Twenty-five horses remaining on the J4S Equine Nursery at Cawarall, near Rockhampton, in Queensland, have been tested, as have 11 horses that returned to eight separate properties before the property went into lockdown.
A total of three horses died at the property in the space of a fortnight, but only the last has been officially confirmed as resulting from Hendra.
Meanwhile, Australian media reports that four of the stud workers considered most at risk of contracting the virus began treatment yesterday with an antiviral drug, ribavirin, at Rockhampton Hospital.
The drug, normally used for the treatment of hepatitis, will be given intravenously for five days.
Doctors hope it will prevent the virus from developing and causing disease.
While the drug is unproven against Hendra in humans, it has proved effective against a related virus called Nipah.
Two of those receiving the drug, including stud manager Debbie Brown, were sprayed with blood and mucus from a dying horse on Saturday.
In total, 13 people are awaiting test results to establish whether they have the virus, but the four undergoing treatment are considered at greatest risk.