Do you know what “mad cow’s disease” is? The name may not be that popular now, but it became known worldwide after the disease broke out in the 1980s and 1990s in the UK. The epidemic made animals dangerous, hence its name, and it was also frightening because it could be contaminated by humans.
The subject returned to the Brazilian news this week after the government confirmed that it was investigating a suspicion in Minas Gerais. This Saturday (4), the Ministry of Agriculture, Livestock and Supply (Map) confirmed the occurrence of one case in Belo Horizonte and another in Nova Canaã do Norte, in Mato Grosso.
In both cases, it is an “atypical origin” disease, that is, it did not occur because of contamination, which could affect more than one cattle at a time, but because of a mutation in a single animal.
Importing countries and the World Organization for Animal Health (OIE) have already been notified.
In 20 years of monitoring the disease in Brazil, the most traditional form has never been identified, which is when the animal is contaminated because of its feeding, says Vanessa Felipe de Souza Veterinarian, Virologist, Researcher at Embrapa Beef Cattle.
Brazil has a health status of negligible risk for the disease, since 2013, in the OIE.
The first major outbreak of the disease peaked between 1992 and 1993, when nearly 100,000 cases were confirmed in the United Kingdom. An estimated 180,000 head of cattle were affected and more than 4 million animals were sacrificed at the time.
During this period, the consumption of beef was even prohibited in that country.
Remember the crisis in an article at the time:
England studies the possibility of incinerating the herd
What is Mad Cow Disease?
THE disease is fatal and affects older adult cattle, causing nervous system degeneration. As a result, a cow that was initially calm and easy to handle, for example, becomes aggressive, hence the moniker for the disorder.
THE bovine spongiform encephalopathy, scientific name of the disease, is generated by an infectious protein called a prion. The prion is already present in the brain of several mammals naturally, including humans, however, it can become pathogenic by adopting an abnormal shape and multiplying excessively.
When this happens, the prion kills the neurons and white holes in the brain are left in their place, hence the name of the disease “spongiform”, since the holes are shaped similar to a sponge. see below.
The diseased prion kills the neurons, leaving white holes in the place, similar to a sponge. — Photo: Reproduction / Globo Rural
How is the cow contaminated?
There are two main ways for an animal to acquire the disease:
- case of atypical origin: in it, naturally, the prion mutates, becoming infectious. The older the animal, the more likely this is to happen;
- Contamination: through the consumption of feed made with contaminated animal protein, such as meat and bone meal from other species. In Brazil, the use of this type of ingredient in the manufacture of feed for cattle is prohibited.
There is no evidence that one cow transmits the disease to another, but, if she is diagnosed with the disease, the producer must put her to slaughter and incinerate the body, in order to prevent it from becoming food for some species, explains Vanessa.
The breeder must also notify the official health defense service.
What are the main symptoms?
Mad cow disease has a long evolution, in which the animal presents neurological symptoms, such as:
- teeth grinding;
- hypersensitivity to sound, touch and light;
- ataxia, that is, difficulty walking.
These symptoms can be confused with other illnesses that affect the Central Nervous System, such as rabies, intoxications, polyencephalomalacia, bovine herpes virus, among others. Therefore, it is important to prove it through laboratory diagnosis.
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There is no treatment or vaccine for mad cowTherefore, the best solution is to prevent the animal from developing the infectious protein, using only authorized rations. See more details on prevention in this booklet of the Ministry of Agriculture, Livestock and Supply.
When affected by the disease, cattle can die between two weeks and six months after the onset of symptoms.
Can humans be contaminated?
As with animals, humans can develop the infective prion naturally or acquire it from eating infected meat. In humans, there are two varieties of the disease, see below:
See the two types of disease that affects humans. — Photo: Art Editor/G1
Both diseases have some symptoms in common, such as memory loss, visual loss, depression and insomnia.
It is possible that a person has acquired the problem and they have no symptoms for years.
When identified, the patient can be treated with antivirals and steroids. However, approximately 90% of affected individuals evolve to death within one year.
Diagnosis can be made through laboratory examination. There is no evidence of human-to-human transmission, according to the Ministry of Health, except in case of contact with the patient’s blood.