The startling finding is set to re-ignite debate on how a raft of deadly brain wasting diseases, caused by minute misfolded proteins called prions, are spread among deer, sheep and cattle.

The University of Californian research team, led by Nobel prize winner Stanley Prusiner, has proven laboratory mice can be infected with prions taken from the manure of deer with chronic wasting disease.

The team’s research raises the prospect of prion diseases being spread to healthy animals that graze prion contaminated manure and soil, especially in confined systems with infected animals.

In an article published in today’s edition of the noted scientific journal, Nature, the US team states: “The foregoing mechanism (ingesting manure from infected animals) is consistent with observed conditions under which captive mule deer have shown remarkably high rates of prion infection and explains how CWD could effectively transmit among mule deer in the wild.

Not only did the team show susceptible mice could be infected with prions, but that infected deer may shed nearly as many prions in their faeces as accumulated in their brains at the time of death.

“These data support the faecal-oral route as a likely natural mechanism for the transmission of CWD prions among deer and other susceptible cervid species, and possibly for scrapie prions among sheep and goats,” the researchers reported.