Ancient Tuberculosis in the Americas
For my Ph.D., I studied the evolutionary history of tuberculosis (TB) in the Americas. TB has afflicted humans for thousands of years, and today, it is the second-most common cause of death due to an infectious agent.
For a long time, the origins of TB in humans, especially in the Americas, were a topic of debate. Skeletal evidence suggests that TB was present in the Americas long before the arrival of Europeans in the late 15th century. But Europeans brought more virulent and transmissible TB strains along with them, which seem to have completely replaced the pre-existing American TB strains. Thus, we did not know what kind of TB strains were present in the pre-contact era Americas.
In 2014, the Stone Lab co-published the first ancient TB genomes (Bos et al. 2014). These TB genomes were recovered from the skeletal remains of people living in the coastal areas of Peru about 1,000-1,200 years ago. Surprisingly, these ancient TB strains were related to strains that today infect pinnipeds (such as seals and sea lions), suggesting that TB was introduced to the Americas via zoonotic transmission from marine mammals. Archaeological evidence tells us that the people living in the coastal regions of South America hunted seals for their meat and fur, which would have provided opportunities for TB transmission.
Questions remained as to how far did these seal TB strains spread. Did the seal TB variant infect people who were directly in contact with infected seals? Or did it also spread further inland and infect people living in the non-coastal regions?
Recently, I co-led a study to recover ancient TB genomes from human individuals living in the inland regions of Peru and Colombia, prior to the arrival of Europeans (Vågene et al. 2022). We found that similar seal TB strains were present in these inland individuals, despite them not having any direct contact with marine mammals or their remains. This suggests that the seal TB variant was carried via either the animal life or through human-to-human transmission to these inland peoples.
Currently, I am interested in studying what types of TB strains were present in pre-contact era North American individuals.
Check out our Behind The Paper blog post describing our findings related to ancient tuberculosis in the Americas.