News

Qld BJD outbreak linked to foreign bison strain

James Nason, 15/05/2013

Ever since Bovine Johne’s Disease was confirmed in a Central Queensland cattle stud last November, triggering the quarantine lockdown of more than 100 cattle properties across northern Australia, a question on everybody’s lips has been ‘how did it get there?’

Laboratory testing of the strain of BJD found on the Kirk family’s Rockley Brahman stud has now come much closer to solving that riddle – and the answer raises some serious questions about the biosecurity protections in place for Australia’s national cattle herd.

Queensland Government scientists have now determined that the strain of BJD found on Rockley is the “bison-strain”, which means it is very likely to have originated from overseas.

The strain is unlike any other found in Australia, ruling out the likelihood that that variant at the centre of Queensland’s quarantine response was imported via cattle from either Victoria or New South Wales.

While the term ‘bison-strain’ narrows the possible sources of the original infection to cattle imported from North America, Asia or Europe, the fact that large numbers of bulls were imported to Central Queensland from the United  States in the 1980s points to that country as the likely origin.

That theory is also supported by recollections from the Kirk family of a single imported bull in the 1980s that exhibited symptoms they would now recognise as classic signs of BJD.

That particular US bull was imported by a syndicate of Queensland studs and, after serving for a season at a stud in north Queensland, it was transported by train to Rockley.

“If anyone said have you seen an animal on your place that may have shown clinical signs, that is probably the only animal we could think of that had chronic wasting and diarrhoea,” Mr Kirk said.

Further testing needed: Biosecurity Qld

Biosecurity Queensland chief biosecurity officer Dr Jim Thompson, Chief Biosecurity Officer, confirmed in a statement to Beef Central this morning that preliminary results indicated the bison strain of BJD, which had not been previously found in Australia.

“Further testing will need to be conducted to substantiate the initial findings of the bison strain – and until this is completed, we cannot speculate on the origin of the infection,” Dr Thompson said.

There are two known strains of Johne’s disease in Australia, the cattle strain and sheep strain.

The cattle strain infects mainly cattle, alpaca, goats, deer and camels to cause BJD, while the sheep strain infects mainly sheep and goats to cause ovine Johne's disease, but is also known to have been previously detected in cattle.

Bison strains have been reported in North America, India and Africa, and are known to cause disease.

“The suggested findings will not impact, or change the ongoing BJD disease investigation and response in Queensland,” Dr Thompson said.

Federal role

The finding raises questions about whether the Federal Government should take more responsibility in helping those affected by the latest outbreak, given that the likely overseas origin of this Qld strain points to a failure in AQIS’s biosecurity  protection systems at some point and its Cocos Island quarantine station.

Many imported bulls are brought into Australia at young ages, largely because younger bulls are better equipped to adapt to new environments, and because it is less expensive to transport younger, lighter animals than older, heavier ones.  Infected animals often do not exhibit clinical symptoms at young ages, which may partly explain how an infected import may have slipped through the quarantine inspection net.

Ashley Kirk questions why the cattle industry should be left to pay for the costs of the BJD outbreak via a levy when producers believed they were protected from off-shore diseases under the Federal Government’s quarantine programs.

“Biosecurity is in their hands, they are the ones controlling it, and if they have let us down, why should it then be left up to industry to collect the money to pay for the problem?”

He said he believed the bison strain finding contributed to the argument that producers should be able to self-manage the disease at farm level with the use of vaccines, as they already do for a range of other diseases.

The Kirks estimate that the existing control and quarantine program will cost their own business at least $400,000 in lost animal sales a year for many years to come, without counting the costs of ongoing testing and quarantine impositions and the damage to their stud’s respected industry standing.

Qld herd prevalence

The indication that the Qld strain is of foreign origin and may have been actively spreading since the 1980s raises the prospect that BJD could be endemic in the state’s beef herd and, for all practical intents and purposes, ineradicable.

When BJD was discovered on Rockley last year, NLIS records allowed the movements of bulls to client properties to be traced back for the previous seven years. That led to 170 properties being caught up in movement restrictions as authorities commenced testing to determine if BJD had spread to their herds.

(As an update – 15 trace-properties which received Rockley bulls in the past seven years have since returned positive results, with further testing underway to confirm those results. Movement restrictions are still in place of 57 Queensland properties).

If it is proven that BJD has been present in Queensland's herd since the 1980s, the task of tracing movements so far back could be all but impossible.

Establishing exactly how prevalent the disease is in the state's herd remains one of the key challenges for industry and Government leaders as they plot the course ahead, and decide if an eradication-focused policy is still an achieveable or viable goal. 

There is some speculation – not officially verified – that state decision-makers are considering implementing a screening program in abattoirs in future to monitor the prevalence of BJD in cattle sent to meatworks.

While that would help to provide an accurate picture of how widespread BJD is in the Queensland cattle herd, if conducted with the control and eradication policy still in place, it would also expose producers to the potential nightmare of having their operation placed under quarantine lockdown if a consignment of their cattle sent to an abattoir was to test positive to the disease.

While the number of properties under movement restrictions has been reduced to 57, some of those properties are expected to remain subject to quarantine restrictions for a matter of years before they can be formally cleared of the infection.

Meanwhile the industry is awaiting further details on the voluntary biosecurity levy and compensation package the Queensland Government is planning to announce, and the results of the Finlay Hill review into Queensland’s handling of the BJD issue to date, after the final report and recommendations were handed to the minister at the end of April. 

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