The number of cattle and deer herds infected with bovine tuberculosis (TB) is at an all-time record low.
Animal health agency OSPRI said the numbers had dropped below 40 for the first time, with 34 cattle herds and two deer herds infected.
The infection is spread mainly by possums, and can cause serious production losses and animal welfare issues.
Farmers and agricultural authorities have been battling it since the 1950s.
OSPRI programme development group manager Stu Hutchings said this was a great achievement towards the goal of eradicating TB by 2026.
"It's a real milestone and it's a credit to all of the farmers and other industry participants involved in our TB-free programme," he said.
"It's a big step towards New Zealand becoming TB-free. The aim of the new plan that's currently under proposal and about to go to the minister, is that we will have all of the herds with TB freedom by 2026."
He said the number of infected herds had been reduced from about 1700 in the mid-1990s to the current level of 36.
"It was as high as 71 last year, so we're making good progress... We've achieved nearly 1.1 million hectares of TB eradication of wildlife out of our target of 2.5 million hectares."
Mr Hutchings said while this was a significant step, people needed to remain vigilant during times when stock were heading to processing works.