Ancient Tuberculosis in the Americas

Mycobacterial diseases, such as tuberculosis (TB) have long impacted humans, as well as our domesticated animals in the Old World. However, the origin of TB in the New World has been a long-standing topic of debate. Ample skeletal evidence for TB is present in pre-contact South and North America, but today New World TB is caused by Mycobacterium tuberculosis complex (MTBC) strains of European origin, suggesting that pre-existing MTBC strains were replaced following European contact. Previous research from our group led to the recovery of MTBC genomes from three 1000-year old skeletal TB cases from coastal Peru. The ancient Peruvian strains are distinct from any known human-adapted TB strain and are most closely related to strains adapted to sea mammals (specifically Southern Hemisphere pinnipeds). However, it remains unknown whether such pinniped-derived MTBC strains spread to inland parts of South America as well as North America by human-to-human transmission or whether different strains spread into North America via another route. The present work focuses on skeletal TB cases from pre-contact, protohistoric, and historic sites from Alaska, the Midwestern United States, and Colombia. DNA was extracted using a silica-based method and tested for presence of MTBC DNA using quantitative PCR assays. Fifteen DNA extracts tested positive for a region of the rpoB gene specific to the MTBC and the IS6110 and IS1081 repeat elements. In-solution target enrichment and sequencing of MTBC-specific genes showed good coverage as well as authenticated the presence of ancient DNA for these samples. Some of the samples that tested positive were enriched for the entire MTBC genome using an array-capture method and then sequenced. Analyses of these genomic data are currently ongoing.

This work was supported by funding from the National Science Foundation (BCS-1063939 and BCS- 1515163) and the Wenner-Gren Foundation.