The good, the bad, the mad cow

Canadian officials in mid-January publicized another case of mad cow disease, formally known as bovine spongiform encephalopathy (BSE). This report came on the heels of an announcement by the Bush administration that importing Canadian beef would soon be allowed, reversing an earlier ban put in place when the first case of mad cow disease in Canada was announced in May 2003. The news is frightening to many, since eating the contaminated meat can cause variant Creutzfeldt-Jakob disease, a human form of the brain wasting sickness. Fueling this fear is a report that under certain conditions, prions – which are rogue molecules responsible for causing these diseases – can replicate in organs thought to be prion-free and safe to eat. In the report, published in the January 20 online issue of Science (1), Adriano Aguzzi and colleagues found prions in the liver, kidney, and pancreas of mice infected with a form of prion disease. It was thought that prions only inhabited an animal's brain, spinal cord, and immune system, organs that are removed from the animals before the meat is imported. The new study blurs the line between risky and safe organs and reinforces the need for beefing up inspection of animals in the food chain. Speaking to the JCI, Aguzzi warned that “BSE surveillance in the US is rudimentary.” Fortunately, the results are no cause for alarm, since the chances of contracting prion disease, only seen once in the US, are so low that a major epidemic of the human form of mad cow is very unlikely.

References

1. Heikenwalder, M., et al. 2005. Chronic lymphocytic inflammation specifies the organ tropism of prions. Science. doi:10.1126/science.1106460.