Study: Leprosy Was Latent in Americas Long Before Colonization

Saba Yemen

03-06-2025

Washington - (Saba):
A recent scientific study has found that leprosy was latent in the Americas long before European colonization, contrary to the long-held belief that the disease was introduced by European settlers. This suggests that Native Americans had already been dying from the disease for centuries.
The primary cause of leprosy is known to be a bacterium called Mycobacterium leprae, and researchers still believe that Europeans introduced it to the Americas. However, a lesser-known cause appears to have been identified at that time.
The new study, conducted by an international team of researchers and published in the journal Science, found that another bacterium, Mycobacterium lepromatosis—a less common cause of leprosy—was present in the DNA of ancient human remains from Canada and Argentina dating back at least 1,000 years.
"This discovery changes our understanding of the history of leprosy in the Americas," says genomicist Maria Lopopolo of the Pasteur Institute in France. "It shows that a form of the disease was already endemic among indigenous populations long before the arrival of Europeans."
Mycobacterium leprae was first detected in a patient in the United States in 2008 and has since also been found in red squirrels (Sciurus vulgaris) in the United Kingdom. Researchers suggest it likely spread from the United States to the United Kingdom in the 19th century.
In collaboration with local indigenous communities, regarding the handling of ancestral remains, the researchers analyzed the DNA of a total of 389 ancient human samples and 408 modern human samples. Based on the results, they constructed a genetic family tree for the leprosy bacteria.
Although the ancient Canadian and Argentine samples were separated by thousands of kilometers, they were remarkably genetically similar. This suggests a rapid spread of leprosy across The Americas.
Based on the timeline compiled from DNA, the various strains of Mycobacterium leprae likely diverged from a common ancestor more than 9,000 years ago. With all these millennia of evolution, the team says there are likely more diverse forms of the bacteria still waiting to be discovered in the Americas.
"We are only just beginning to uncover the diversity and global movement of this newly discovered pathogen," says biologist Nicolas Rascovin of the Pasteur Institute. This study allows us to hypothesize the existence of unknown animal reservoirs for this virus.
All of this adds a valuable dimension to our understanding of the history of the Americas and of leprosy. It provides researchers with crucial data regarding the evolution and diversity of the disease.
Infectious diseases have played a significant role in the history of North, South, and Central America, with the arrival of Europeans bringing with them a range of new pathogens for which indigenous communities were biologically unprepared.
We now know that the leprosy aspect is more complex than previously thought. Around 200,000 new cases of the disease are reported globally each year, even though it is now treatable and curable with modern medicines.
'This study clearly demonstrates how ancient and modern DNA can rewrite the history of human pathogens and help us better understand the epidemiology of contemporary infectious diseases,' says Rascovan.
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