Study: Seals may have first carried tuberculosis to the New World

New research suggests that seals may have first brought tuberculosis to the Americas hundreds of years before Christopher Columbus and his crew stepped ashore.

Bacterial genome sequencing of three ancient Peruvian skeletons of people found to have died from the disease about 1,000 years ago found their genotypes structurally different from European TB strains.

While modern strains found in the Americas are closely related to strains from Europe, suggesting that Spanish colonists first carried the disease to the New World, the ancient strains of TB found in the Peruvian bones were most similar to a strain of TB carried by seals and sea lions, according to research published Wednesday in the science journal Nature.

The researchers theorize that seal-hunting humans on the coast contracted the strain about 2,000 years ago by eating the animals.

“There were signs that the disease existed previous to the discovery of the New World. But it is the first time now that the pathogen of pre-Columbian tuberculosis could be identified,” said researcher Sebastien Gagneux of the Swiss Tropical and Public Health Institute.

Tuberculosis is a highly infectious, deadly disease that helped kill 90 percent of the Native American population after European colonists reached the New World.

With tuberculosis becoming resistant to the three antibiotics currently used to fight the disease, the discovery can shed light on what Krause called the mutation rate of the pathogen, whose drug-resistant mutations kill more than 50 percent of those infected, most of them in developing countries.

“This is very important information to learn more about the evolutionary rates of pathogens over longer time periods,” lead researcher Johannes Krause of the University of Tuebingen in Germany told Nature.

Krause added, however, that because this ancient strain of tuberculosis does not exist in people today, the researchers cannot conclude that it could be transmitted from human to human. “To nail this hypothesis, we would have to find tuberculosis in North America and in inland populations in South America,” he said.

Tuberculosis is an airborne disease that can take years to develop before a patient shows active symptoms. Roughly one-third of the world’s population is estimated to be infected with TB, and about 1.3 million people became sick last year, according to statistics from the World Health Organization (WHO). More than 20 percent of all cases are attributable to smoking.

TB is believed to have killed more people than all wars and famines combined, according to the WHO.