These protein-based infectious agents cause the characteristic spongy degeneration of the brain, leading to emaciation, abnormal behavior, loss of bodily functions, and death. As such, they are responsible for a group of fatal diseases referred to as transmissible spongiform encephalopathy (TSE). The group includes so-called “mad cow disease” (bovine spongiform encephalopathy, or BSE) in cattle, scrapie in sheep, and variant Creutzfeldt-Jakob disease in humans, which, according to the World Health Organization, has been “strongly linked” to eating beef products contaminated with central nervous system tissue, such as spinal cord and brain, from cows infected with mad cow disease.

Soto’s team analyzed the retention of CWD and other infectious prion proteins and their infectivity in wheat grass roots and leaves that had been incubated with prion-contaminated material. They discovered that even highly diluted amounts of the material can bind to the roots and leaves. From there, they fed the wheat grass to hamsters, which became infected with the disease.

The team also found the infectious prion proteins in plants that had been exposed to urine and feces from prion-infected hamsters and deer.

In addition, the team found that plants can uptake prions from contaminated soil and transport them to different parts of the plant. By doing this, the plants can act as a carrier of CWD.

This means, Soto said, that plants may play an important role in environmental prion contamination and the horizontal transmission of the disease. (Horizontal transmission occurs when an infectious agent is transmitted between members of the same species.)

Scientists already knew that these CWD prions are good at binding to soil, especially clay-based soils, and that they can persist there. Soto said that when some of the soil where an infected dead animal had been buried was injected into research animals several years after it had been buried, the injected animals came down with prion disease.