Tags: TB | sea lions | seals | research

Sea Lions, Seals Brought Tuberculosis to the New World

By Jennifer G. Hickey   |   Thursday, 21 Aug 2014 10:57 AM

New research shows that tuberculosis was likely transported across the oceans from Africa to South America by seals and sea lions long before Europeans reached the continent, reports the journal Nature.

The full paper, "Pre-Columbian Mycobacterial Genomes Reveal Seals as a Source of New World Human Tuberculosis," was first published in Nature.

It was originally thought that TB, which emerged 70,000 years ago, was acquired by humans before they departed Africa and introduced by the Spaniards when they colonized South America. But the researchers found evidence that placed that common opinion into doubt.

Even one genetic study published in 2013 estimated that all human tuberculosis strains evolved from a common ancestor that lived 70,000 years ago, National Geographic reported.

An analysis conducted by the scientists of tuberculosis DNA recovered from three 1,000- to 1,300-year-old Peruvian skeletons revealed that the strain in the bones did not match the strain brought to the New World by European explorers.

Modern TB strains found in North and South America are about 1,000 years old and are similar to from Europe, which has long led scientists to believe the Spaniards were responsible for spreading the disease in the sixteenth century.

"This is a landmark paper that challenges our previous ideas about the origins of tuberculosis, not just in the Americas but in the Old World too," Terry Brown, a biomolecular archaeologist at the University of Manchester, England, told Nature.

In 2012, about 8.6 million people worldwide were stricken ill by TB, according to the World Health Organization.

A total of 1.3 million people died from TB in 2012 and it remains on the world's most top infectious killers. Almost 95 percent of deaths occurred in low- and middle-income countries.

"We found that the tuberculosis strains were most closely related to strains in pinnipeds, which are seals and sea lions," researcher Anne Stone, Arizona State University School of Human Evolution and Social Change professor told ASU News.

Research teams from the Wellcome Trust Sanger Institute in the United Kingdom and the Swiss Institute for Tropical and Public Health were collaborators on the study.

The importance of the new findings helps to explain how "a mammalian-adapted pathogen that evolved in Africa around 6,000 years ago could have reached Peru 5,000 years later," added Stone's co-investigators, Johannes Krause of Germany's University of Tubingen.

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