The last case that has been diagnosed in Spain has been in 2019, but these are cases that are called atypical, which are not like those of the 2000s. They occur in very old cows and nobody knows whether to relate them or not to the epidemic. The last diagnosis that is related to the boom It was in 2014 so we could say that, since 2014, we are practically safe from cases of mad cow disease.
The cause of the disease was related to the consumption of certain flours. Animals were fed with their own flesh and bones. The cows became ill when consuming those flours that were contaminated because they had been made from the corpses of animals that had the disease. After prohibiting the consumption of these flours there was a peak of cases in 2003 and 2004 when the ban began to take effect and then there was another peak that was of the animals that had consumed those flours and became older, with ages up to 8 , 9 or 10 years. After that there are only sporadic cases because, at the moment in which you control the origin of the disease, logically eradicate them.
As long as the prohibition of these flours continues in force, there will not be an epidemic of this disease again, at least with that origin. In Spain it is still monitoring all the animals that die on the farms to check if there is any positive case. If we continue with this level of vigilance and with the prohibition of these flours, a new epidemic does not have to take place.
The mad cow, whose scientific name is bovine spongiform encephalopathy or BSE, it is a prion disease. The agent that produces it is a protein that looks a lot like a protein of ours. You ingest that agent, this protein is digested, it is absorbed by the intestine and when it reaches the central nervous system, to the brain, it is able to change our proteins and make them sick. They are very similar to diseases such as Alzheimer's or Parkinson's, which we know as prion-like diseases, that is, similar to those caused by prions.
The problem that is a protein that produces it is that we do not have tools to fight them, we can not, for example, make a vaccine to prevent them.
For some time now there has also been a prion disease that affects deer and elk, it is called chronic wasting disease (CWD) and it is transmitted like the scrapie of sheep.
And the mad cow disease is not the only prion disease. There is also the scrapie of the sheep that we have known for more than two hundred years and that continues attacking the animals. In Spain, several are diagnosed a week and it is very difficult to eradicate. When there are cases, the soil becomes contaminated and the rest of the sheep that are close to the one that has tested positive can become infected. Precisely the scrapie is considered as the origin of mad cow disease because to make the meat and bone flours were used the corpses of sheep that had died for him.
The cows that ate those flours ingested the prion, absorbed it and it reached their nervous system. The first case of BSE was diagnosed in 1986. The meat of those sick cows was marketed, there were people who ate it, their organisms absorbed the prion protein, it got into their nervous system and they also got sick. That is to say, in only ten years and for the second time, the disease had once again broken the species barrier. And that was the mad cow disease.
For some time now there has also been a prion disease that affects deer and elk, it is called chronic wasting disease (CWD) and it is transmitted like the scrapie of sheep. It had only been diagnosed in the United States, Canada and Japan, but last year it was diagnosed for the first time in several northern European countries. In Spain we are quite further south, a surveillance has not yet started, but we are already working to try to diagnose it if it appears.
There is another that affects the mink, spongiform encephalopathy of the mink and another that affects the felines, feline spongiform encephalopathy, which also appeared due to mad cow disease. In veterinary medicine those are the most important. They are diseases that are controlled a lot because we already know that the barrier between species has jumped once, so they could do it again and that makes them very dangerous.
Cristina Acín She is a doctor in Veterinary Medicine, head of the technical area and quality assurance of the Autonomic Laboratory of Aragon of Transmissible Spongiform Encephalopathies.
Question done via email by Cristina Álvarez
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