INFLAMED organs in cattle could act as incubators for prion diseases such as BSE. It could mean that organs we thought were safe are a source of infection.
So far the effect has only been seen in laboratory tests on mice, but if the results hold true for cattle this could have significant implications for countries such as the US and Switzerland, which have opted for limited BSE testing programmes.
Until now, the abnormal prion proteins that cause BSE have been found only in specific organs in cattle, such as the brain and intestines. 鈥淪o the assumption has been that other parts are safe to eat,鈥� says Adriano Aguzzi, of the University Hospital of Zurich, Switzerland, who led the new research.
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鈥淐ountries with limited BSE testing have a serious consumer-protection issue鈥�
The findings add to growing evidence that prion infection can be found in other parts of the cow. 鈥淚t now seems that countries which decided not to go for broad testing, like Switzerland, have a serious consumer-protection issue which could have been prevented,鈥� says Markus Moser of Prionics, a BSE-testing company based in Schlieren, Switzerland.
The European Union tests all cattle over 30 months and some EU countries such as Germany test younger animals. The US, Canada and Switzerland only test cattle considered at high risk of having BSE, but they remove high-risk organs such as the spinal cord from all carcasses to prevent any undetected infection from reaching consumers. Because their BSE rates are so low, the US and Canada claim their limited testing is safe.
Aguzzi鈥檚 team tested mice with five different inflammatory diseases of the kidney, pancreas and liver. When they injected the mice with prions there was a build-up of these abnormal proteins in the chronically inflamed organs (Science, DOI: 10.1126/science.1106460). 鈥淭he organ transforms itself into a bioreactor for prions,鈥� says Aguzzi. He is not sure why inflamed organs are more vulnerable to prions, but speculates that it may be related to the immune reaction.
It seems, though, that inflammation does not change the severity of the brain infection, for example, by making the animals more susceptible to prion infection. Nor does an inflammatory disease speed up the progress of a prion infection in the mice.
The US Department of Agriculture and the UK鈥檚 Department for Environment, Food and Rural Affairs, which are responsible for BSE testing, say the findings do not warrant any immediate changes to regulations. Prion infectivity differs between species so the work must be repeated in cattle. Officials also say that any inflamed tissue seen in the slaughterhouse is routinely removed from carcasses along with specified risk organs.
