DNA analysis of early plague victims pinpoints Black Death’s start on Silk Road trading communities in mountain region of what is now modern-day Kyrgyzstan in Central Asia
Microbiologists and clinical laboratory scientists will likely find it fascinating that an international team of scientists may have solved one of history’s greatest mysteries—the origin of the bubonic plague that ravaged Afro-Eurasia in the mid fourteenth century. Also known as the Black Death, the plague killed 60% of the population of Europe, Asia, and North Africa between 1346-1353 and, until now, the original source of this disease has largely gone unsolved.
In their study published in the journal Nature, titled, “The Source of the Black Death in Fourteenth-Century Central Eurasia,” the authors outlined their investigation of cemeteries in the Chüy Valley of modern-day Kyrgyzstan. The tombstone inscriptions showed a disproportionally high number of burials dating between 1338 and 1339 with inscriptions stating “pestilence” as the cause of death.
Big Bang of Plague
Using 30 skeletons that were excavated from these cemeteries in the late 1880s and moved to St. Petersburg, Russia, the scientists analyzed the DNA of ancient pathogens recovered from the remains of seven people. They discovered Yersinia pestis (Y. pestis) DNA in three burials from Kara-Djigach, which lies in the foothills of the Tian Shan mountains.
According to another article in Nature, the scientists showed that a pair of full Y. pestis genomes from their data were direct ancestors of strains linked to the Black Death, and that the Kara-Djigach strain was an ancestor of the vast majority of Y. pestis lineages circulating today.
“It was like a big bang of plague,” Krause stated at a press briefing, Nature reported.
The research team concluded that the Tian Shan region was the location where Y. pestis first spread from rodents to people, and that the local marmot colonies likely the prevalent rodent carriers of plague.
“We found that modern strains [of the plague] most closely related to the ancient strain are today found in plague reservoirs around the Tian Shan mountains, so very close to where the ancient strain was found. This points to an origin of Black Death’s ancestor in Central Asia,” Krause explained in a Max Planck Institute news release.
He told Nature that fleas likely passed the marmot-based infection on to humans, sparking a local Kyrgyzstan epidemic. The disease then spread along the Silk Road trade routes, eventually reaching Europe, where rats (and the fleas that they carried) spread the disease.
Understanding Context of Plague
Writing in The Conversation, Associate Professor of Medieval and Environmental History Philip Slavin, PhD, University of Stirling, who co-authored the study, explained that Kara-Djigach is unlikely to be “the specific source of the pandemic,” but rather that the “disaster started somewhere in the wider Tian Shan area, perhaps not too far from that site,” where marmot colonies were likely the source of the 1338-1339 outbreak.
Making a modern-day comparison, Krause told Nature, “It is like finding the place where all the strains come together, like with coronavirus where we have Alpha, Delta, Omicron all coming from this strain in Wuhan.”
Slavin maintains that understanding the “big evolutionary picture” is key when studying the phenomenon of emerging epidemic diseases.
“It is important to see how these diseases develop evolutionary and historically, and avoid treating different strains as isolated phenomena,” he wrote in The Conversation. “To understand how the diseases develop and get transmitted, it is also crucial to consider the environmental and socioeconomic contexts.”
Scientists have spent centuries debating the source of the Black Death that devastated the medieval world. The multidisciplinary process used by the Slavin/Krause-led team provides a lesson to clinical laboratory managers and pathologists on the important role they play when collaborating with colleagues from different fields on scientific investigations.
For blood brothers Quest and LabCorp this is good news, since the two medical laboratory companies perform most of the testing for the biggest DTC genetic test developers
Should clinical laboratories be concerned about direct-to-consumer (DTC) genetic tests? Despite alerts from healthcare organizations about the accuracy of DTC genetic testing—as well as calls from privacy organizations to give DTC customers more control over the use of their genetic data—millions of people have already taken DTC tests to learn about their genetic ancestry. And millions more are expected to send samples of their saliva to commercial DTC companies in the near future.
This growing demand for at-home DTC tests does not appear to be subsiding. And since most of the genetic testing is completed by the two largest lab companies—Quest Diagnostics (NYSE:DGX) and Laboratory Corporation of America (NYSE:LH)—other medical laboratories have yet to find their niche in the DTC industry.
