Periodic Reporting for period 3 - CoDisEASe (Communicable Disease in the Age of Seafaring)
Berichtszeitraum: 2021-12-01 bis 2023-05-31
The CoDisEASe (Communicable Disease Exchange in the Age of Seafaring) project aims to explore various aspects of infectious disease transmission in historical populations through the study of ancient DNA. Molecular signatures of various pathogens can preserve in archaeological tissues, and scientific techniques have now matured to the point where ancient diseases can be studied at the genomic level. CoDisEASe aims to draw upon novel developments in the retrieval of ancient molecules to study genetic changes in infectious diseases on a broad geographic scale that will also take us deep into our evolutionary past. Archaeological human remains from the medieval and post-medieval periods will feature most prominently in the project, as contacts between world populations (and exchange of their infectious diseases) are likely to have become more frequent with advances in naval technology and more extensive contact between human groups. To complement the intended work on infectious disease movements and their evolution, we will also investigate human genes involved in immune function to better understand how disease burdens have influenced our genetic make-up over time.
Work toward the goals of the grant has primarily focused on securing access to archaeological samples for use in pathogen screening and evaluation of immune gene variation. Archaeological human remains have been obtained from several European countries including Belgium, Spain, Germany, Lithuania, and Poland, and also from American countries such as Peru, Chile, Mexico, and Antigua and Barbuda. The human remains are being processed by doctoral students and postdoctoral researchers employed by the grant. Through keen eyes and diligent pathogen screening, the team is happy to report on the discovery of a yaws infection in medieval Europe. Though this disease, which is similar to syphilis, is present today in tropical regions, we identified it in a woman from 15th century Lithuania. The yaws genome we reconstructed enabled us to demonstrate that yaws, as we know it today, is much younger than previously thought, and likely emerged only within the last 1000 years. Its presence in a person from the Baltic region also suggests that it was endemic in Europe, and hence must have spread very quickly after it first appeared in its presumed tropical place of origin. In the future work made possible through this grant, we hope to reveal the secrets of additional diseases through use of the unique resource of ancient pathogen genomes. We also look forward to linking disease transmission to changes in human immune function through the study of ancient human DNA in both European and American contexts.
Research in pursuit of the goals of this grant is made possible through use of cutting-edge techniques for both the retrieval of degraded ancient molecules and computational methods for their identification. Ancient DNA work poses many challenges: over the years, DNA molecules usually degrade into small fragments which can be chemically damaged, and those remaining trace amounts can be obscured when bacteria from the soil or the environment dominate in archaeological samples. These factors make it difficult to distinguish environmental microbes from those that were present in the individual at the time of death. CoDisEASe makes use of updated laboratory methods to access bacterial DNA that has preserved for hundreds of years in archaeological tissues, and aims to identify the ancient pathogens represented amidst a noisy microbial background through use of the most robust and up to date methods of detection. With this approach we’re able to find and track infectious diseases on a scale never before possible, even for diseases that are unexpected in a given time period or location. We will evaluate the evolution of human immune function with similar rigour using powerful laboratory techniques catered to the recovery of immune genes from archaeological human remains. Concurrent investigation of both hosts and pathogens in our past offers incredible potential for understanding how evolutionary forces have shaped us over a prolonged time period.