Archeology Science X-Files

‘Black Death’: Salmonella May Have Wiped Out Aztecs 500 Years Ago, Scientists Say

‘Black Death’: Salmonella May Have Wiped Out Aztecs 500 Years Ago

Once-great Mayan cities still lie hidden under dense rainforest. To the average American, how this happened is a mystery. Some people say the Aztec nation “disappeared” and blame it even on alien invaders. However, the Maya aren’t gone at all. Millions of them still live in Guatemala and Honduras, and thousands more come to the United States to eke out livings as migrant laborers. It didn’t take a supernatural force to put their civilization into decline, either. All we know that in the 100 years following the Spanish conquest of Mexico, the native population fell from approximately 25 million to 1 million. The vast majority died in a single outbreak in the 1540s and now, new research may finally have identified why.

In 1545, disaster struck Mexico’s Aztec nation when people started coming down with high fevers and headaches, bleeding from the eyes, mouth and nose. Death generally followed in three or four days.

‘Black Death’: Salmonella May Have Wiped Out Aztecs 500 Years AgoBy extracting and sequencing the DNA from the teeth of 29 people buried at a grave site in Oaxaca, Mexico, a team of scientists from the Max Planck Institute for the Science of Human History were able to reconstruct the genome of the Salmonella enterica strain known as Paratyphi C. Photo©Reuters

Within five years, as many as 15 million people — an estimated 80 percent of the population — were wiped out in an epidemic the locals named “cocoliztli.”

The word means “pestilence” in the Aztec Nahuatl language. Its cause, however, has been in question for nearly 500 years.

On Monday, scientists swept aside smallpox, measles, mumps, and influenza as likely suspects, fingering a typhoid-like “enteric fever” for which they found DNA evidence on the teeth of long-dead victims.

“The 1545-50 cocoliztli was one of many epidemics to affect Mexico after the arrival of Europeans, but was specifically the second of three epidemics that were most devastating and led to the largest number of human losses,” said Ashild Vagene of the University of Tuebingen in Germany.

“The cause of this epidemic has been debated for over a century by historians and now we are able to provide direct evidence through the use of ancient DNA to contribute to a longstanding historical question,” she told the French Press Agency (AFP).

Vagene co-authored a study published in the science journal Nature Ecology & Evolution.

‘Black Death’: Salmonella May Have Wiped Out Aztecs 500 Years AgoSkull with mosaic inlay of turkois, shells and mother-of-pearl. Mixtecs/Aztecs, Mexico. Ca. 15th century. State museum of Ethnology, Leiden, The Netherlands

The cocoliztli outbreak is considered one of the deadliest epidemics in human history, approaching the “Black Death” bubonic plague that felled some 25 million people in western Europe in the 14th century – about half the regional population.

European colonisers spread disease as they ventured into the New World, bringing germs that local populations had never encountered, and therefore had no immunity against.

The 1545 cocoliztli pestilence in what is today Mexico and part of Guatemala came just two decades after a smallpox epidemic killed an estimated 5-8 million people in the immediate wake of the Spanish arrival.

‘Strong candidate’

A second cocoliztli outbreak from 1576 to 1578 killed half the remaining population.

“In the cities and large towns, big ditches were dug, and from morning to sunset the priests did nothing else but carry the dead bodies and throw them into the ditches,” is how Franciscan historian Fray Juan de Torquemada is cited as chronicling the period.

Even at the time, physicians said the symptoms did not match those of better-known diseases such as measles and malaria.

Finally scientists said they have likely unmasked the culprit.

Analysing DNA extracted from 29 skeletons buried in a cocoliztli cemetery, they found traces of the salmonella enterica bacterium, of the Paratyphi C variety.

‘Black Death’: Salmonella May Have Wiped Out Aztecs 500 Years AgoSalmonella bacteria, a common cause of foodborne disease, invade an immune cell. Credit: NIAID

It is known to cause enteric fever, of which typhoid is an example. The Mexican subtype rarely causes human infection today.

Many salmonella strains spread via infected food or water, and may have traveled to Mexico with domesticated animals brought by the Spanish, the research team said.

Salmonella enterica is known to have been present in Europe in the Middle Ages.

“We tested for all bacterial pathogens and DNA viruses for which genomic data is available,” and salmonella enterica was the only germ detected, co-author Alexander Herbig, also from Tuebingen University, told AFP.

It is possible, however, that some pathogens were either undetectable, or completely unknown.

“We cannot say with certainty that S. enterica was the cause of the cocoliztli epidemic,” said team member Kirsten Bos.

“We do believe that it should be considered a strong candidate.”

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‘Black Death’: Salmonella May Have Wiped Out Aztecs 500 Years Ago, Scientists Say
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