Biosecurity New Zealand has been working with communities around Foveaux Strait since three oysters were found infected during a routine check.
The parasite, Bonamia ostreae, is capable of increasing mortality in oysters but little is known of the species or how big an impact it could have if it became widespread.
An update to stakeholders released on Thursday says the focus has been on increasing knowledge of the situation.
"We’ve been retesting samples of oysters collected from Foveaux Strait as part of the routine surveillance checks for the other bonamia, Bonamia exitiosa, which has been in the region for decades and is managed by the oyster fishing industry."
Testing on samples from 13 sites in the strait had been completed and Bonamia ostreae was not found in any of the 322 samples tested.
"We need further information before we can understand what these non-detect results mean and how we should interpret them."
Testing for the new bonamia from samples collected for the existing bonamia was being completed.
A rahui was placed around the area where the three infected oysters were found, and would remain in place while testing was carried out.
This was expected to be completed by late this month.
"Biosecurity New Zealand is also working with oyster fishers on the possibility of setting up the further collection of samples utilising some of the catch being landed by fishing vessels this season.
"Talks are still in progress."
Given the concern from those in the industry, a public meeting was expected to be held on Stewart Island/Rakiura along with a further meeting with interested parties in Bluff or Invercargill later this month.
Bonamia ostreae is not a food safety issue and fresh Bluff oysters remain safe to eat.
