A ferret survey is being undertaken in the Mt Cargill area, near Dunedin, after last year's bovine Tb outbreak.
Four herds of cattle and deer were identified as infected with Tb.
In a recent update, TBfree southern South Island programme manager Brent Rohloff said work had been progressing well.
OSPRI was using a combination of herd Tb testing, controls on animal movement for infected herds, and survey and control of wild animals to eradicate Tb from the area.
As Tb had been found in six possums and one ferret, further surveillance work was needed to determine the extent of the infection in local wildlife.
The ferret survey, undertaken by a TB free contractor, was expected to be finished by the end of this month.
Ferrets scavenged Tb-infected possums and could become infected with the disease which made them "extremely important'' indicators of whether Tb was present in an area.
Trapping was being used for the survey and carcasses would be sent for postmortem examination.
Further possum control and surveys would be done during this year and next year.
The infected herds were subject to an ongoing intensive Tb testing programme until they were free of the disease.