Seals 'brought TB to the Americas before Europeans'

The long-held idea that Europeans were the first to bring tuberculosis to the Americas when they arrived in the 15th Century has been thrown into doubt, the BBC reports.

Instead, a study suggests that the deadly disease was present in the area hundreds of years before Christopher Columbus made landfall.

Genetic tests reveal that humans were probably not responsible for moving TB to the New World at all - instead, seals carried it there.

The research is published in Nature.

Johannes Krause, from the University of Tuebingen, in Germany, said: "Who would have thought seals were actually transmitting one of the deadliest diseases to South America about a thousand years ago?

"That was definitely a big surprise."

When the Europeans arrived in the New World, they brought with them a deadly wave of diseases. It is estimated that 90% of Native Americans were wiped out by new infections.

But this study suggests at least one of these bugs - tuberculosis - was already circulating there.

Scientists have unearthed three ancient Peruvian skeletons that contain DNA from strains of TB. These 1,000-year-old remains predate the Europeans' arrival by about 500 years.

"We compared the genome - the entire genetic information - of these ancient strains with the modern bacterium that forms today'sMycobacterium tuberculosis complex and what we found was the ancient Peruvian strains were not typical European, Asian or African strains that we find in humans today," Prof Krause told BBC Radio 4's Inside Science program.

The puzzle was that while TB was spreading around Africa, Europe and Asia 1,000 years ago, scientists were unsure how a new and unusual strain jumped across the ocean to hit American people.

"We were thinking to ourselves: 'How did it get to Americas?' We were joking: 'Was it flying? Was it swimming?'" said Prof Krause.

"But then we saw it was indeed swimming. It was disseminated by seals."