Leprosy Was Present in America Long Before European Arrival

Contrary to popular belief, the influence of leprosy existed among the American populace long before Europeans arrived.

“The narrative was that Europeans introduced this dreadful disease to America,” states Nicholas Lascovan from the Pasteur Institute in Paris. “Our findings challenge that notion.”

Globally, the majority of leprosy instances result from the bacteria Mycobacterium leprae. However, in 2008, Xiang-Yang Han and his team from the University of Texas MD Anderson Cancer Center identified a second causative agent, M. lepromatosis, in two individuals from Mexico afflicted with leprosy. Since then, more occurrences of this pathogen have been noted in the US, Canada, Brazil, and Cuba, as well as in four people from Singapore and Myanmar.

Driven to explore this less-studied pathogen, Lascovan collaborated with Han, other researchers, and indigenous communities to analyze ancient DNA from 389 individuals who lived in America before European contact.

They discovered M. lepromatosis at one archaeological site near the Alaska-Canada border and two locations along Argentina’s southeastern coastline, all carbon-dated to roughly 1,000 years ago. The bacterial genome exhibited slight variations, indicating a distinct strain separated by about 12,000 kilometers. “It has rapidly spread across the continent for centuries,” explains Lascovan.

DNA analysis from numerous modern cases, primarily in the US and Mexico, showed that nearly all contemporary strains are closely related, with minor variations from ancient times. Nonetheless, the team also recognized a rare and unusually ancient strain in modern populations that wasn’t found in archaeological sites, suggesting the existence of at least two distinct strains. Notably, M. lepromatosis is still present in North America today, alongside M. leprae, which was introduced by Europeans.

The findings imply that these bacteria have diverged and evolved within the United States for approximately 10,000 years. About 3,000 years ago, a lineage of the pathogen mutated into its current form, capable of infecting red squirrels in the UK and Ireland, causing issues such as skin swelling and unpleasant lesions.

Regarding their origins, genetic data indicate that M. lepromatosis and M. leprae diverged from a shared ancestor over 700,000 years ago, yet the precise location of this divergence remains unidentified.

Modern cases of M. lepromatosis appear to primarily affect the blood vessels of the feet, while M. leprae targets nerves, according to Han. Those infected with M. lepromatosis may experience blocked blood flow, tissue death, and skin breakdown, leading to potentially fatal complications from severe secondary infections caused by bacteria like Staphylococcus aureus. The disease can also progress to internal organs such as the liver and spleen, resulting in some individuals succumbing before the skeletal system exhibits leprosy signs.

This may help clarify why archaeologists have not identified leprosy in ancient artifacts from the Americas, as Han mentions. While skeletal remains from Europe and Asia frequently show clear signs of leprosy-related bone damage, the ancient Canadian individuals examined in this study exhibited only ambiguous jaw lesions, which could arise from various conditions.

Annemieke Geluk from Leiden University in the Netherlands remarked that this “remarkable study” necessitates a rethink of the disease’s history. “My teaching materials indicate that there was no leprosy in the Americas before European colonization,” she noted, “I will need to revise my materials!”

Beyond its historical implications, this research also highlights pressing public health concerns. Leprosy is resurging in certain global regions, and rising antibiotic resistance complicates treatment. “Understanding this is highly critical,” says Geluk. “We need collaborative efforts worldwide to map existing strains.”