日批在线视频_内射毛片内射国产夫妻_亚洲三级小视频_在线观看亚洲大片短视频_女性向h片资源在线观看_亚洲最大网

   

New study blames Columbus for syphilis spread

(Agencies)
Updated: 2008-01-17 08:26

CHICAGO - New genetic evidence supports the theory that Christopher Columbus brought syphilis to Europe from the New World, US researchers said Monday, reviving a centuries-old debate about the origins of the disease.

They said a genetic analysis of the syphilis family tree reveals that its closest relative was a South American cousin that causes yaws, an infection caused by a sub-species of the same bacteria.


Christopher Columbus in an undated image courtesy of the Library of Congress. New genetic evidence supports the theory that Columbus brought syphilis to Europe from the New World, US researchers said on Monday, reviving a centuries-old debate about the origins of the disease. [Agencies]

"Some people think it is a really ancient disease that our earliest human ancestors would have had. Other people think it came from the New World," said Kristin Harper, an evolutionary biologist at Emory University in Atlanta.

"What we found is that syphilis or a progenitor came from the New World to the Old World and this happened pretty recently in human history," said Harper, whose study appears in journal Public Library of Science Neglected Tropical Diseases.

She said the study lends credence to the "Columbian theory," which links the first recorded European syphilis epidemic in 1495 to the return of Columbus and his crew.

"When you put together our genetic data with that epidemic in Naples in 1495, that is pretty strong support for the Columbian hypothesis," she said.

Syphilis, a sexually transmitted disease caused by the bacterium Treponema pallidum, starts out as a sore, but progresses to a rash, fever, and eventually can cause blindness, paralysis and dementia.

Most recent evidence of its origins comes from skeletal remains found in both the New World and the Old World. Chronic syphilis can leave telltale lesions on bone. "It has a worm-eaten appearance," Harper said in a telephone interview.

SYPHILIS FAMILY TREE

Harper used an approach that examines the evolutionary relationships between organisms known as phylogenetics. She looked at 26 strains of Treponema, the family of bacteria that give rise to syphilis and related diseases like bejel and yaws, typically a childhood disease that is transmitted by skin-to-skin contact.

The study included two strains of yaws from remote areas of Guyana in South America that had never been sequenced before.

"We sequenced 21 different regions trying to find DNA changes between the strains," Harper said.

They concluded that while yaws is an ancient infection, venereal syphilis came about fairly recently. Harper suspects a nonvenereal subspecies of the tropical disease quickly evolved into venereal syphilis that could survive in the cooler, European climate.

But it is not clear how this took place. "All we can say is the ancestor of syphilis came from the New World, but what exactly it was like, we don't know," she said.

In a commentary published in the same journal, Connie Mulligan of the University of Florida and colleagues disagreed with Harper's analysis, suggesting her conclusions relied too heavily on genetic changes from the Guyana samples.

Mulligan suggested that better clues would come from DNA extracted from ancient bones or preserved tissues.

Harper concedes that more work needs to be done to explain the journey of syphilis to the New World. "This is a grainy photograph," she said.



Top World News  
Today's Top News  
Most Commented/Read Stories in 48 Hours
主站蜘蛛池模板: 精品国产乱码 | 香蕉视频在线免费播放 | 亚洲影视一区二区三区 | 国内三级视频 | 麻豆日韩| 午夜一区二区三区 | 国内精品免费视频 | 欧洲精品一区 | 亚洲欧美一区二区三区情侣bbw | 欧美精品国产 | 欧美影视一区二区三区 | 欧美亚洲国产精品 | 黄色小视频在线播放 | 欧美一区二区三区在线播放 | 一区二区视频在线免费观看 | 香蕉网久久 | 欧美性猛交xxxx| www.黄色网 | 激情婷婷六月 | 91成人亚洲 | 热热热热色 | 精品久久久久一区二区国产 | 欧日韩在线视频 | 久久亚洲精品小早川怜子66 | 在线观看毛片网站 | 黄色一级视频网站 | 成年人免费在线观看视频网站 | 日本精品视频在线播放 | 天堂av一区二区 | 国产欧美一区二区精品性色超碰 | 日韩视频第一页 | 99国产精品99久久久久久 | 久草成人在线 | √天堂8资源中文在线 | 一级久久久 | 免费av免费看 | 亚洲一区久久久 | 成年人午夜视频 | 五月天久久久久 | 国产无遮挡又黄又爽 | 骚虎在线视频 |