The Ministry for Primary Industries says testing of wild flat oyster stocks in Foveaux Strait fisheries showed the Bonamia ostreae parasite was not present in any shellfish.
The parasite was discovered in May in fisheries on Stewart Island, and a large-scale cull was ordered.
The MPI said that appeared to be a smart move, as the wild stocks there now appear to have avoided the parasite.
MPI director of readiness and response Geoff Gwyn said surveillance of oyster fisheries has been stepped up from bi-annually to four times per year.
"Continued surveillance will ensure the ministry can move quickly if a new infection appears in the future," he said.
Bonamia ostreae can devastate oyster stocks quickly, and it has been in New Zealand since at least 2015 when it was found in shellfish in Marlborough Sounds and Nelson.
Removal of oysters from Big Glory Bay finished on September 6, MPI said, but removal is still taking place in Marlborough.