All detections to date had links to the original infected properties via animal movements and had been caused by close animal contact.
It was encouraging no adjacent properties had as yet been identified as infected, despite intensive testing.
"We have no evidence of any means of disease spread other than close animal contact, at this stage. This includes the disease having jumped fences, which our scientists and vets tell us is highly unlikely to occur," he said.
The two latest VLDG properties were already under restricted place notices, while the North Canterbury lifestyle block received a small number of calves from the third infected farm confirmed last week.
MPI was continuing with its policy of not naming the affected properties if the owners did not want that.
However, it understood community concern about the disease and was "strongly encouraging" farmers under controls or investigation to talk to their neighbours, customers and suppliers.
North Otago farmer Julian Price expressed concerns about MPI's response, saying he believed it should be "casting the net wider".
Last week, a farm in the Oamaru area was added to the list of infected properties, having received animals from an infected VLDG farm, before the disease was detected.
Mr Price, who farms near Maheno, said he received a phone call from an upset neighbour last Friday morning "like a bolt from the blue".
The neighbour's stock had been next to animals which he subsequently found out were to be tested for the disease and he was giving Mr Price "a heads-up" so he knew not to put his own animals next to them. That was the first time that Mr Price knew where the infected property was. He stressed the animals on the boundary were not from a known infected property.
Mr Price realised the same mob was now next to his heifers. He immediately put another electric wire around the inside of the boundary fence to prevent close contact.
He had since talked to the owner of those stock, who was confident there was no risk his stock were infected.
"I don't share that confidence. I see a risk, however small," Mr Price said.
He and his neighbour agreed on a "buffer zone" which, because of the nature of terrain, would be on Mr Price's side.
"Because things have been kept secret, I didn't know we needed to talk," he said.
Mr Price did not expect MPI to publicly announce the name of the "unfortunate" owner of the infected property - "but they could be driving up driveways and quietly telling people "this is the story."
"They need to be casting the net wider. There's absolutely no blame or shame in having the disease on your farm. You're just a victim of circumstances," he said.
But some guidance was needed from MPI "as to where it is and where to from here".
"I want to take all the precautions I can, but if you don't know, you don't know to take precautions.
"To my mind, it should almost be a good practice run for other exotic diseases and they've not covered themselves in glory," he said.
Federated Farmers biosecurity spokesman Guy Wigley said it was "important to keep things in perspective" and not increase anxiety among farmers.
"The reality is it exists in most countries and they manage it just fine, with trade unaffected. We know the frustration out there, but this is a complex bacterial infection which we have never encountered before here in New Zealand," Mr Wigley said.
MPI was "throwing significant resources" at containing the disease and was positive it could be eradicated, he said.
Federated Farmers had heard of farmers who were bothered by MPI's inability to identify affected properties, because of the Privacy Act.
"Apart from the obligations under the law, this is not the time to incriminate other farmers who may be in a stressful state.
"MPI is doing what it is obligated to do, and that is to acknowledge the privacy rights of those farmers who have bovis identified in their herds. It's not a question of secrecy, it's about protecting individual farmers and their businesses from unwelcome and unhelpful publicity," he said.
A fourth public meeting to discuss the situation and the surveillance programme will be held tomorrow, at the Weston Hall at 6.30pm.
- Otago Daily Times
