They conducted a genetic study and discovered that Spaniards did not bring leprosy to America.

A genetic discovery has refuted one of the most widely held historical beliefs about one of the world's oldest diseases. A group of scientists has identified evidence that leprosy existed in the Americas long before European contact, contradicting the idea that it was the Spanish who brought the disease to the continent.

The discovery was based on the analysis of pre-Columbian human remains in which DNA fragments belonging to Mycobacterium lepromatosis , one of the two bacteria that cause this disease, were found. This strain was first identified in 2008 and, unlike Mycobacterium leprae , appears to have developed indigenously on the American continent.

The study, led by the Pasteur Institute and published in the journal Science , involved the collaboration of international experts in disease evolution. The samples analyzed, from both contemporary and ancient individuals, have identified three cases of leprosy prior to the arrival of Europeans in regions that now belong to Canada and Argentina.

The bacteria has been circulating for over a thousand years.

"Our interest began when we unexpectedly detected M. lepromatosis DNA in the remains of an ancient individual from North America," explained Nicolas Rascovan , a researcher at the Pasteur Institute. From that discovery, the team tracked down further cases that confirmed the presence of this bacteria at least 1,000 years ago .

The results also reveal the existence of ancient clades of this bacterium that have evolved independently for more than 9,000 years . This opens the door to the possibility of still-unknown animal reservoirs that have kept the disease active in certain regions.

In the United States, for example, cases of leprosy associated with armadillos have been documented. And in the United Kingdom, a similar strain has been detected in red squirrels, suggesting a much wider and more ancient distribution than previously thought.

The study also highlights that this variant, although less well-known, could represent an emerging threat if its spread dynamics differ from those of M. leprae. "Given its degree of diversity and expansion, M. lepromatosis could behave as an emerging pathogen," Rascovan noted.