There are no food safety concerns about the disease, but cows infected with it can get mastitis and arthritis and have late-term abortions, and many have to be put down.
Mr Gregan said he had changed processes on his dairy farm while awaiting more news.
A local store that would normally drop supplies at his dairy shed, for example, now left products at the farm gate.
''We're limiting stock movement and people coming on to the property, just to be safe.''
People were already planning how their operations would work if the disease was found to be widespread, he said.
''We have looked at it. Worst-case scenario, it's not going to ruin us. It's going to be another pain in the butt.''
Countries such as Australia effectively managed their dairy production in the face of the disease, so lessons were available to be learned, he said.
However, Glenavy farmer Arjan Van't Klooster, who ran an operation about two or three farms over from a farm on a restricted notice, said his approach was ''business as usual'' and he felt there was a disproportionate reaction from some to the disease outbreak.
''MPI are doing all they can, but a lot of people are over-reacting. I've heard a farmer is making sure all trucks are properly sterilised before they go on to a farm, but MPI are already making sure the trucks that visit van Leeuwen farms are.''
He was confident MPI would be able to contain the disease and eradicate it.
''I feel sorry for the van Leeuwens. It's their name getting dragged through the dirt even though, from what I know, they had nothing to do with it getting here.''
He believed the border breach and the lessons learnt would lead to better border controls in the future.
Further south, Oamaru-based farm consultant and ex-North Otago Federated Farmers president Richard Strowger said farmers were ''scared'' but all they could do was wait for the ministry to update them on how far it had spread.
The real question, he said, was how did the disease get here.
There were rumours it was from a sperm import or palm kernel, but all they could do was wait for the ministry to investigate.
Federated Farmers North Otago dairy chairman and Five Forks dairy farmer Lyndon Strang believed the disease being here would not result in job losses in the local farming sector.
''It's in every other dairying country in the world. It would be a cost to a farm owner, but I couldn't imagine it would cause businesses to go under. It would be a manageable disease.''
Other farmers approached by the Otago Daily Times declined to comment. One said they were ''over it'' already.
MPI is testing 64 farms for the disease, including the van Leeuwen farms, farms that share a border with them and farms identified as a result of movement tracing.
A spokeswoman said 29 tests had been done and sampling was continuing. So far, only two farms had tested positive.
Farmers can hear more from MPI at a community meeting at the Papakaio Community Hall today at 11am.
- Otago Daily Times