All three of Matt Cumani's stable blocks and one belonging to his Ballarat neighbour James Wardeiner have now been quarantined to contain a case of the infectious disease strangles.

A horse trained by Cumani was diagnosed on Wednesday with strangles and the stable block where it was housed was isolated.

After a further inspection on Thursday, Racing Victoria stewards expanded the quarantine to include all the Cumani horses and those of Wardeiner.

"As a result of their investigations today the stewards have ordered that all three of Mr Cumani's stables be quarantined due to the recent movement of horses between them," an RV statement said.

"Further, as Mr Cumani has also had horses stabled in the same stable complex as Mr Wardeiner this month, that stable complex has also been quarantined as a matter of precaution."

Stewards have advised Cumani and Wardeiner that no horses are allowed to leave their stable complex to train, race or attend another location until approval is granted by RV.

RV says there are no restrictions at this time on any other Ballarat trainers, nor has training at the Ballarat Turf Club been suspended or any conditions imposed.

Stewards have begun an investigation into the circumstances of the infection and the timing of the notification by Cumani.

Strangles is an infectious bacterial condition that is transmitted via direct contact between individual horses and/or through indirect contact in several ways including contaminated feed, equipment and transport vehicles.

Strangles usually causes upper respiratory tract disease, but can also affect the lungs. It is highly contagious although rarely fatal.

Cumani issued a statement on Thursday morning on his website announcing he had an infected horse.