Soil particles found to boost prion's capacity...( ce held infected animals could become i...)

"Since the 1940s it's been known that 'infected pastures' have the ability to infect new animals," according to Aiken.

Pedersen notes that soils are a complex mixture of organic and inorganic components that vary across the landscape and that scientists are just beginning to tease out factors in soils that may contribute to transmissibility. The new study implies, he says, "that some soils may promote the transmission of the prion agent more readily than others."

Why that's the case is unknown, Pedersen explains, but the Wisconsin team is exploring several hypotheses: that the soil particles might somehow protect the prion from degradation in the digestive system, that prions bound to clay might change the route or degree of uptake of the agent, or that the mineral somehow alters the size of prion aggregates, which have been shown to be more infectious than prions alone.

Aiken emphasizes there's still much to learn about routes of prion transmission, and the role of soil is just beginning to be explored.

"Soil is a very complex medium and we don't know what the agent is binding to" in natural or agricultural settings, Aiken says. "We do know that soil is not the only way it transmits. Animal-to-animal transmission is important, too."