Australia recently lifted biosecurity import controls placed on US beef that have been in place since a 'mad cow' disease outbreak in the US in 2003. Mad cow disease (bovine spongiform encephalopathy) was first detected in the south of England 40 years ago. 4 million cattle were slaughtered, and 178 people died in the ensuing years. Today, the global trade of beef and livestock remains a source of risk and anxiety. 

• Guest: Professor Matthew Baylis, chair of veterinary epidemiology at Liverpool University
• Producer: Ali Benton