By studying prions, researchers from Toulouse in France have identified the origin of bovine spongiform encephalopathy, better known as the “mad cow disease”. They then warned of the possible return of the disease.
Cattle
Bovine spongiform encephalopathy (BSE), is a degenerative infection of the central nervous system of cattle. The disease appeared in the 1980s in the United Kingdom before spreading to Europe and North America in the 1990s. Today, researchers in Toulouse have found the possible origin of this disease and warn of its possible reappearance. The results of this study were published on Monday 16 December in the journal Nature Communications.
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For their work, the researchers from INRA (Institut National de la Recherche Agronomique) and ENVT (Ecole Nationale Vétérinaire de Toulouse) worked with prions. These are proteins that can become pathogenic by adopting an abnormal form, which is different in each species. More specifically, they used the prion that causes scrapie in sheep and injected it into rats genetically modified to make the bovine prion.
Result of the experiment: in 95% of the cases, the rodents developed a bovine spongiform encephalopathy. These genetically modified mice are “a very good model, which works well for finding out what would happen if cows were exposed to these prions,” explains Olivier Andreoletti, an INRA researcher who led the study.
Today, the food chain is protected
For the first time, these data provide an experimental explanation for the emergence of mad cow disease in the mid-1980s in the United Kingdom, INRA says in a press release. BSE was then transmitted among cattle throughout Europe, North America, and many other countries, probably through a diet rich in meat and bone meals and offal from diseased animals.
By consuming products from infected cattle, several people developed a variant of Creutzfeldt-Jakob disease. Europe began to ban meat-and-bone meals, monitor for possible cross-contamination, and destroy the highest-risk tissues, which significantly slowed down the outbreak.
“Today the food chain is protected by these measures and as a result, there are no more cases of contamination and we have almost eliminated BSE,” explains Olivier Andreoletti. Only a few cases remain, such as the one detected in the Ardennes in 2016.
The risk of an epidemic has not completely disappeared
However, the risk of an epidemic still exists. “Despite the economic cost of these measures and the virtual disappearance of BSE cases, the risk of a re-emergence of BSE from atypical scrapie cases in small ruminants argues for the maintenance of the most fundamental measures (ban on meat and bone meals, systematic removal, and destruction of the highest risk tissues, etc.) which have made it possible over the last 20 years to protect consumers and production chains from “mad cow disease”,” says the INRA.
“The measures put in place are costly and there is now pressure from the industry. Some are talking about lifting the ban on recycling carcasses into meat and bone meals. We are not here to give lessons, but to produce knowledge,” says Olivier Andreoletti, who fears that the European Commission will accept the return of meat and bone meals to the market. For the researchers, “if we start using the same practices again, we will have the same effects”.
“Prion diseases are neurodegenerative diseases that cause progressive neurological disorders with fatal results after a long and silent incubation period. They affect humans (Creutzfeldt-Jakob disease), farm animals (mad cow disease, scrapie in sheep and goats, dromedary prion disease), and wild animals (chronic deer wasting disease),” INRA explains on its website. The symptoms can be locomotor, sensory, and behavioral.
FAQ: Understanding Mad Cow Disease and Its Possible Return
1. What is Bovine Spongiform Encephalopathy (BSE)?
BSE, or mad cow disease, is a degenerative and fatal infection of the central nervous system in cattle, caused by abnormal prion proteins.
2. How did BSE originally emerge?
Researchers suggest that BSE originated from prions found in scrapie-infected sheep. When these prions were introduced into cattle through contaminated meat and bone meal, they mutated, leading to the disease outbreak.
3. How was BSE transmitted?
The disease spread among cattle through the consumption of animal-based feed containing infected tissues. Humans contracted a variant, Creutzfeldt-Jakob disease (vCJD), by consuming infected beef.
4. How was the mad cow disease outbreak controlled?
Strict regulations were implemented, including bans on meat-and-bone meal, monitoring of cross-contamination, and removal of high-risk tissues from the food supply. These measures significantly reduced BSE cases.
5. Is there still a risk of BSE returning?
Yes, researchers warn that BSE could re-emerge from atypical scrapie cases in sheep and goats, emphasizing the need to maintain strict preventive measures.
6. Why are scientists concerned about policy changes?
There is pressure from the meat industry to lift bans on recycling carcasses into animal feed. Scientists caution that reintroducing such practices could lead to another BSE outbreak.
7. What are prion diseases, and do they affect humans?
Prion diseases are fatal neurodegenerative disorders caused by misfolded proteins. In humans, this includes Creutzfeldt-Jakob disease (CJD), which is linked to consuming contaminated beef.
8. What are the symptoms of prion diseases?
Symptoms include motor dysfunction, sensory issues, and behavioral changes that progress over time, ultimately leading to death.
9. Are there still cases of BSE today?
BSE has been nearly eradicated due to strict regulations, but occasional cases, such as one in the Ardennes in 2016, highlight the need for continued vigilance.
10. What is the key takeaway from this research?
The study confirms the likely origin of BSE and warns that lifting existing safety measures could lead to a resurgence of mad cow disease.
References
Huor, A., Espinosa, J. C., Vidal, E., Andreoletti, O., & Oldstone, M. B. A. (2019). The emergence of classical BSE from atypical/Nor98 scrapie. Proceedings of the National Academy of Sciences, 116(52), 26853–26862. https://doi.org/10.1073/pnas.1915737116
