The Ministry for Primary Industries (MPI) says it will take two or three months of testing before the two South Canterbury farms hit by Mycoplasma bovis could be declared free of the cattle disease.
MPI, in its latest update, said the number of infected farms remained at two - both of them belonging to the Van Leeuwen Dairy Group (VLDG)
The ministry said it continued to build a picture of where the disease was present, to contain and eradicate it if possible.
MPI's response incident controller Eve Pleydell said laboratory teams worked at the weekend to continue testing the thousands of milk and blood samples from VLDG farms and neighbouring properties. To date 2,610 samples have been received.
"There have been no further confirmed positive test results and the situation remains at two positive affected farms, both in the VLDG," she said.
The first test results from seven of the VLDG farms have come back as negative for Mycoplasma bovis, she said.
"This is good news, but due to the difficulties of diagnosing this disease, two further rounds of testing will be required on these farms before they can be declared free of the disease," Pleydell said. "We expect testing to take two to three months."
Pleydell said MPI was working to establish whether the disease was occurring in other parts of the country.
The ministry is working with regional veterinary laboratories, Massey University and animal industry bodies to collect and analyse samples, including milk from cows that have mastitis, discard milk and routine bulk milk samples.
Key points
• 16 farms from the van Leeuwen group placed under Restricted Place Notices under the Biosecurity Act
• All 16 farms sampled and tested; 2 properties confirmed positive, 7 properties negative, results pending for remaining 7.
• There are 62 total surrounding, contiguous, properties. MPI is testing all that have cattle on them.
• On average, the testing process takes up to 7 days from taking the sample on-farm, to getting back to the farmer with the results.