Where did she come from?
Just looking at the MPI regs, if she were quarantined on arrival it would only be if she came from a country where the below are present. I also don't see any requirement to test for piro during that quarantine? Or post-arrival?
(3)When equids are to be imported into New Zealand from countries where the diseases listed below are considered present,the duration and type of PAQ is stated in brackets:
a)Equine infectious anaemia (EIA) if considered by MPI as moderately to highly prevalent in the country of export (minimum 7 day PAQ)
b)Equine influenza (minimum 14 day PAQ)
c)Venezuelan equine encephalomyelitis (minimum 7 day PAQ)
d)Surra (minimum 30 day PAQ protected from insect vectors)
https://www.mpi.govt.nz/dmsdocument/36951-equids-import-health-standard