The bacterial cattle disease was first identified in New Zealand on one of Mr van Leeuwen's farms near Glenavy in July last year.
His veterinarian alerted the Ministry for Primary Industries after finding cow and calf sickness that did not respond to treatment.
Mr van Leeuwen, speaking to Central Rural Life just after the Government's announcement on Monday, said he now wishes he had not raised the alarm.
''It's been a complete waste of time. I should never have done it.''
He and his family would not be able to keep farming in South Canterbury, he said.
''You can't survive this sort of thing.''
He had not yet received compensation for having his herds slaughtered.
When asked what he would do in the future, he simply said, ''Pack up and go away''.
As a supplier of the nearby Oceania Dairy milk factory that he and his wife, Wilma, helped to establish with Chinese owner Inner Mongolia Yili Industrial Group, the family's departure would leave ''a huge hole there'', he said. However, he expected other farmers would eventually make up the shortfall.
He questioned how a disease could be eradicated if no-one knew how it got into New Zealand and where it was.
Oamaru Vetlife senior veterinarian Ivan Holloway, who was involved in the initial response to finding the disease, also asked how M. bovis could be eradicated when it was so hard to find using the only available testing.
He had witnessed the ''angst and trauma'' of those affected by the outbreak and cullings, although the only cattle that had showed clinical signs of disease were those at the first van Leeuwen farm, Tainui.
''All the overseas vets I talk to are astounded because it's not considered major,'' he said of M. bovis.
''If a herd is well run and animals well looked after, the impact of the disease would probably be minimal.''
The difficulty lay in people not agreeing what the disease would do to the national herd, Mr Holloway said.
''I'm not surprised (the Government) has gone down that path. I'm possibly a bit disappointed.''
''I've seen first-hand through the investigations I've been involved with the anguish on farms that have movement restriction, and the disruption to their business.''
Mr Holloway hoped new testing processes and science would enable the disease to be identified more easily.
Prime Minister Jacinda Ardern said the Government and farming leaders had agreed to a ''phased eradication plan'' that would cost an estimated $886million.
Swifter compensation would be paid to affected farmers - a substantial part of a farmer's claim for culled cows should now take four to 10 days, and a fully verified claim two to three weeks.
