It sounds like the punchline to a joke, but glowing eyes may be the key to a noninvasive test allowing scientists to identify animals suffering from prion diseases such as bovine spongiform encephalopathy (BSE), better known as mad cow disease.

Researchers from Iowa State University and the National Animal Disease Centre examined sheep with scrapie – also a prion disease, and one of the prime suspects of the cause of the original BSE outbreaks, after cows were fed meal made from the remains of scrapie-infected sheep.

The research showed that the retinas of infected sheep show distinct differences in fluorescence intensity and spectroscopic signatures. The characteristic ‘glowing eye’ fluorescent signatures in the animals’ retinas are believed by the scientists to be the result of an accumulation of a fluorescent substance called lipofuscin.

“It appears that the eye, in particular the retina, is a useful tissue for noninvasive examination of some neurological pathologies such as scrapie. The development of procedures based on examinations of the eye that permit the detection of neurological disorders in animals holds great promise,” the researchers said.

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