A property in wider Canterbury was confirmed following a detected result from September screening.
"We are working closely with all affected farmers, their staff and whanau to ensure things run as smoothly as possible, and that they are well supported," he said.
"It's important to note this is not an outbreak – the M.bovis programme is actively looking for those final pockets of infected properties and fully expected to find more over spring," he said.
"It's a time we have more samples to test, animals are under stress from calving and we have 2018 heifers entering the milking platform for the first time."
It was also not believed to be widespread.
"No additional farms in Mid Canterbury, other than those three dairies originally detected in August, were detected in September or October bulk tank milk screening, giving us confidence this is an isolated cluster connected by animal movements."
Programme staff would continue to trace the movements of cattle until all those of interest were investigated. They were helped by good Nait records.
"Incomplete Nait records make tracing infected cattle a difficult job and our surveillance tools like our bulk tank milk screening programme and beef sector surveillance have been developed to not only help find any remaining infection faster, but to give us confidence long-term that New Zealand is free from the disease."
The Ashburton district has had 34 cleared confirmed properties with more than $44 million paid across 307 claims from the district, but there were still 24 financial claims being processed relating to Ashburton farms; some farms with multiple claims.
Mr Anderson said 13 were being assessed. Two claims are loss of milk income being paid on a monthly basis and nine claims involve three farms which are subject to ongoing legal action/negotiation.
