A lack of cooperation from farmers has made officials' job of tracing the spread of Mycoplasma bovis more difficult, the Ministry for Primary Industries says.
The ministry is embarking on a years-long programme to try to eradicate the disease that is predicted to cost taxpayers and farmers $740 million.
A crucial part of the puzzle in working out how far the cow disease has spread is establishing who has received calves from the Southland farm believed to have had it first in late 2015.
Mycoplasma bovis can cause lameness, abortions and mastitis in cows, but there is no risk to human health from the infection.
MPI's Geoff Gwyn said this had been made more difficult by a lack of co-operation from farmers.
"After 10 months we've not had one scenario, and many of these names are in the public domain, who have come to us and said 'oh by the way I got animals from a property down south'.
"We have even gone out down in Invercargill and put advertisements in the newspaper with the farmer's consent and people are not coming forward and saying I traded with them."
Mr Gwyn said MPI has had to trace every farmer itself or find them through some form of testing.
"I think there's an element of looking after yourself and I can understand that, believe me getting put under regulatory control is not something you'd wish for.
"It's challenging and no matter how hard we work with you around your welfare, your herd is at risk. And I'm not sure everyone sees it in the same light around wanting to support national interests or the national herd as the rhetoric might indicate."
Keith Woodford, a former professor of agribusiness, said farmers were more afraid of MPI and being declared to be an infected property than they were of M bovis.
"That's a view in the South Island, it would be different in the North Island.
"And yes we would hope that every farmer would be totally open. But there's an awful big incentive if you have a sick calf or even a sick cow that looks like Mycoplasma bovis, there's an awful big incentive to just destroy that animal."
But farmers have their own complaints about communication.
North Canterbury farmers at an MPI arranged meeting in Cheviot were outraged at the inability of the agency to identify those with infected properties.
Dirk van Reenen said it took five months from the time testing first started to when his neighbour was finally declared to be an infected property.
He wanted to know why he was not told from the start there was a chance his neighbour was sitting on infected cattle and said knowing this earlier would have allowed him to protect his own herd.
A workaround MPI suggested at the meeting for farmers wanting to know if their neighbours were infected was to look out for the large yellow signs they were required to place at their front gates.
Farmer Mark Zino, said this was not good enough.
"Ultimately I would expect my neighbour to tell me, he shouldn't expect me to drive around the road and see a sign, or I should be contacted. At the end of the day this is a disease that we're trying to eradicate and if MPI are serious about eradicating it they need to get some laws changed."
You can hear more on Insight's investigation into mycoplasma bovis and farmer's frustrations on Sunday Morning.