Fernado González Candelas i Marta Pla.

One of the biggest mysteries in the history of epidemics is whether syphilis was introduced to Europe after Columbus's first voyage to the Americas. Now, a study has confirmed the presence of one of the treponematous diseases, called bejel (syphilis-like disease), in South America at least 1,000 years before Columbus arrived. Its existence suggests that the bacterial family that causes these diseases had already dispersed before the European expeditions of the 15th and 16th centuries.

In this international study, in which researchers from the University of Valencia and the Foundation for the Promotion of Health and Biomedical Research of the Valencian Community (Fisabio) participate, of the Ministry of Health, and published in the journal 'Nature', the oldest known genome of Treponema pallidum, the bacteria that causes treponematoses, has been identified in prehistoric human remains from Brazil. This work, led from Switzerland by the University of Basel, the University of Zurich and the ETH Zurich polytechnic school, contributes to clarifying the origin of this group of diseases. While endemic forms such as yaws and bejel tend to be limited to developing countries, syphilis persists as a global infection. These infections have re-emerged in recent years and mostly present resistance to azithromycin, which is used as an alternative treatment to penicillin with the consequent impact on public health.

The four bacterial genomes obtained and analyzed for this study were recovered from human remains approximately 2,000 years old, found in a burial hill in the Santa Catalina region, in Brazil.

Now, the identification of the bacterial species that caused serious infections and epidemics in the past has depended mainly on evidence in bone material samples. Currently, thanks to recent advances in methods for studying ancient DNA such as the one used in this study, it has been possible not only to reconstruct ancient genomes, but also to identify the specific subspecies that causes the infection. These surprising discoveries, such as the identification of a prehistoric bejel agent in a coastal American environment, highlight the potential of ancient DNA beyond inferences based on modern pathogen genomes or purely archaeological interpretations. This research demonstrates the potential of studying ancient DNA to advance knowledge about modern pathogens. So much so that, analyzing one of the infectious agents found in Brazil, it has been discovered that it bears such a close resemblance to modern strains of bejel (T. pallidum endemicum) that it seems that this subspecies has remained almost unchanged until today.

Ancient genomes that speak of the present

and helps us understand its evolutionary path,” explains Marta Pla Díaz, one of the first authors of the study and a doctoral student at the Fisabio Foundation and the University of Valencia, and now a postdoctoral fellow at the University of Basel. Valencia, Marta Pla developed methods to analyze evolutionary processes such as selection and recombination and horizontal gene transfer in ancient and modern bacterial genomes, which has facilitated the study of complex data such as those included in this study.

“The inclusion of ancient genomes in the analyzes is essential to understand what factors and evolutionary processes acted in the past and, in the case of T. pallidum, how, when, and hopefully where, they led to the appearance of a new pathogen causing a pandemic as serious as that of syphilis in the last five centuries.”, explains the professor at the University of Valencia Fernando González Candelas, who is also the director of Marta Pla's thesis. Both are also researchers at the Institute of Integrative Systems Biology (I2SysBio), a joint center of the CSIC and the University of Valencia. step closer. “The origin of syphilis is still unknown, but at least now we have no doubt that infections by treponema bacteria were not foreign to the inhabitants of America who lived and died centuries before the first European explorers arrived on this continent,” adds González Candelas, also a signatory of the article.