A small, Auckland research firm is developing a more sensitive test for Mycoplasma bovis.
The most recent figures show just 327 properties under active surveillance versus 589 just a week earlier.
The number has consistently been at least 500 – and as high as 640 – since the so-called surge in May.
MPI says the 40% drop is due to several reasons, firstly that many farms have recently completed surveillance and been found clear.
It adds that farms are also starting to get through sampling and testing quicker, due to the changes in sampling requirements to only one negative round for most management groups.
MPI also claims a new data management system is providing more timely and accurate reporting.
The total number of confirmed infected properties now stands at 195 – with 176 cleared and 19 still active. 310 farms are now under a notice of direction.
MPI says it has slaughtered 117,591 animals and paid out compensation of $98.6 million from 1156 claims either completed or partly paid from 1486 claims received so far.