Anthrax in hand
From the February 2008 edition of Agriculture Today.
New testing methods have helped to quickly contain the state’s worst incident of anthrax in 20 years.
Anthrax was first identified on a property near Rouchell in the Hunter Valley in late December and went on to kill approximately 50 cattle and one horse over several weeks.
Eleven Hunter Valley properties were placed in quarantine, approximately 4000 cattle on these and neighbouring properties were vaccinated and all dead animals were burnt to ash to eliminate spores.
NSW Department of Primary Industries’ (DPI) disease control program has been successful - no further deaths due to anthrax have occurred since early January.
New testing methods recently developed at Elizabeth Macarthur Agricultural Institute (EMAI), Camden, identified anthrax in samples from dead animals, using polymerase chain reaction (PCR) technology. The PCR test played a key part in DPI’s response.
The threats posed by anthrax made it vital to determine the extent of any incident and implement controls as quickly as possible.
It was particularly important because the latest incident was well outside the recognised anthrax belt across central NSW and in a region where anthrax had not been recorded since the 1940s.
NSW DPI’s food safety and diagnostics team leader, Michael Hornitzky, said the PCR technique he and his team developed was a very significant advance on previous methods of diagnosing anthrax.
He is pictured holding a culture of the deadly bacterium, Bacillus anthracis, the cause of the disease, in the EMAI high security laboratory.
"The problem with the traditional diagnostic techniques, based on examining blood smears through a microscope, is that anthrax is increasingly difficult to identify once the animal has been dead for more than a few hours," Dr Hornitzky said.
"Samples from animals dead for four, or even two, days can be too degraded for positive identification by traditional microscopy.
"The PCR test amplifies the DNA extracted from a blood sample so we can identify three characteristic gene sequences for anthrax if it is present.
"This technique allows us to quickly and definitively diagnose anthrax in samples from animals that have been dead for much longer - in this recent incident, for up to three weeks."
The effectiveness of the recent anthrax control program has been recognised at the national and international level, notably by acknowledgment of the excellence of NSW veterinarians and laboratories by ProMED, the organisation that delivers worldwide online notification of disease outbreaks.
EMAI is the key centre for diagnosing both endemic and exotic animal diseases in NSW, where PCR testing can be conducted for a broad range of other endemic and exotic diseases.
Similar technology was employed in EMAI’s virology laboratories to test for the equine influenza virus in samples taken from thousands of horses in NSW since the virus outbreak started last August.
Contact Dr Michael Hornitzky, Camden, (02) 4640 6311 michael.hornitzky@dpi.nsw.gov.au
