Scrapie May be Able to Cross the Species Barrier from Sheep to Humans

It turns out that the pathogens responsible for scrapie in small ruminants may just have the potential to convert the human prion protein from a healthy state of a pathological state. The findings could mean that the prion could cross a species barrier and cause problems in human populations.

Scrapie is a neurodegenerative disease that has been known for centuries. It affects both sheep and goats and is similar to Bovine Spongiform Encephalopathy (BSE), more commonly   known as mad cow disease, in that it's caused by a transmissible pathogen protein called prion.

Unlike BSE, though, epidemiological studies have never been able to establish a link between this disease and the occurrence of prion diseases in humans. In fact, risks of transmitting scrapie to humans were considered to be negligible because of the species barrier.

Yet it appears that this species barrier may not be as much as an obstacle as previously thought. In a new study, the researchers used animal models to test scrapie. In these rodent models, certain pathogens responsible for scrape were able to cross the transmission barrier. Not only that, but the pathogens that propagated through this barrier were undistinguishable from the prions causing the sporadic form of Creutzfeldt-Jakob disease (sCJD). This, in particular, suggests that there's a potential link between the occurrence of sCJD and these animal prions.

"Since CJD is scarce, about one case per million and per year, and incubation periods are usually long-several decades-it is extremely difficult for epidemiological studies to try and make this link," said Olivier Andreoletti, one of the researchers, in a news release.

The findings reveal that scrapie may have the potential to cross the species barrier. That said, more studies need to be conducted before any firm conclusions are drawn.

The findings are published in the journal Nature Communications.

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