The investigation of a Papua New Guinea tribe, formerly infamous for eating human brains as part of their elaborate funerary rights, has provided insights into the development of mad cow disease and similar ailments.
Scientists from Britain and Papua New Guinea have been studying members of the Fore tribe and have discovered that their diet, which formerly included eating human brains at relatives funerals, enabled them to develop genetic resistance to a disease called kuru, which is similar to the famous ‘mad cow disease’. The research may also assist in the development of new treatments to ‘prion’ diseases, which include conditions such as Parkinson’s Disease and dementia.
Kuru first became known to the wider world after a district medical officer working in New Guinea noticed that some of the people of the Fore tribe, who live in the uplands of Papua New Guinea, were being struck down by a mysterious and fatal debilitating disease. The victims of this disease initially lost their ability to walk and this would be followed by an inability to swallow or chew. In turn, this led to weight loss and death. The disease was called by the tribe ‘kuru’, meaning “trembling in fear”. At its height, the disease caused the death of around 2 percent of the tribe per year.
The Fore tribe practiced funerary rites which included mortuary feasts where the men eat the flesh of their deceased relatives while the women eat their brains. The ritual was meant as a mark of respect for their loved ones but the tribe weren’t to know that a deadly molecule lives in human brains which causes death if eaten.
It is now known that kuru is just one of several diseases caused by proteins called ‘prions’ which have the ability to reproduce and become infectious. They generally occur in two forms called PrP-sen and PrP-res. Prions are generally manufactured by the bodies of all living beings but they can also be deformed in such a manner that they begin to turn against their host. This makes the deformed prion act rather like a virus, attacking the body and even affecting other prions around it. Those other prions then begin to mimic its behaviour, and the disease begins to spread.
The most well-known prion disease of modern times is ‘mad cow disease’, more correctly called Bovine spongiform encephalopathy (BSE) , which broke out in cattle during the 1980’s. It was identified as having been caused by cattle eating brain material from sheep infected with a disease called scrapie. The animals had been fed with the ground up remains of sheep turned into cattle feed. The outbreak of BSE in 1986 meant that hundreds of animals had to be destroyed. It also caused political turmoil across Europe and beyond. By 1988, 421 animals had been diagnosed as having the disease and in 1989 the US banned the importation of live cattle, sheep and goats from countries affected by the disease.
More worryingly, in the early 1990’s pet cats started to die after having eat pet food containing beef from BSE-infected cattle. Five antelopes in British zoos died as well, after having eaten commercial cattle feed. By 1993, 120,000 animals had been diagnosed with BSE. This caused the British government to ban the feeding of meat and bone meal to animals and also the inclusion of this material in farmyard fertiliser. However, in 1995, 19 year old Stephen Churchill was one of three people to die from variant Creutzfeldt-Jakob disease (vCJD), a new version of an already existing disease, also caused by prions. By 1996, the number of human victims in Britain had increased to 42, and 45 million cattle had been destroyed. The human deaths caused Japan to ban imports of British meat and bone animal feed and the EU to ban imports of British beef. Cases of BSE continued to appear in animals right up until 2012, although the disease had lessened considerably by then.
The problem with deformed prions, and it’s a big problem, is that they are essentially indestructible. However, it has now been found that a form of genetic protection against them exists and that this might also, going by the example of the Fore people in New Guinea, indicate that once upon a time, cannibalism was a universal practice among humans.
Eating human brains was banned in New Guinea following the outbreak of kuru in the 1950’s and the disease then began to disappear. However, scientists investigating the tribe have now discovered that the Fore tribe’s former brain-eating habits have resulted in the development of genetic resistance to kuru and other diseases caused by prions, including conditions such as Creutzfeldt-Jakob disease (CJD). The source of this genetic resistance is a specific gene that protects people against prions. In essence, it is a gene that appears to stop proteins that might produce mutated prions from producing any prions at all, thereby preventing prion diseases.
Specifically, the researchers found that where almost every other human (and vertebrate animal) has the amino acid glycine, kuru resistant Fore had the amino acid, valine. So, scientists decided to investigate the impact this variant could have. Some mice were given equal amounts of the normal protein and the variant and others were only given the variant. The results showed that while the mice from the first group were resistant to kuru and CJD, the mice with only the variant protein had become resistant to every prion strain they tested.
“This is a striking example of Darwinian evolution in humans, the epidemic of prion disease selecting a single genetic change that provided complete protection against an invariably fatal dementia” John Collinge of the Institute of Neurology’s prion unit at University College London told The Guardian .
Collinge added that his team are now conducting further investigations as the discovery may help scientists to treat a whole variety of neurodegenerative diseases such as Alzheimer’s and Parkinson’s. The way forward with this research is to understand the molecular structure of the prions that cause these diseases and the processes involved. The team have also now published their findings in the journal Nature.
BY:- Robin Whitlock