Deep in the jungles of Papua New Guinea a mysterious, deadly disease was devastating the native Fore tribe. Each year 200 out of the 11,000-person tribe were dying from a mysterious disease. The Fore called it kuru, meaning “shivering” or “trembling,” and it effected mostly adult women and children under eight years old.
The disease was brutal. The first symptoms were lack of coordination that developed into trouble walking then tremors, stiffness, and abnormal involuntary movements. Sufferers of the disease also went through abrupt emotional changes, from extreme sadness or depression to extreme happiness with bouts of laughter, giving it the nickname the “laughing disease.” Eventually, infected people became placid and unresponsive, completely losing the ability to perform daily tasks. Death followed twenty-four months after the symptoms appeared, sometimes from secondary infections such as pneumonia or bedsores, or because of starvation due to the inability to swallow and independently eat.
The Fore believed sorcery was to blame, and the tribe was desperate for a cure as they knew they faced extinction – there were almost no women left. In 1961 Shirley Lindenbaum, a medical anthropologist, helped to identify the cause.
And it turns out that it wasn’t sorcery – it was cultural.
The Fore people believed that instead of the deceased being eaten by insects or maggots, those that respected them in life should be the ones to digest them. This task fell upon the women of the tribe as their bodies were thought to be able to control the dead’s spirit and “tame” them. However, the women would often shared the dead tissue with their children, resulting in only the women and children being the ones to fall ill.
But what was actually causing the disease? It wasn’t a bacterium, virus, or protozoan. Instead it was one of the basic structures of know life – proteins.
Since kuru, scientists have identified multiple diseases that are caused by altered proteins or prions, “proteinaceous infectious particles.” In humans Creutzfeldt-Jakob disease (CJD) and Gerstmann-Strussler-Scheinker (GSS) disease has been attributed to prions, as well scrapie in sheep, Chronic Wasting Disease (CWD) in deer, and bovine spongiform encephalopathy (BSE) in cows, famously known as “Mad Cow.”
All have similar effects on the infected individuals’ brains – a spongiform appearance with multiple holes where brain tissue should have been.
The mechanism behind how prions work is still being studied. It has been theorized that prions create a chain reaction – once they attach themselves to proteins of a similar type, they then convert the normal proteins to the altered configuration, propagating the disease.
And unlike most other disease carriers, prions have no genetic material – no DNA, RNA, or the base pair building-blocks. So how did it originate?
Yeast might have the answer.
Studies done in yeast have shown that inheritance of genetic trait from mother to daughter cell can be achieved by sharing cytoplasm, which does not contain any DNA or RNA. Proteins created in the cell nucleus are transported to the cytoplasm and from there can alter the shape of other proteins. So protein-folding chain reactions occur naturally.
But why did the protein folding turn pathogenic?
Researchers still have yet to figure it out. Hopefully, an answer comes soon as prions can exist in the environment for a every long time – up to 50 years and maybe even more. And with Mad Cow, we now know that the disease can be transferred from animals to humans, if the brain or spiral cord is ingested. Chronic Wasting Disease in deer has yet to make the jump, but it may only be a matter of time.
In any event, prions are no laughing matter.