SYDNEY (REUTERS) - Australia, the world's No. 3 largest beef exporter, said it has confirmed that approximately 40 head of cattle have been killed by anthrax, but it expects the impact of the disease has been curtailed.

The outbreak was found at two properties in Moree, north-west New South Wales, the New South Wales Department of Primary Industries (DPI) said.

The government department said all remaining cattle have now been vaccinated, and there have been no further deaths on either property since March 9.

"Extensive tracing has confirmed that animals have not left the property and that the disease has not spread to other properties," Mr Steve Green, a spokesperson for the DPI, said in an emailed statement to Reuters.

Scientists said the outbreak is rare but not unusual.

The disease is contracted through contact with spores, which are mostly released by dead animals but can remain in the ground for years, experts said.

By quarantining those areas where the outbreak occurs, Dr David Beggs, a lecturer in cattle in the Faculty of Veterinary Science at the University of Melbourne, says the disease can be successfully contained.

The Australian Department of Agriculture, Fisheries and Forestry forecast in December that beef and veal exports would rise 3 per cent in the 2012/13 marketing season in March.