Lepra existed in the United States long before the arrival of Europeans

LEPRA is a careless disease, mainly caused by bacteria Mycobacterium lepraeaffecting thousands of people around the world: approximately 200,000 new cases of leprosy each year are reported. Although M. Leprae It remains the main cause, this study focused on another species, Mycobacterium lepromatosisDiscovered in the United States in 2008 in a Mexican patient, and later in 2016 in red squirrels in the British islands. Directed by scientists from the Microbial Paleogenomic Laboratory in the Institut Pasteur, also associated with the CNR, and the University of Colorado, in collaboration with indigenous communities and more than 40 scientists from international institutions, including archaeologists, this study analyzed the DNA of almost 800 samples, including old human remains (of archaeological excavations) and recent clinical cases Leprosy Leprosy symptoms. The results confirm that M. lepromatosis It was already widespread in North and South America long before European colonization and provided information on the current genetic diversity of pathogenic mycobacteria.

“This discovery transforms our understanding of the history of LEPRA in the United States,” said Dr. Maria Lopopolo, first author of the study and researcher at the Microbial Paleogenomic Laboratory in the Institut Pasteur. “It shows that a form of disease was already endemic among indigenous populations long before Europeans came.”

The team used advanced genetic techniques to rebuild the genomes of M. lepromatosis of ancient individuals found in Canada and Argentina. Despite the geographical distance of several thousand kilometers, it was found that these old strains that date from similar periods (approximately 1,000 years ago) were surprisingly genetically close. Although they belong to two different branches in the evolutionary tree of the genre MycobacteriumThese branches are genetically closer to each other than any other known branch. This genetic proximity, combined with its geographical distance, necessarily implies a rapid spread of the pathogen throughout the continent, probably in just a few centuries.

The scientists also identified several new lineages, including an ancestral branch that, despite having diverted the rest of the diversity of known species more than 9,000 years ago, continues to infect humans today in North America, a discovery that suggests an ancient and lasting diversification in the continent, as well as a diversity to a large extent not explored that probably remains to be found.

In particular, the analyzes also suggest that the strains found in the red squirrels in the United Kingdom in 2016 are part of an American lineage that was introduced into the British islands in the 19th century, where it subsequently spread. This discovery highlights the recent ability of the pathogen to cross continents, probably through human or commercial exchanges.

“We are beginning to discover the diversity and global movements of this recently identified pathogen. The study allows us to raise the hypothesis that there could be reservoirs of unknown animals,” said Nicolás Rascovan, the main author of the study and head of the Microbial Paleogenomic Laboratory in the Institut Pasteur. “This study clearly illustrates how ancient and modern DNA can rewrite the history of a human pathogen and help us better understand the epidemiology of contemporary infectious diseases.”

The project was carried out in close collaboration with the indigenous communities, which participated in decisions on the use of ancestral remains and the interpretation of the results. The old DNA and the remaining materials were returned when requested, and the generated data were shared through ethical and adaptable platforms designed to allow the exchange of data that meet the specific expectations of indigenous communities.