Mad cow disease is an ominously trickster neurodegenerative condition that can take about one to eight years to become evident. What causes mad cow disease? Read ahead to find out.
Mad cow disease is the layman’s colloquial for bovine spongiform encephalopathy. This is a neurodegenerative condition that affects the brain and spinal cord, leading to the formation of sponge like perforations in the brain and spinal cord tissues. This condition keeps progressing over time and leads to complete neural degeneration and, ultimately, the death of the affected organism. The symptoms of mad cow disease manifest by way of the infected subject having difficulty in standing, moving or maintaining balance. This disease has a pretty long incubation period and initial symptoms can take anywhere between two and a half to eight years to become noticeable, making early diagnosis near to impossible.
Also, the pathogenesis of this disease is such that the immune system of the affected organism is tricked into ignoring the growth and spread of the disease-causing agent inside the body. So, what causes mad cow disease and why is it so difficult to diagnose this condition immediately after the infection enters the subject’s body? The subsequent segment attempts to answer both aspects of this query.
Mad Cow Disease Causes
While mad cow disease is transmitted to healthy cattle and humans through consumption of contaminated meat from infected cattle that died from this condition, the disease itself is caused due to a biological mischief played by a trickster protein, prion. A prion is a protein which is incorrectly folded. By incorrect folding, it is meant that the protein is formed into folds that are detrimental to their functional capacities. Incorrectly folded proteins are associated with a number of neurodegenerative diseases such as Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, amyloid cardiomyopathy, polyneuropathy, mad cow disease, etc.
When a prion or misfolded protein is transmitted to a healthy host from an infected one, it influences the surrounding well folded proteins and causes them to become misfolded themselves. Since these prions are proteins and do not have the nucleic acids contained by conventional pathogens like bacteria and viruses, the immune system does not identify them as threats to the body and simply turns its attention away from the phenomenon where each converted prion turns other properly folded proteins into prions, an ominous chain triggered by a single prion that got transmitted to the healthy host.
Debate Over Pathogenesis
Now, there is still a lot of debate over how these prions come to be in the first place. Some suggest that a mutation in the gene that regulates the normal structure and folding of proteins is the culprit while some others suggest that an imbalance of nutrient metals in the brain caused by the brain’s inability to stabilize its internal nutritional environment is the reason behind formation of prions. There are yet others who believe that a kind of slow virus in the system tampers with healthy protein folds to turn them into prions.
However, due to the absence of an immune response to prions, the grounds of the virus and neural homeostasis theories tend to become somewhat shaky. Also, the fact that prions convert other proteins inside the host’s body, thereby, reproducing or spreading in a way, also raise serious doubts over the absence of conventional pathogens as replication or reproduction is possible for only those cells or biological particles that contain nucleic acid, which is absent in proteins and prions alike.
Although primarily a disease affecting bovine cattle, mad cow disease has been known to have been transmitted to human subjects as a result of consumption of contaminated meat which came from cattle that succumbed to this disease. Although the strongest possibility of infection exists when the affected parts – neural tissues of the brain and spinal cord – are consumed, infection can also occur when any other part of the infected animal’s body or any fluid from it is consumed by unwitting humans.
This raises another question – how do cattle, which are primarily herbivores, get mad cow disease? Well, although bovine cattle is a strictly vegetarian lot, recently, food and protein supplements in the form of meat and bone meal, which often contains remains of animals post slaughter, have led to healthy cattle getting infected as many of those slaughtered animals were infected with mad cow disease. Meat and bone meals are a cheaper protein substitute to soy bean meals in most European countries where soy bean does not grow abundantly, hence, the preference of the former over vegetarian protein supplements.