No matter what trade defences Australia erects, it may not be able to prevent domestic cases of “atypical” BSE - a cattle disease that seems to occur spontaneously, and which despite having no known health risks carries the same damaging trade implications as “classical” BSE.
Meanwhile, the world appears to be heading in the right direction for full eradication of classical BSE, the “mad cow disease” that devastated the British livestock industry in the mid-1980s and has subsequently killed 166 Britons.
With the likelihood of classical BSE being transmitted into the Australian herd now near zero, atypical BSE poses the greater threat to the beef industry, if only because of its potential effect on trade.
Atypical BSE has been found to differ from classical BSE in several ways, including the fact that it appears capable of cropping up in any herd without the feeding of meat and bone meal necessary to transmit classical BSE.
However, international trade policy currently treats the two forms of BSE in the same punitive way.
“That, in my opinion, definitely needs to be changed,” senior Commonwealth vet Dr Reg Butler told the Global Biosecurity Conference in Brisbane last week.
The Principal Veterinary Officer with the Federal Government’s Biosecurity Services Group, Dr Butler said the all available evidence points to atypical BSE being a sporadic disease, meaning that no prior presence of the disease is necessary for it to appear.
The strongest pattern to emerge to date from 51 cases of atypical BSE is related to age, Dr Butler said.
Except for a single animal in Japan, all cases have appeared in cattle older than eight years.
Atypical scrapie, the related disease in sheep and goats, has been found to be 100 times more common since it was first identified in 1998, but shows a similar pattern.
“The risk of getting an atypical scrapie case is related to flock size,” Dr Butler said.
“It’s not related to the fact that you’ve had a previous case in the flock, which is a strong indicator that it’s not a contagious disease.”
The risk of a sheep contracting atypical scrapie also increases with age, unlike classical scrapie, which is more likely to appear in animals in their first year.
The World Organisation for Animal Health (OIE) has ruled that atypical scrapie is a separate disease to classical scrapie, and reporting cases of atypical scrapie does not carry the dire trade consequences associated with classical scrapie.
“We can’t say the same for atypical BSE,” Dr Butler said.
“While scientists recognise it as a different disease, a lot of trading partners and the international standard doesn’t, and therefore it presents the same trade risk as for a country that reports its first classical BSE case.”
The United States was shut out of the Korean and Japanese beef markets, to Australia’s great advantage, because of two cases of atypical BSE and one case of classical BSE in a cow imported from Canada.
David Adams, a retired vet who formerly worked with the Office of the Chief Veterinary Officer in Canberra, told a NSW Farmers Association meeting on Tuesday that it was in Australia’s interests to work for a clear policy distinction between atypical and classical BSE.
“I think we need to be working on this at an international level,” Dr Adams said. “We don’t carry the BSE baggage that the United Kingdom and the European Union have, and we can play an important role in influencing the discussion.”
Dr Adams also told the meeting that classical BSE “is virtually gone from the world”.
Eliminating the disease, as smallpox has been eliminated, is a real possibility, he said. “There is only one mode of transmission - feeding of meat and bone meal: stop that, and you’ve stopped the disease in its tracks.”
However, Dr Butler told the Global Biosecurity conference that some work remained to be done on atypical BSE.
The disease can be transmitted from ruminants to primates by injecting primates with infected material, but it’s still uncertain whether primates, including humans, can get the disease by eating the damaged proteins.
Scientists are also unsure whether the damaged prions responsible for atypical BSE are confined to the central nervous system, or can be found in other parts of the body.