Aristos Georgiou of News Week reports an international team of scientists has said that they may have identified the origin of mad cow disease. Known as bovine spongiform encephalopathy, the neurodegenerative disease destroys the brain and spinal cord in cattle, causing death.

Since BSE first appeared in the 1980s in the United Kingdom, scientists have tried to identify how the disease emerged, however, no one hypothesis has been confirmed.

For a study published in the journal Proceedings of the National Academy of Sciences, the team of scientists investigated the origins of BSE by injecting a particular variant of scrapie disease into mice which have been genetically modified with bovine DNA.

The researchers say that, unexpectedly, the injection of the scrapie strain into the genetically modified mice resulted in the propagation of classical mad cow disease prions. These prions are present in natural form in the scrapie variant.

This observation indicates that the illness could be transmitted between different species and that the modified mice could develop mad cow disease, according to the study.

Olivier Andreoletti, an author of the paper from the French National Institute for Agronomic Research (INRA,) told AFP that the modified mice are “a very good model, which works well in terms of knowing what would happen if one exposed cows to those prions.”

He noted that the results provide, for the first time, and “experimentally underpinned explanation” for the appearance of mad cow disease in the U.K. in the 1980s.

After emerging, the disease spread in cattle across Europe, North America and other regions of the globe. This process was exacerbated by the fact that cows were being given feed which contained tissue from other cows infected with the disease.