One of the greatest mysteries in the history of epidemics is whether or not syphilis was introduced into Europe after Columbus’ first voyage to the Americas. A recent study has confirmed the presence of one of the treponematosis diseases, called bejel, a syphilis-like disease, in South America at least 1000 years before the arrival of Columbus. This finding indicates that the bacterial family responsible for these diseases had already disseminated prior to the European expeditions of the 15th and 16th centuries.
An international study, published in the journal Nature, reveals that the oldest known genome of the Treponema pallidum, the bacterium responsible for treponematosis, has been identified in prehistoric human remains found in Brazil. This study was conducted by researchers from the Universitat de València and the Foundation for the Promotion of Health and Biomedical Research (FISABIO) of the Valencian Department of Health. The project, led by the University of Basel, the University of Zurich and the ETH Zurich polytechnic school in Switzerland, aims to clarify the origins of treponematosis, a group of infectious diseases caused by the T. pallidum bacteria.
Although endemic forms such as yaws and bejel are limited to developing countries, syphilis remains a global health issue. Infections have resurfaced in recent years and are proving to be largely resistant to azithromycin, which is used as an alternative treatment to penicillin, resulting in significant public health consequences.
This study analysed four bacterial genomes obtained from approximately 2000-year-old human remains found on a funeral mound in the Santa Catalina region of Brazil.
Archeogenetics
Until now, the identification of bacterial species responsible for serious infections and epidemics in the past has largely relied on evidence from collected bone samples. Recent advances in ancient DNA study methods, such as the one used in this study, allow for both the reconstruction of ancient genomes and the identification of the specific subspecies causing the infection. Surprising discoveries, like the identification of a prehistoric bejel agent in an American coastal environment, highlight the potential of the study of ancient DNA beyond inferences based on genomes of modern pathogens or purely archaeological interpretations.
Discoveries like this one demonstrate the study of ancient DNA’s potential to advance our knowledge of modern pathogens. Analysis of one of the infection agents found in Brazil reveals a striking resemblance to modern strains of bejel (T. pallidum endemicum). This suggests that this subspecies has remained largely unchanged to the present day.
Ancient genomes that speak to the present
“Although the exact timing of these events cannot be pinpointed, our analysis clarifies how these pathogens must have evolved, as bacteria are capable of transferring genes from one to another, through horizontal gene transfer or recombination, therefore affecting their structure. This information helps us to understand the contact between different subspecies of the same treponemal bacteria and their evolutionary path,” explains Marta Pla Díaz, one of the study’s primary authors, a PhD student at the FISABIO Foundation and the Universitat de València, who is now a postdoctoral researcher at the University of Basel.
In her doctoral thesis, Pla Díaz developed methods for analysing evolutionary processes, such as selection, recombination and horizontal gene transfer, in ancient and modern bacterial genomes, which involved analysing complex data such as those included in this study.
According to Fernando González Candelas, a professor at the UV and a primary author of the study, “it is crucial to include ancient genomes in the analysis to understand the factors and evolutionary processes involved in the past. This is particularly important in the case of T. pallidum, as it can shed light on how, when, and hopefully where the emergence of a new pathogen occurred, resulting in a pandemic as severe as that of syphilis in the last five centuries.” Pla Díaz and González Candelas are researchers from the Institute for Integrative Systems Biology (I2SysBio), a joint centre of the CSIC and the Universitat de València.
The research is advancing and the estimates are improving, bringing the researchers closer to their goal of uncovering the origins of syphilis. González Candelas, who also acted as Pla Diaz’s thesis supervisor, states that “while the origins of treponemal diseases are still unknown, this study confirms that these diseases were not foreign to the native inhabitants of America, who lived and died centuries before the first European explorers arrived on the continent.”
