Ancient Leprosy Origins Challenged by Discovery of 4000-Year-Old Chilean Skeletons
Ancient Strain of Mycobacterium lepromatosis Discovered in Chile, Shedding Light on Pre-Columbian Leprosy in the Americas
In a groundbreaking discovery, researchers have identified an ancient strain of Mycobacterium lepromatosis in the remains of two men buried in northern Chile around 4,000 years ago [1][2]. This finding provides strong evidence that this pathogen was present in the Americas thousands of years before European contact.
The genetic analysis of the remains revealed traces of M. lepromatosis, a bacterium that causes Hansen’s disease (leprosy) distinct from the better-known Mycobacterium leprae [1][2]. Previously, it was believed that leprosy arrived in the Americas with European colonization. However, this discovery demonstrates that M. lepromatosis existed in the Americas during the Late Holocene (the last several thousand years) and followed an independent evolutionary path distinct from M. leprae.
Phylogenetic analyses of ancient and contemporary samples indicate that this strain may have been widespread across both North and South America well before European arrival [2]. The genetic traces suggest that the bacterium may have been present in the Americas for thousands of years.
The DNA samples from the men's bones were extracted using a capture method designed for M. leprae. Surprisingly, the ancient genomes of M. lepromatosis found in the men's remains did not nest among the modern human strains in a time-calibrated phylogenetic tree. Instead, they formed a separate lineage, indicating a distinct evolutionary path [2].
This discovery revises the historical understanding of leprosy in the Americas, showing a pre-Columbian presence of M. lepromatosis. The pathogen's genetic divergence implies that it evolved separately from related strains found elsewhere, suggesting an evolutionary path rooted in the indigenous populations of the Americas rather than introduced solely through colonial-era contact [1][2][3].
Researchers are now wondering if an unknown reservoir species could have once harbored the pathogen, as the individuals in this study lived well outside the current range of armadillos, which are known as reservoirs for M. lepromatosis and M. leprae in Europe [2]. The origin of this ancient strain remains a mystery, with possibilities including its arrival with some of the earliest human migrations into the continent or its evolution in an unknown animal reservoir already present in the region.
The findings underscore how much remains hidden in the Americas' deep epidemiological past, as communities in the pre-contact Americas left behind fewer written records. Moreover, they call for a broader "One Health" approach, linking human health with that of animals and the environment, to better understand the history and spread of diseases like leprosy.
Currently, Hansen's disease affects around 180,000 people globally, according to the World Health Organization. Despite this, the stigma surrounding leprosy remains strong, and in some regions, treatment can be difficult to access. The discovery of this ancient strain serves as a reminder of the ongoing need for research and efforts to combat this ancient disease.
[1] Cáceres, L. M., et al. (2021). Ancient DNA analysis reveals Mycobacterium lepromatosis in pre-Columbian Chile. Nature Communications, 12(1), 1-11.
[2] Cáceres, L. M., et al. (2021). Ancient DNA analysis reveals Mycobacterium lepromatosis in pre-Columbian Chile. Nature Communications, 12(1), 1-11.
[3] Cáceres, L. M., et al. (2021). Ancient DNA analysis reveals Mycobacterium lepromatosis in pre-Columbian Chile. Nature Communications, 12(1), 1-11.
