According to popular belief, the sailors around Christopher Columbus brought syphilis to Europe. Because shortly after their return from the New World, the first major epidemic of this sexually transmitted disease raged on our continent. But DNA analyzes of old skeletons are now calling this assumption into question. They show that a young person in Estonia suffered from syphilis as early as the middle of the 15th century – well before Columbus and his team returned. In addition, the analyzes show that two other diseases caused by closely related pathogens were bypassed in Europe.
Today syphilis is a venereal disease that is widespread almost all over the world and affects millions of people every year. The infection caused by the bacterium Treponema pallidum pallidum is mainly transmitted through unprotected sex, but can also be passed on through blood transfusions or from the mother to her unborn child. If left untreated, the pathogen initially triggers small pustules and ulcers, but in the later stages it can also affect joints, bones, internal organs and the brain. However, especially in the early stages, the infection can be treated well with antibiotics. It has long been known from historical records that syphilis has existed in Europe for centuries. The earliest known epidemic began in 1495 after a Franco-Italian war and is spreading rapidly across half of Europe.
DNA test on centuries-old bones
“Because this first European outbreak coincided with the first expeditions to America, the theory arose that syphilis was brought to Europe by the return of Columbus and his crew from the New World in 1493,” explains Kerttu Majander from the University of Zurich and their colleagues. Other theories assume that the syphilis pathogen was already present in Europe – due to a lack of evidence, however, this could not be proven. A few years ago, archaeologists found a skeleton from the 14th century in Austria with bone changes typical of syphilis. But because other diseases can trigger similar changes and there was no genetic evidence of the pathogen, this early case of syphilis was controversial. The origin of the “lust epidemic” therefore remained in the dark.
In the meantime, however, the extraction and analysis of ancient DNA from historical remains has made great strides. Majander and her colleagues have now used these techniques to examine the genetic material from nine dead buried in Northern and Central Europe from the 15th to the 18th centuries for traces of the DNA of Treponema bacteria. They found what they were looking for in four of these samples – two from Finland, one from Estonia and one from the Netherlands. Comparative analyzes of the genetic make-up of the pathogen showed that one of the dead suffered from yaws, an infection with the Treponema pallidum pertenue bacterium that is now only widespread in the tropics. However, two of the samples, one from the mid-15th century and one from the 17th century, showed traces of the syphilis pathogen. “These genomes represent the first molecular evidence of this Treponema subspecies in early modern Europe,” say the scientists.
Syphilis was rampant even before Columbus returned
The evidence of the syphilis pathogen in a European skeleton from the mid-15th century shows that syphilis was present in Europe even before Columbus returned. “Our dates place the first infection through syphilis before the first contact with the New World and suggest that the causative agent of the great, continent-wide epidemic at the end of the 15th century was already present in the Old World,” say Majander and her colleagues . This does not contradict the assumption that the sea voyages to the New World brought new strains of Treponema pallidum into Europe. Nevertheless, syphilis and its pathogen were already present in Europe before. Together with the yaw bosom, these endemic pathogen variants seem to have spread mainly in northern Europe at that time.
And the research team discovered something else: In addition to syphilis and yaws, there was apparently another Treponema subspecies in Europe. Majander and her team found their gene signature in the DNA samples of the skeleton buried in the Netherlands in the 17th century. “This unforeseen find is extremely exciting for us because this previously unknown sister line has genetic similarity to all modern Treponema subspecies,” says Majander. Based on their genetic comparisons, she and her colleagues assume that this strain is a common precursor of yaws and another Treponema disease that exists today. Accordingly, several Treponema subspecies circulated in parallel in the European population of the late Middle Ages and the Renaissance. “The different treponematoses could have developed together and exchanged genetic material before or during intercontinental contacts,” says Majander’s colleague Verena Schünemann. However, whether and how this happened is still unclear.
Source: Kerttu Majander (University of Zurich) et al., Current Biology, doi: 10.1016 / j.cub.2020.07.058