New Research Reveals Ancient Origins of Leprosy in Americas

Leprosy, one of humanity’s oldest known diseases, has revealed a far more intricate history than previously understood. A groundbreaking study published in Science has uncovered DNA evidence showing that a species of leprosy-causing bacteria, Mycobacterium lepromatosis, was present in the Americas over 1,000 years ago—long before European colonization.

This discovery challenges the prevailing narrative that Europeans introduced leprosy to the New World. While Mycobacterium leprae, the more commonly known bacterium causing leprosy, was indeed brought by Europeans, M. lepromatosis appears to have evolved locally in the Americas for thousands of years.

The research team, led by Nicolas Rascovan of the Pasteur Institute, analyzed hundreds of DNA samples from both ancient remains and modern patients. They detected M. lepromatosis DNA in ancient individuals from regions now known as Canada and Argentina, confirming the bacteria’s presence across the continent centuries ago.

Leprosy, also known as Hansen’s disease, causes chronic infections affecting skin and nerve cells, potentially leading to severe disabilities if untreated. While antibiotics and improved sanitation have made the disease rare in many parts of the world, it remains a significant health issue in some regions, with over 200,000 cases reported globally each year.

Interestingly, the study identified multiple clades of M. lepromatosis, some evolving independently in the Americas for over 9,000 years. This suggests the bacteria may persist in unknown animal reservoirs, similar to how armadillos are linked to M. leprae infections in the U.S. The possibility of M. lepromatosis as an emerging pathogen with distinct dynamics raises new concerns for public health surveillance.

The research also hints at the transcontinental movement of M. lepromatosis, with evidence suggesting it was introduced to the British Isles in the 19th century, where it still infects red squirrels. However, the pathways by which it reached Asia remain unclear, underscoring the complexity of its global spread.

This evolving understanding of leprosy’s history not only reshapes scientific perspectives but also emphasizes the importance of continued research into neglected pathogens. Identifying animal reservoirs and tracking bacterial evolution are crucial steps toward controlling and preventing future outbreaks.

Why This Matters Today

Understanding the ancient origins and diverse evolution of leprosy-causing bacteria informs modern public health strategies. It highlights the need for vigilant monitoring of zoonotic reservoirs and emerging bacterial strains that could pose new threats. This knowledge can guide targeted interventions and improve diagnostic tools in affected regions.

In a world increasingly aware of infectious disease risks, the story of leprosy’s hidden history is a reminder that pathogens can evolve and spread in unexpected ways. It challenges us to rethink assumptions and invest in comprehensive research to protect global health.