties could be found.
"It is possible more properties will be confirmed infected in the coming months."
In August, New Zealand reached no known cases, after the last property was cleared of cattle and declared disease-free.