Salmonella infections could have been one of the contributing factors that resulted in a large number of deaths among the Aztecs that lived in Mexico before the Spaniards arrived. The die-off could have caused the fall of the Aztec empire.

Dramatic Decline Of The Aztec Population

The native population of the Aztecs is believed to number about 25 million when the Spanish explorers arrived in 1519. One hundred years later, however, the number of natives in the New World decreased to just 1 million.

Earlier studies suggested that the drop in the local population occurred mostly because of diseases that were brought by the European explorers, but until now no disease has been conclusively identified as responsible for the decline of the Aztec population.

Salmonella Enterica

In two new studies, researchers have suggested that a strain of salmonella could be behind the dramatic population drop.

Foodborne illnesses are often attributed to salmonella. Fears over salmonella contamination that could potentially cause illness often prompt recalls of food products but only a few of the salmonella serotypes are responsible for most foodborne illnesses.

The salmonella strain known as Salmonella enterica Paratyphi C is known to cause enteric fever, a bacterial infection with symptoms similar to those of typhoid fever and kills between 10 to 15 percent of those infected.

Researchers now think that this strain of salmonella could be what caused the illness that killed millions of natives in Mexico.

The Cocoliztli Epidemic That Killed 80 Percent Of Aztec Population

Study researcher Ashild Vagene, from the Max Planck Institute for the Science of Human History, and colleagues sequenced the DNA taken from the teeth of Aztecs that died during the cocoliztli epidemic that ran between 1545 and 1576.

The epidemic killed about 80 percent of the population. Several diseases including smallpox, measles, and typhus have been blamed for the outbreak but no solid evidence has yet been established to confirm any of the hypotheses. Using the metagenomic tool MALT to find traces of ancient pathogen, the researchers reported finding S. enterica in several of the samples they collected and analyzed.

"We propose that S. Paratyphi C contributed to the population decline during the 1545 cocoliztli outbreak in Mexico," the researchers reported in their study.

Salmonella Strain May Have Come From Europe

Researchers of the second study studied the remains of a woman who died in Norway 300 years before the cocoliztli epidemic occurred and found evidence of S. enterica. The discovery suggests that the salmonella strain present in the New World victims may have originated from Europe, albeit it was not clear how closely the strains matched.

"We recovered a draft Paratyphi C genome from the 800-year-old skeleton of a young woman in Trondheim, Norway, who likely died of enteric fever," study researcher Zhemin Zhou, from University of Warwick, and colleagues wrote.

Both studies, which have not yet been peer-reviewed, did not provide conclusive evidence that salmonella was the disease that caused the death of the Aztecs, however. The evidence though hints that it likely made a contribution to the eventual collapse of the Aztec empire.

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