How did PNG villages thrive when the women were wiped out by disease?

One of the most in depth genetic population studies of people from the Highland villages in Papua New Guinea has thrown up fascinating insights into internal migration and tribal culture, and might have solved the riddle of how some villages survived despite a devastating disease wiping out most of their women.

The study of the Fore people of the Eastern Highlands region included oral and genetic histories, and began nearly 70 years ago, when western scientists discovered vast numbers of women and children were dying of a debilitating illness.

When it was first investigated in 1957, the illness, known locally as ‘kuru,” was present in “epidemic” proportions, with 1000 deaths between 1957-1961. In some villages, the whole female population was affected, with the prevailing wisdom blaming ‘sorcery.’ The youngest victim was 4, the oldest 60.

The term kuru derives from the Fore word kuria “to shake” or “trembling” which describes the body tremors that are a classic symptomof the disease.

Based on oral histories researchers believe the kuru epidemic was thought to have started in around 1910-20, it reached a peak in the 1950s and the number of deaths declined till there were none by 2008.

It had come quickly, as if out of nowhere, and declined within about three generations.

Early researchers quickly identified that it was a large-scale prion disease  ̶  a rare progressive neurodegenerative disorder – and they understood the mode of transmission: the Fore people had a cultural tradition of eating the entire bodies of deceased relatives, which led to the spread of kuru, an always fatal neurodegenerative disease lasting, on average, 12 months, that spread as people consumed infected tissue during traditional feasts, with women and children particularly affected.

Kuru was found only among the Fore people and their immediate neighbours in the Okapa District of the Eastern Highlands Province of PNG.

By 1967, it was shown that kuru was a transmissible spongiform encephalopathy (TSE). A second human spongiform encephalopathy, Creutzfeldt–Jakob disease (CJD), was reported to be transmissible in 1968.

A fascinating account of the process by which kuru was investigated is contained within a “personal perspective” 2008 paper by epidemiologist Michael Alpers, who worked at the Centre for International Health at Curtin University in Western Australia, and at the Prion Unit in the Department of Neurodegenerative Disease, at University College London. He writes, eloquently:

There were many remarkable things about the people of the kuru-affected region; one was the means of disposal of the dead, which was normally by consumption of the body by the dead person’s kin.

“Owing to the derogatory connotations of the word ‘cannibalism’, which are only softened a little by the more technical ‘endocannibalism’, I have adopted the term ‘transumption’ to describe the mode of disposal of the dead practised by the Fore and their neighbours: this is ‘the mortuary practice of consumption of the dead and incorporation of the body of the dead person into the bodies of living relatives, thus helping to free the spirit of the dead’. There could also be considerable benefits to the living from this practice, but it was fraught with many dangers.

“The whole body was eaten by the female relatives and their children of both sexes. Adult males, which included boys above the age of approximately 7 years who were living in the men’s house, rarely partook of the body and never ate the brain or other internal organs.

The practice had been proscribed by the Australian administration as one of their first acts of ‘control’ and public feasting had ceased by the mid-1950s and the practice abandoned by the early 1960s.

“…the origin of kuru still remained an unsolved question. The solution proposed…is now generally accepted: that kuru arose in a single individual from a spontaneous change that created a pathogenic, infectious agent in the brain. Such a chance event, though rare, leads to sporadic CJD in approximately one person in every million each year in all human populations.

“The practice of transumption is in itself not risky and many communities outside the kuru-affected region practised it with impunity.”

The link to CJD, and the curiosity to answer some remaining questions, including how did the tribes survive when their women died, has resulted in ongoing epidemiological research.

PNG is home to 850 languages among its 8m or more people. Villages across a river from each other might have entirely different languages. There is in some areas constant fighting, and it’s generally believed that villages don’t mix very much.

In addition sorcery and the belief in spirits is widespread, and it too seems to add to the expectation that people would not willingly travel into a new community where there was death on a large scale.

But in a new paper researchers show genetic evaluation disproves this and explains how the community survived this disease. The researchers noted the prevailing wisdom which was: “…that kuru led to a decrease or even a complete cessation of intermarriages between the Fore and neighbouring communities, because those communities linked kuru to sorcery, which made them fearful of the Fore.”

The authors say: “In our data, we observed no evidence…for less overall migration into areas with high kuru incidence. On the contrary, we observed a significant bias toward females among migrants into high kuru incidence areas.

Researchers collected oral history from elderly people in the region and genetic samples from the population.

They say some of the elderly women who survived the feasts carried genetic variants that likely made them immune, “…and the genetic variance within the community suggested large numbers of women migrated into the community, which likely helped them survive despite high fatalities among local women.”

The research was part of an international collaboration between 1996-2012.

It was led by a team from the Medical Research Council (MRC) and the Institute of Prion Diseases (IPD) in London, and included the first large scale genetic testing of villages in the EHL.  The PNG Institute for Medical Research (PNGIMR) was a partner.

“We navigated one of the most complex landscapes possible in terms of geographical, cultural and linguistic diversity and set the scene for future genetic epidemiological work,” says Liam Quinn, the paper’s first author at the University College London and University of Copenhagen.

One member of the team, Jerome Whitfield a medical anthropologist, lived in the village of Waisa in the South Fore and worked with the PNGIMR field team staff who were recruited from kuru-affected communities.

Another member of the team, Simon Mead, told Cosmos the motivation for ongoing research relates to CJD.

“Specifically from the perspective of the Medical Research Council (UK) the interest came from the fact that we were in the midst of the variant CJD outbreak in the UK, which was an orally transmitted prion disease. Kuru was the only other example of a disease transmitted in this way. The overarching idea therefore was to see what might be learned for future prion disease epidemics from studying the only example of a completed oral prion disease epidemic.”

Blood samples were taken from 4,217 individuals from communities in EHPNG by members of PNGIMR. Information was obtained about the individual’s village of residence, language spoken in that village, and the sex of the individual.

Participation of the communities involved was established and maintained through discussions with village leaders, communities, families, and individuals. The field studies followed the principles and practice of the PNGIMR, which included individual oral consent from all participants before any samples were obtained.

After filtering, there remained genetic samples from 943 people belonging to 21 linguistic groups.

The outcome of DNA analysis showed the genetic differentiation between linguistic groups in the region was “strikingly high.”

The paper says: “Our analyses reveal the presence of complex population structure even at dialect and village level. While of interest for understanding the origins of modern populations, these findings also provide the background for study of the genetic impact of the large-scale prion disease epidemic, kuru.”

“Overall our results demonstrate that simplistic descriptions of the population structure in regions like EHPNG based on linguistic groupings presumed to be static are likely to neglect the far richer texture of dynamic forces and history that has shaped communities.”

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