Leprosy of the feet (Credit: UCL)
In the arid, windswept valleys of Northern Chile, two ancient skeletons are revolutionizing scientists’ understanding of a disease with significant medical and cultural implications. Interred for 4,000 years, these bones yielded a surprising discovery: preserved genetic traces of Mycobacterium lepromatosis, one of the two bacteria responsible for Hansen’s disease, also known as leprosy.
While Hansen’s disease is now a rare and treatable condition, its historical origins are far from straightforward. The unearthing of this ancient strain of M. lepromatosis unveils a new chapter in the disease’s narrative. Previously assumed to have arrived in the Americas during European colonization, leprosy may have been a part of the continent’s history much earlier than previously thought.
This groundbreaking evidence extends the timeline of M. lepromatosis’s presence in the Americas by millennia and indicates a distinct evolutionary trajectory for this form of the disease, separate from its more well-known counterpart, Mycobacterium leprae, which likely evolved in Eurasia.
New genetic revelations shed light on ancient leprosy in Chile, transforming our understanding of Hansen’s disease in the Americas. (Credit: Oscar Eduardo Fontana-Silva & Anna Brizuela)
An Ancient Disease with Divergent Paths
For years, researchers have focused on M. leprae, the predominant leprosy bacterium, tracing its origins to Eurasia, where it likely emerged around 7,000 years ago during the Neolithic era. This period also saw the emergence of other major infectious diseases like plague, tuberculosis, and typhoid fever. Over time, M. leprae spread to Europe, Asia, and Oceania, with skeletal markers, such as bone deformities, appearing in archaeological remains dating back 5,000 years.
On the other hand, M. lepromatosis, a more recently identified bacterium, has remained enigmatic. It causes severe forms of Hansen’s disease, including diffuse lepromatous leprosy and the life-threatening Lucio’s phenomenon. Unlike M. leprae, which is well-documented in historical records and archaeological samples, M. lepromatosis had never been recovered from ancient remains until now.
A collaborative research team led by Kirsten Bos at the Max Planck Institute for Evolutionary Anthropology, in conjunction with scientists from Argentina and Chile, unearthed the bacterium’s DNA in two remarkably preserved adult male skeletons from the archaeological sites of El Cerrito and La Herradura in Chile. This discovery marks the first time that a complete ancient genome of M. lepromatosis has been reconstructed and analyzed.
“This uncovering of ancient DNA is reshaping our existing knowledge,” remarks Bos, who heads the institute’s Molecular Paleopathology group. “The advanced techniques now available for studying ancient pathogen DNA enable us to delve into unexpected diseases
Doctoral candidate DarÃo Ramirez, from the University of Córdoba in Argentina, is conducting research on pathological bone samples in the ancient DNA facility at the Max Planck Institute for Evolutionary Anthropology. Initially suspicious due to leprosy being historically considered a colonial-era disease, Ramirez was the first to identify genetic traces of leprosy in the bones. Further analysis revealed that the DNA belonged to M. lepromatosis rather than M. leprae, challenging previous assumptions.
The team’s findings suggest that the M. lepromatosis lineage may have existed in the Americas for thousands of years, evolving separately from its Eurasian counterpart. This discovery hints at a distinct history for M. lepromatosis and M. leprae, despite both being pathogens causing Hansen’s Disease.
Prior to European contact, various human communities inhabited the Americas for millennia, adapting to diverse climates and environments. While archaeological studies have provided glimpses of pre-contact disease presence, the discovery of ancient M. lepromatosis DNA sheds light on leprosy’s early existence in South America.
Anthropology professor Rodrigo Nores anticipates further discoveries related to the disease’s ancient presence in the Americas, such as its occurrence in Chile around 4000 years ago. Understanding the historical spread and impact of leprosy could help destigmatize the disease and raise awareness, especially in regions with uneven access to treatment.
The research also raises questions about the origins and transmission of M. lepromatosis, as it has been detected in rare cases, including wild squirrels in the UK and Ireland. The absence of known animal hosts in the Americas distinguishes M. lepromatosis from M. leprae, which infects armadillos.
Although initial evidence points towards an American origin for M. lepromatosis, more genomic data is required for definitive conclusions. This study underscores the value of ancient DNA research in uncovering the mysteries of past diseases and highlights the potential of genomics in deepening our understanding of pathogens.
Bos mentions that M. lepromatosis has a significant historical presence in the Americas. Further examination of ancient remains is anticipated to reveal additional information about the origin, distribution, and impact of the disease on past populations. The research findings can be accessed on the internet in the journal Nature Ecology & Evolution. Please note that the article was originally published by The Brighter Side of News. Interested in more uplifting stories like this? Subscribe to The Brighter Side of News newsletter.
