Ames, IA--Scientists at Iowa State University have discovered a way to detect a disease called scrapie in sheep using fluorescence spectroscopy. The eyes of sheep infected with scrapie--a neurological disorder similar to mad-cow disease--return an intense, almost-white glow when they're illuminated with blue excitation light, says Jacob Petrich.
The accidental discovery occurred while Petrich and his collaborators were developing a fluorescence spectroscopy device used in slaughterhouses to test livestock carcasses for possible E. coli contamination.
"One day we were testing the apparatus by shining light on the carcass and we saw the spinal cord glow--it fluoresced," said Petrich, professor and chair of Iowa State's chemistry department. "We saw the spinal cord through the skin."
The findings suggest technologies and techniques can be developed to quickly and non-invasively test for transmissible spongiform encephalopathies, progressive and fatal neurological diseases such as mad-cow disease in cattle and Creutzfeldt-Jakob disease in humans. Petrich, in fact, is working to develop a testing device.
Petrich and a team of researchers began studying the feasibility of a fluorescence test. The researchers collected 140 eyeballs from 73 sheep. Thirty five of those sheep were infected with scrapie; 38 were not. The researchers took fluorescence readings from various parts of the eyes of all the sheep.
"The bottom line is the scrapie-positive retinas fluoresced like crazy," Petrich said. "And the scrapie-negative ones did not."
A previous study published in Veterinary Pathology (doi: 10.1354/vp.08-VP-0206-W-FL) reported that the function and structure of retinas are altered in cattle infected with transmissible mink encephalopathy. Other studies have reported that lipofuscin, an intracellular fluorescent pigment, accumulates in the eyes of animals infected with the neurological diseases. Petrich and his team attribute the glow from scrapie-positive retinas to the elevated levels of lipofuscin.
Subscribe now to Laser Focus World magazine; it’s free!
