Spanish
The latest advances in ancient DNA analysis sometimes require rewriting History: a study has just dismantled the idea that Europeans brought leprosy to America by finding genetic samples from individuals in Argentina and Canada who suffered from this disease centuries before the European arrival.
Leprosy is a disease that continues to affect thousands of people worldwide. Approximately 200,000 new cases are registered each year.
Until 2008, it was thought that the bacterium 'Mycobacterium leprae' was solely responsible for the disease, but that year another species that also caused it was found, 'Mycobacterium lepromatosis', identified in a Mexican patient in the United States and, subsequently, in red squirrels in the United Kingdom in 2016.
Now, a study conducted by scientists from the Pasteur Institute, the French national center for scientific research (CNRS) and the University of Colorado (USA), in collaboration with indigenous communities and more than 40 international researchers, including archaeologists, states that it was this new bacterium found in 2008 that was responsible for the first infections in America centuries before the Europeans arrived.
The study, described this Thursday in the journal Science, has been based on the analysis of DNA from nearly 800 samples, including ancient human remains (from archaeological excavations) and recent clinical cases that presented symptoms of leprosy.
"This discovery transforms our understanding of the history of leprosy in America, by demonstrating that there was a version of the disease that was already endemic among native populations before the arrival of Europeans," says one of the authors, Maria Lopopolo, a researcher at the Microbial Paleogenomics Laboratory of the Pasteur Institute in a statement from the center.
A Very Traveling Disease
Researchers have used advanced genetic techniques to reconstruct the genomes of the 'Mycobacterium leprae' bacteria from individuals found in Canada and Argentina.
The results show that the ancient strains of the bacteria, dating from similar periods in both cases (approximately 1,000 years ago), were very similar from a genetic point of view despite the distance. And, for the researchers, it is an indication that the pathogen spread rapidly throughout the American continent in just a few centuries.
You may be interested in: Cases of leprosy in wild chimpanzees confirmed
Scientists also identified several new lineages of the bacteria, including an ancestral branch that, despite having diverged from known species over 9,000 years ago, continues to infect humans today in North America, which would suggest an ancient and enduring diversification of the bacteria on the continent.The analyses reveal that the strains found in red squirrels in the United Kingdom in 2016 are part of an American lineage that was introduced to the British Isles in the 19th century, where it subsequently spread.
"This study 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," notes another of the authors, Nicolas Rascovan, also at the Pasteur Institute.
Researchers emphasize that this research project has been carried out in close collaboration with indigenous communities, who participated in the decisions regarding the use of ancestral remains and the interpretation of the results.
The ancient DNA and remaining materials were returned when requested, and the generated data was shared through ethical and adaptable platforms designed to enable data sharing that meets the specific expectations of each community.
