In 1492, Columbus sailed the ocean blue, but when he sailed back 'cross the sea, he may have spread a new disease — syphilis.
The first recorded epidemic of syphilis happened during the Renaissance in 1495. Initially the plague broke out among the army of Charles the VIII after the French king invaded Naples. It then proceeded to devastate the continent.
"Syphilis was a major killer in Europe during the Renaissance," said researcher George Armelagos, a skeletal biologist at Emory University in Atlanta.
In the centuries since then, controversy has raged over whether Columbus and his men introduced not only the New World to Europe, but a new sexually transmitted disease as well. In the 20th century, critics of the "Columbian theory" proposed that syphilis had always bedeviled the Old World but simply had not been set apart from other rotting diseases such as leprosy until 1500 or so.
"This controversy has gotten pretty emotional," said researcher Kristin Harper, an evolutionary biologist at Emory. "Whenever you talk about a sexually transmitted disease and its origin, it seems like people want to blame some other country."
Caused by Treponema pallidum bacteria, syphilis is usually curable nowadays with antibiotics. Untreated, it can damage the heart, brain, eyes and bones and be fatal.
To see if Columbus and his men introduced syphilis to Europe after catching it in the Americas, scientists investigated the bacteria that cause syphilis and related ailments such as bejel and yaws, germs together known as treponemes. The research strategy focused on genetically comparing treponemes from across the globe to determine a family tree — which microbes gave rise to which — and perhaps thus see where syphilis came from.
After comparing 26 strains of treponemes from Africa, Europe, Asia, the Middle East, the Americas and the Pacific Islands, the researchers found the strains that caused the sexually transmitted disease originated recently, with their closest relatives being germs collected in South America. In other words, it seems to have come from the New World.
"The movement of diseases between Europeans and Native Americans is often seen as a one-way street, with Europeans bringing germs such as smallpox and measles," Harper said. "But syphilis seems to be an example of a disease that went the other way."
The researchers detail their findings Jan. 15 in the journal PLoS Neglected Tropical Diseases.
The disease that syphilis apparently originated from, yaws, is not sexually transmitted. Instead, yaws is spread by skin contact and is limited to hot and humid areas.
"One of the theories is that syphilis became venereally transmitted only when it reached Europe, where it was not as hot and humid as it was in the tropics, and where people wore more clothing, limiting ways it could spread," Harper told LiveScience. "Sex became its answer."
There are strains of yaws from the Old World. These seem to date back earlier on the family tree. Indeed, those Old World yaws strains were virtually indistinguishable from microbes that infect wild baboons. This suggests the progenitors of syphilis may have preyed upon our earliest ancestors. After these diseases migrated with humanity to the New World, Columbus and his men then imported syphilis back home, the new findings suggest.
However, "there are still a lot of questions left about the origin of syphilis," Harper said. And although molecular anthropologist Connie Mulligan at the University of Florida in Gainesville admired the genetic data from Harper and her colleagues, "I'm not sure you could make as strong a claim as they do based on this data for a New World origin for venereal syphilis."
Important to understand
Mulligan, who did not participate in this study, explained the genomes of treponemes might evolve differently than most others investigated to date.
"This means confirming any interpretations about their evolutionary history from the genetic material we have is much harder," she told LiveScience.
Harper noted that "if we can sequence the entire genomes of all of these strains of syphilis and its relatives, we might get enough information to get a better answer."
Understanding the evolution of syphilis "is important not just for biology, but for understanding social and political history," Armelagos said. "It could be argued that syphilis is one of the important early examples of globalization and disease, and globalization remains an important factor in emerging diseases."