Paris (AFP)

Researchers believe they have established the possible origin of mad cow disease, a result which they believe shows the importance of keeping the precautionary measures in force to avoid a re-emergence of this disease.

While several hypotheses have been put forward to explain the appearance of bovine spongiform encephalopathy (BSE), or "mad cow disease", in the United Kingdom in the 1980s, none has so far been verified from experimentally.

BSE belongs to the family of prion diseases, neurodegenerative diseases that exist in many other animals (scrapie for example) as in humans (Creutzfeldt-Jakob disease). Prions, proteins that can become pathogenic by adopting an abnormal form, are different in each species.

By injecting a particular variant of scrapie in sheep ("AS pouratypical scrapie") into mice making the prion of bovine origin (following genetic manipulation), the researchers showed not only that this disease had the ability to cross the species barrier but that transgenic rodents were developing BSE, according to their article published in the American scientific journal PNAS.

Genetically modified mice of this kind are "a very good model, which works well to know what would happen if we exposed cows to these prions", explained to AFP Olivier Andreoletti, researcher at the National Institute of agricultural research (INRA), which directed the study.

"These results are explained by the presence of small amounts of classical BSE" naturally in the prions of AS, details INRA in a press release.

"For the first time, these data provide an experimentally substantiated explanation for the onset" of mad cow disease in the mid-1980s in the United Kingdom.

BSE then spread among cattle across "Europe, North America and many other countries" presumably through their diet containing meal of carcass and offal from animals (cattle or sheep) with spongiform encephalopathy.

The exposure of consumers to products from cattle infected with BSE has been the source of the emergence of a variant form of Creutzfeldt-Jakob disease.

In Europe, health measures taken in the 1990s (ban on animal meal, surveillance of cross-contamination, destruction of the highest risk tissues, etc.) have considerably slowed down the curve of the epizootic.

"These measures are still in place, but they are very expensive", which pushes manufacturers and certain health officials to push for their elimination, "to start recycling these good quality proteins" instead of throwing them away, seeing an alternative to importing soybeans, observes Olivier Andreoletti.

But "if there is a proven source of BSE, repeating these non-virtuous practices" runs the risk of seeing the disease re-emerge, warns the researcher.

© 2019 AFP