Early Human Migrations (ca. 13,000 Years Ago) or Postcontact Europeans for the Earliest Spread of Mycobacterium leprae and Mycobacterium lepromatosis to the Americas.

Samuel Mark

doi:10.1155/2017/6491606

Abstract

For over a century, it has been widely accepted that leprosy did not exist in the Americas before the arrival of Europeans. This proposition was based on a combination of historical, paleopathological, and representational studies. Further support came from molecular studies in 2005 and 2009 that four Mycobacterium leprae single-nucleotide polymorphisms (SNPs) and then 16 SNP subtypes correlated with general geographic regions, suggesting the M. leprae subtypes in the Americas were consistent with European strains. Shortly thereafter, a number of studies proposed that leprosy first came to the Americas with human migrations around 12,000 or 13,000 years ago. These studies are based primarily on subsequent molecular data, especially the discovery of a new leprosy species Mycobacterium lepromatosis and its close association with diffuse lepromatous leprosy, a severe, aggressive form of lepromatous leprosy, which is most common in Mexico and the Caribbean Islands. A review of these and subsequent molecular data finds no evidence for either leprosy species in the Americas before the arrival of Europeans, and strains of both species of leprosy found in eastern Mexico, Caribbean Islands, and Brazil came from Europe while strains found in western Mexico are consistent with their arrival via direct voyages from the Philippines.

Highlights

The proposition that leprosy did not exist in the Americas before the arrival of Europeans has been widely accepted for well over a century [1,2,3,4,5,6,7,8]
If the M. lepromatosis did spread to the Americas from Europe during the postcontact period, the M. lepromatosis strains found in the Caribbean Islands, Brazil, and the Canadian patient should all be closest to the Scottish strain, and the strains on the West coast of Mexico, which are more likely to have come from Asia during postcontact times, should be closest to the Asian strains in Singapore and Myanmar
Based on the data presented above M. lepromatosis and M. leprae diverged from their most recent common ancestor about 13.9 million years ago when each acquired a new host, possibly different species of monkeys or apes or even a rodent vector

Summary

Introduction

The proposition that leprosy did not exist in the Americas before the arrival of Europeans has been widely accepted for well over a century [1,2,3,4,5,6,7,8]. Northern Europeans introduced a few small pockets of leprosy to North America, like New Brunswick, Canada, and later in the Midwestern United States, while migrant workers from China and India were later sources of leprosy These studies ( postcontact theory) have been based on a combination of historical, paleopathological, and representational data. A number of papers were published challenging this postcontact theory, and they are primarily based on additional molecular studies, especially the discovery of a new leprosy species, Mycobacterium lepromatosis While these studies present what appears as a viable argument for the spread of both species of leprosy to the Americas around 13,000 years ago, a review of the historic, paleopathological, and molecular data argues against such an early arrival. Interdisciplinary Perspectives on Infectious Diseases for either species with a modified postcontact theory being consistent with the present evidence

Support for an Asian Migration Theory

Review of These Data

Findings

Conclusion