Scrapie could be transmitted to humans after all

Chuck Bednar for redOrbit.com – Your Universe Online

A neurodegenerative disease similar to Bovine Spongiform Encephalopathy (BSE), or mad cow disease, that typically impacts sheep and goats has the potential to affect humans, according to a new paper published earlier this month in the journal Nature Communications.

In the study, researchers from the French National Institute for Agricultural Research (INRA) report that the pathogens responsible for causing scrapie have the potential to convert the human prion protein from a healthy state to a pathological one. In mice models, the prion induced a disease similar in nature to Creutzfeldt-Jakob disease (CJD), the study authors noted.

In the wake of this discovery, the INRA scientists are calling for the transmission potential of this disease to humans to be reassessed. Scapie, like mad cow disease, is caused by transmissible pathogen proteins, but prior epidemiological studies have never been able to establish a link between the disease and the occurrence of prion diseases in humans, they explained.

The risk of transmitting scrapie to humans, also known as zoonosis, was previously believed to be “negligible because of the species barrier that naturally prevents prion propagation between species,” lead researcher and INRA scientist Olivier Andreoletti said in a statement.

Using specially designed animal models, Andreoletti and his colleagues studied the permeability of the human transmission barrier to the pathogens responsible for scrapie. Previously, this technique was used to confirm the zoonotic nature of prions responsible for BSE in cows, as well as in the variant version of Creutzfeldt-Jakob disease in humans (vCJD), the authors said.

Much to their surprise, in these rodent-based models, some of the scrapie-causing pathogens were able to cross the transmission barrier, and furthermore, the pathogens that did so were practically indistinguishable from the prions causing the sporadic form of CJD. This indicates a potential link between the occurrence of some types of the disease and these animal prions.

“Since CJD is scarce, about 1 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 Andreoletti.

“In their conclusions, the authors stress the fact that CJD cases are rare though scrapie has been circulating for centuries in small ruminants of which we eat the meat,” INRA added. “Even if in future studies scrapie is finally confirmed to have a zoonotic potential, the authors consider that this disease does not constitute a new major risk for public health.”

Other authors credited on the study include Hervé Cassard, Caroline Lacroux, Jean-Yves Douet, Séverine Lugan, Pierrette Costes, Naima Aron, Frédéric Lantier and Isabelle Lantier from INRA, and researchers from CISA- INIA in Spain, the Norwegian Veterinary Institute and the UR892 Virologie et Immunologie Moléculaires Centre de Recherche de Jouy-en-Josas in France.

Last week, researchers from New York University’s Langone Medical Center reported that they had developed the first successful vaccination against wasting disease in deer, a condition similar to mad cow disease and scrapie. The discovery, those researchers said, could help keep livestock from contracting the ailment, and could also help prevent similar infections in humans.

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