Department of Primary Industries (DPI) Deputy Chief Veterinary Officer Dr Sally Spence said the virus has been confirmed by a virologist at DPI’s Elizabeth Macarthur Agricultural Institute and the affected properties have been placed in quarantine.

"The affected flock in western Sydney consists of around 50 pigeons," Dr Spence said.

"It is believed that the virus may have been transmitted following the introduction of three new pigeons that were purchased at a bird auction last month.

"The purchased pigeons became ill shortly after the auction and subsequently transmitted the virus to the loft.

"The pigeons from the south-western Sydney flock are believed to have contracted the virus from a race from Mudgee on 16 June.

"This is the same event where pigeons from another flock were affected last week."

Dr Spence is urging pigeon owners to put in place good biosecurity practices to reduce the likelihood of further cases in NSW.

"Good biosecurity, including preventing direct or indirect contact with other racing, fancy or wild pigeons can minimise the risk," Dr Spence said.

"Pigeon owners should also be on the look out for signs of the virus which can include increased thirst and diarrhoea, loss of appetite, and reluctance to move and fly.

"Pigeon paramyxovirus also causes neurological symptoms such as trembling of the wings and head, tumbling on landing, partial paralysis of the wings and legs and head flicking before death."

Following the recent cases, the DPI has introduced a new control order which restricts the aggregation of non-vaccinated pigeons by banning gatherings and competitions, including organised market sales, shows and racing events in NSW.

"These events can only take place if all birds taking part are certified as fully vaccinated," Dr Spence said.

"Clubs that wish to organise a race meet or other form of gathering must ensure that all participating pigeons have been fully vaccinated.

"All pigeon owners will be required to fill out a declaration form and submit it to the organiser of any race, sale or show in which they would like to take part."

Biosecurity tips and further information on the pigeon paramyxovirus is available at http://www.dpi.nsw.gov.au/biosecurity