Collapse of Aztec society linked to catastrophic salmonella outbreak (Noticias)

Dos estudios recientes, basados en DNA bacteriano de cerca de 500 años de antigüedad, extraído de los dientes de restos humanos exhumados en el centro del Estado de Oaxaca, sugieren que una de las peores epidemias en la historia de la humanidad —una peste del siglo XVI, llamada por los Aztecas “cocoliztli” (en Náhuatl), que devastó a cerca del 80% de la población nativa de México— pudo haber sido causada por Salmonella enterica subsp. enterica serovar Paratyphi C, traída de Europa por los conquistadores. Se estima que de 7 a 18 millones de personas murieron durante la epidemia entre los años 1545 y 1576.

Summary: Indigenous populations of the Americas experienced high mortality rates during the early contact period as a result of infectious diseases, many of which were introduced by Europeans. Most of the pathogenic agents that caused these outbreaks remain unknown. Using a metagenomic tool called MALT to search for traces of ancient pathogen DNA, it was possible to identify Salmonella enterica in individuals buried in an early contact era epidemic cemetery at Teposcolula-Yucundaa, Oaxaca in southern Mexico. This cemetery is linked to the 1545-1550 CE epidemic locally known as ‘cocoliztli’, the cause of which has been debated for over a century. Here we present two reconstructed ancient genomes for Salmonella enterica subsp. enterica serovar Paratyphi C, a bacterial cause of enteric fever. We propose that S. Paratyphi C contributed to the population decline during the 1545 cocoliztli outbreak in Mexico.

News article
By Ewen Callaway

One of the worst epidemics in human history, a sixteenth-century pestilence that devastated Mexico’s native population, may have been caused by salmonella from Europe, a pair of studies suggest. In one study, researchers say they have recovered DNA of the gut bacterium from burials in Mexico linked to an epidemic that killed up to 80% of the country’s native inhabitants in the 1540s.

Spanish conquistadors arrived in Mexico in 1519, when the native population was an estimated 25 million. A century later, after a series of epidemics, numbers had plunged to around 1 million. The largest of these outbreaks were known as cocoliztli, but there has been little consensus on their cause.

In an attempt to settle the question, a team led by evolutionary geneticist Johannes Krause at the Max Planck Institute for the Science of Human History in Jena, Germany, extracted and sequenced DNA from the teeth of 29 people buried in southern Mexico. All but five were linked to a cocoliztli that researchers think ran from 1545 to 1550. Bacterial DNA recovered from several of the people matched that of a Salmonella enterica strain called Paratyphi C.

This is potentially the first genetic evidence of the pathogen that caused the massive decline in native populations after European colonization, says Hannes Schroeder, an ancient-DNA researcher at the Natural History Museum of Denmark in Copenhagen. Yet María Ávila- Arcos, an evolutionary geneticist at the National Autonomous University of Mexico in Mexico City, isn’t convinced. She notes that if a virus caused the cocoliztli, it wouldn’t have been picked up by the team’s method.

Another study also raises the possibility that Salmonella enterica subsp. enterica serovar Paratyphi C arrived in Mexico from Europe. A UK-led team collected and sequenced the now-rare strain from the remains of a woman buried around 1200 in Norway. It is the earliest evidence of the strain, and shows that it was circulating in Europe 300 years before it appeared in Mexico.

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Journal reference: Åshild J. Vågene, Michael G. Campana, Nelly M. Robles García, Christina Warinner, Maria A. Spyrou, Aida Andrades Valtueña, Daniel Huson, Noreen Tuross, Alexander Herbig, Kirsten I. Bos, Johannes Krause. Salmonella enterica genomes recovered from victims of a major 16th century epidemic in Mexico. doi: https://doi.org/10.1101/106740.

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