Recent scientific findings have fundamentally altered our understanding of the history and origins of leprosy, or Hansen's disease, in the Americas. For many years, it was widely believed that leprosy arrived in the New World exclusively through European explorers and settlers who carried the bacterium Mycobacterium leprae. However, new research led by scientists from the Institut Pasteur in Paris, in collaboration with the French National Centre for Scientific Research and the University of Colorado, has revealed the presence of a second bacterial species, Mycobacterium lepromatosis, that had infected Indigenous populations in the Americas long before European contact.
This breakthrough discovery challenges the long-held assumption that leprosy was introduced to the Americas solely by Europeans. Instead, it demonstrates that Mycobacterium lepromatosis had been endemic in the continents for over a millennium prior to European arrival. Dr. Maria Lopopolo, the lead author of the study and a researcher at the Laboratory of Microbial Paleogenomics at the Institut Pasteur, emphasized the significance of these findings. She stated that this discovery "transforms our understanding of the history of leprosy in America," revealing that the disease was already established among Indigenous peoples prior to European colonization.
The study originated from earlier findings of Mycobacterium lepromatosis in a Mexican patient in 2008 and in red squirrels in the British Isles in 2016. Building on these observations, the research team applied advanced genetic reconstruction techniques to analyze the genomes of Mycobacterium lepromatosis extracted from ancient human remains found in Argentina and Canada. This genetic analysis showed that the bacterial strains from these geographically distant regions were closely related on the Mycobacterium family tree, indicating that the bacterium had spread rapidly across both North and South America.
To conduct this comprehensive study, researchers collaborated extensively with Indigenous communities, archaeologists, and international research institutions. They examined more than 800 DNA samples taken from ancient human remains and contemporary medical cases exhibiting symptoms of leprosy. This large-scale genetic survey provided robust evidence that Mycobacterium lepromatosis was widespread throughout the Americas well before European contact, rewriting the timeline and narrative of the disease's origins in the New World.
Nicolás Rascovan, the lead author of the study at the Institut Pasteur, highlighted the broader implications of the discovery. He noted that the research "proves that human history can be changed" by uncovering new information about pathogens and their movements. Additionally, he suggested that there might be unknown animal reservoirs for Mycobacterium lepromatosis, pointing to the need for further investigation into how this bacterium has persisted and evolved over time.
Leprosy, caused by bacteria that affect the skin, nerves, and eyes, remains a public health concern in certain parts of the world today. According to the Centers for Disease Control and Prevention (CDC), approximately 225 people in the United States and 250,000 worldwide contract Hansen's disease annually. While it is a chronic infection, leprosy can be effectively treated with antibiotics, which help prevent the progression of symptoms and transmission of the disease.
This groundbreaking study not only reshapes the historical understanding of leprosy but also underscores the importance of integrating genetic and archaeological research with the perspectives and cooperation of Indigenous communities. Such interdisciplinary approaches can illuminate hidden chapters of human and microbial history and provide insights that may inform current public health strategies.
In summary, the discovery of Mycobacterium lepromatosis as an ancient and endemic cause of leprosy in the Americas challenges previous beliefs that the disease was introduced solely by Europeans. Instead, it reveals that Indigenous populations were already affected by this bacterium for centuries before European explorers arrived. This finding, made possible through advanced genetic techniques and international collaboration, opens new avenues for research into the diversity, origins, and reservoirs of leprosy-causing bacteria, rewriting a significant part of the disease’s history in the New World.