Another factor is the recent FDA authorization allowing DTC company 23andme to report the results of its pharmacogenetic (PGx) test directly to customers without requiring a doctor’s order. For these reasons, this trend looks to be gaining momentum and support from federal governing organizations.
Dark Daily has
reported on DTC genetic
testing for many years. According to MIT’s Technology Review, 26 million people—roughly
8% of the US population—have already taken at-home DNA tests. And that number
is expected to balloon to more than 100 million in the next 24 months!
“The genetic genie is out of the bottle. And it’s not going
back,” Technology Review reports.
The vast majority of the genetic information gathered goes into the databases of just four companies, with the top two—Ancestry and 23andMe—leading by a wide margin. The other two major players are FamilyTreeDNA and MyHeritage, however, Ancestry and 23andMe have heavily invested in online and television advertising, which is paying off.
As more people add their data to a given database, the likelihood they will find connections within that database increases. This is called the Network Effect (aka, demand-side economies of scale) and social media platforms grow in a similar manner. Because Ancestry and 23andMe have massive databases, they have more information and can make more connections for their customers. This has made it increasingly difficult for other companies to compete.
Quest Diagnostics and LabCorp do the actual gene sequencing
for the top players in the DTC genetic testing sector. The expected wave of new
DTC genetic test costumers (74 million in the next 24 months) will certainly
have a beneficial revenue impact on those two lab companies.
Why the Explosion in Genetic
Testing by Consumers?
In 2013, just over 100,000 people took tests to have their
DNA analyzed, mostly using Ancestry’s test, as Dark Daily reported. By 2017, that
number had risen to around 12 million, and though Ancestry still had the
majority market share, 23andMe was clearly becoming a force in the industry,
noted Technology Review.
And now there are several health-related reasons as well. For
example, the study of pharmacogenetics has led clinicians to understand that
certain genes reveal how our bodies process some medications. The FDA’s clearance
allows 23andMe to directly inform customers about “genetic variants that may be
associated with a patient’s ability to metabolize some medications to help
inform discussions with a healthcare provider. The FDA is authorizing the test
to detect 33 variants for multiple genes,” the FDA’s press
Controversy Over DTC
The use of DTC genetic tests for healthcare purposes is not without scrutiny by regulatory agencies. The FDA removed 23andMe’s original health test from the market in 2013. According to Technology Review, the FDA’s letter was “one of the angriest ever sent to a private company” and said “that the company’s gene predictions were inaccurate and dangerous for those who might not fully understand the results.”
23andMe continues to refine its DTC tests. However, the debate continues. In February of this year, the New York Times (NYT) editorial board published an op-ed warning consumers to be wary of health tests offered by 23andMe, saying the tests “look for only a handful of [genetic] errors that may or may not elevate your risk of developing the disease in question. And they don’t factor into their final analysis other information, like family history.”
Anne Wojcicki, CEO and co-founder of 23andMe, responded with her own op-ed to the NYT, titled, “23andMe Responds: Empowering Consumers.” In her letter, Wojcicki contends that people should be empowered to take control of their own health, and that 23andMe allows them to do just that. “While 23andMe is not a diagnostic test for individuals with a strong family history of disease, it is a powerful and accurate screening tool that allows people to learn about themselves and some for the most common clinically useful genetic conditions,” she wrote.
Nevertheless, privacy concerns remain:
Who owns the results, the company or the
Who can access them?
What happens to them a year or five years after
the test is taken?
When they are sold or used, are consumers
Even as experts question the accuracy of DTC genetic testing
in a healthcare context, and privacy concerns continue to grow, more people
each year are ordering the tests. With predictions of 74 million more tests
expected in the next 24 months, it’s certain that the medical laboratories that
process those tests will benefit.
Portable devices have potential to analyze DNA and produce results in the field in minutes to hours, eliminating the need to return to a medical laboratory to analyze samples
Pathologists continue to hear about research efforts to create small devices that can perform DNA analysis. In the past year, four research organizations, including one in the United States, one in New Zealand, and two in the U.K., have unveiled several devices that will analyze DNA in the field.
This line of research is of particular interest in developing countries where resources such as electricity for refrigeration are scarce. Some of the DNA testing devices will produce results in minutes to hours, eliminating the need to return to a clinical laboratory to analyze samples.
Mobile Medical Laboratory Designed to Fit in a Pocket(more…)