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Industry awaits tests to learn if BJD impact will spread

James Nason, 06/02/2013

Bovine Johne’s Disease test results expected soon could see more properties released from movement restrictions, but there is also a chance significantly more could be added.

The detection of the wasting disease in three cattle on a Central Queensland cattle stud last November triggered a major trace-forward, testing and eradication program as Queensland Government and industry leaders moved to protect the State’s “BJD protected zone” status.

Initially 170 properties that had received cattle from the stud were subjected to movement restrictions as biosecurity officers began tests to determine whether BJD had infected their herds.

The Queensland Government told Beef Central on Monday that the number of properties now under movement restrictions has been reduced to 121, and it was continuing to work to release properties from quarantine as quickly as possible.

However there is a possibility that new properties could be added to the list as important test results are returned in coming weeks.

Early last month the Queensland Government confirmed that preliminary histology tests conducted as part of its trace-forward program had identified two animals with suspected BJD on two additional properties.

Both animals had originated from the Central Queensland cattle property where the incursion was first identified.

The Queensland Government has since been waiting for the results of more definitive tests on faecal samples to prove if the cattle have BJD, and, if so, whether more properties will have to be placed under quarantine.

Departmental sources have indicated that one of the properties with suspected BJD is a stud, and that preliminary trace-forwards using NLIS records have indicated that around 100 properties could be affected if BJD is confirmed in the animal from that stud.

In response to Beef Central’s questions regarding possible new quarantines, the Queensland Government said it was awaiting the results of more definitive tests on the suspect animals.

“Trace-forward assessments are being undertaken from the two suspect properties, however a full risk assessment cannot be undertaken until it is clear whether the suspect animals are shedding BJD organisms,” Biosecurity Queensland Chief Veterinary Officer, Dr Rick Symons said in a written statement. 

When Biosecurity Queensland confirmed on January 9 that two animals had tested positive to likely BJD on histology tests – which can produce ‘false positives’ – Dr Symons said faecal samples were being sent to Sydney to be tested with the new and faster PCR test, which takes up to two to three weeks to return a result.

At the time Dr Symons said a positive response to the faecal samples using the new PCR test would be deemed as “definitive” proof the animals had BJD.

A negative PCR result could not be deemed as definitive evidence that an animal was BJD-free, however, because it was possible for an infected animal to be not shedding bacteria when its faeces sample was taken. As a result, in the case of a negative PCR result, a longer-running faecal culture test would still be required, Dr Symons said at the time.

Almost four weeks has passed since that time, however, if the Government already has results from the two-three week PCR testing procedure in hand, which would seem likely, it is not saying.

“Biosecurity Queensland provides test results directly to the submitter or owners and does not routinely release all test results publicly,” it stated.

“If any test results need to be made public this will be done at the time.”

A departmental source told Beef Central privately that the department was likely to be waiting for the full results of the faecal sample test, rather than the PCR test, before making a determination on whether new trace-forward quarantines will be required.

The source indicated the results of full faecal culture tests on the suspect animals were expected in the next “week or two”.

The BJD incursion and the associated need to test samples from as many as 170 properties has placed pressure on the Queensland Government’s testing resources, at a time when it is transitioning from three laboratories down to one, as part of a cost-cutting move announced by the Newman Government last year.

A significant increase in the properties placed under movement restrictions would place even further strain on the system, however the Queensland Government maintains that its testing capacity is adequate.

“Biosecurity Queensland remains confident that laboratory capacity is sufficient to manage the level of submissions,” Dr Symons said.

“As of 29 January 2013, laboratories have received samples from 70 properties and 2218 animals.

“While the PCR test is being established in Queensland, samples have been sent to EMAI in New South Wales for PCR testing with a further 276 samples being sent on 29 January 2013.

“Arrangements remain in place for additional tests to be conducted interstate should they be required.”

• The Queensland Government has provided a comprehensive fact sheet which outlines how BJD assessments work, the tests that can be used and strategies for managing the disease, which can be viewed by clicking here 

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