Famed explorer Christopher Columbus and his crew unleashed the scourge of syphilis on Europe, a new genetic study suggests, though some experts say the data is not conclusive.
The research adds more fuel to a controversial debate on the origins of the devastating sexually transmitted disease that can cause blindness, mental illness, and death.
Europe's first-known venereal syphilis epidemic occurred during the years immediately following Columbus's return, fueling a long-held theory that the explorer carried the disease to the continent.
Study lead author Kristin Harper and colleagues compared genetic data from 26 strains of the treponema bacteria family—those responsible for venereal syphilis as well as nonvenereal forms of the disease—and closely related ailments such as yaws, a tropical bacterial infection.
The results showed that modern-day syphilis strains resembled those found in South America.
This New World origin for syphilis strongly supports the Columbus theory, said Harper, an evolutionary biologist at Atlanta's Emory University.
"We hope to find genetic differences we can use to build a family tree of these bacteria," she added. "In doing that we hope to get an idea of where and when syphilis evolved."
Incomplete Tale
Bones on each side of the Atlantic have yielded some tantalizing but inconclusive clues suggesting where and when the disease existed before Columbus's voyages.
Numerous pre-Columbian Old World remains appear to show signs of syphilis, including pitted skulls and unnaturally fat lower leg bones, some researchers say.
But few examples survive, and those that appear to show syphilis may in fact be evidence of other related viruses.
"Diagnosis of specific [syphilis-causing] diseases can be problematic in skeletal remains from archaeological sites, because they are often fragmentary and poorly preserved," said Charlotte Roberts, a bioarchaeologist at Durham University in the United Kingdom.
"Without the complete skeleton—or in the case of treponemal disease diagnosis, the skull and long bones—a specific diagnosis cannot be made with ease."
While some argue that Old World bones "proving" the existence of pre-Columbian syphilis are suspect, Roberts claims the same can be said of New World remains suggesting an American origin.
Connie Mulligan, a molecular anthropologist at the University of Florida, disagrees with Harper's conclusions—saying that the existing genetic data does not begin to answer that question.
"Opportunistic timing and the fact that [the voyage and European syphilis outbreak] are so closely tied has provided this interesting historical question: Did he bring it back to the Old World, or was it already present in the Old World?" Mulligan asked.
"We just don't know."
She also notes that at least one theory suggests there is no genetic difference at all between syphilis and its relative ailments.
"Is it just the same disease that has different manifestations in different climates?" she asked.
"That's what I think Harper's data might be showing. ... To me that is very interesting, almost more interesting than the single geographic origin of venereal syphilis.
"In that case, asking where venereal syphilis evolved is the wrong question."
Harper's study was published recently in the journal PLoS Neglected Tropical Diseases.
Tandem Evolution
Geneticist Spencer Wells is a National Geographic Society Explorer-in-Residence and director of the society's Genographic Project. (The National Geographic Society owns National Geographic News.)
He said Harper's study "basically says we need to do a lot more work and look at a lot more of the genome, more DNA, and more strains of syphilis from around the world."
The syphilis mystery also spotlights how infectious diseases and humans have genetically evolved in tandem over time, he added.
Yaws, which many scientists believe descended from syphilis, has likely been with humans since their origins in Africa.
"We probably carried it around the world with us," Wells said. "Over hundreds of thousands or even millions of years, you slowly start to adjust to each other so that the organism still causes a disease, but it doesn't cause a very bad disease."
"But something happened at some [recent] point that likely allowed it to develop into syphilis, and it took off as a new kind of disease that caused all kinds of problems."
Wells notes that the genetic study of such diseases can teach us a great deal about the way our own genes have evolved.
"We see clear evidence in our own genome of adaptations to disease," he said. "Recently people have started looking at the genomes of infectious diseases, and we tend to see overlap in those processes [of adaptation]."
The use of genetics to track the origins and movements of disease is a rapidly growing field.
But even Harper suggests that we may never be able to definitively identify the mysterious origins of syphilis and Columbus's possible role in its spread.
"The truth is I think we're never going to nail this thing—we just don't have the strains to do that," she said.
"We have to work with what we have, and we have an [incomplete] picture that we have to make the most of."
by news.nationalgeographic.com
