Researchers extracted and sequenced DNA from the teeth of thirteen soldiers from a mass grave in Vilnius, Lithuania, on the route of retreat from France to Russia. After removing environmental contaminants, DNA fragments from pathogenic bacteria were identified: not typhus, butSalmonella enterica – Enteric fever/paratyphoid fever and Borrelia recurrentis , which causes relapsing fever that is also transmitted by body lice
In the summer of 1812, French Emperor Napoleon Bonaparte led an invasion force of about half a million soldiers into the Russian Empire. By December, only a few were left alive. Historical records have attributed the collapse to hunger, cold, and typhus. A new study published October 24 in theCurrent Biology From Cell Press, microbial paleogenomics researchers extracted DNA from the soldiers' teeth—and found no trace of typhus. Instead, they identified two pathogens known as enteric fever and relapsing fever, diseases that allegedly contributed to the defeat.
“It is exciting to use the technology available today to locate and diagnose something that has been buried for two centuries,” says lead researcher Dr. Nicolas Rascouban of the Institut Pasteur, Paris.
For generations, historians have debated the causes of the disaster. Doctors and officers of the time tended to blame typhus, a disease common in the armies of the time. The discovery of body louse parasites on the bodies of soldiers, the main vector of typhus, and even DNA fromRickettsia prowazekii , the bacteria that causes typhoid, strengthened the hypothesis.
Now, using ancient DNA technologies, the team sought to reexamine whether typhus was indeed at play. The researchers extracted and sequenced DNA from the teeth of thirteen soldiers from a mass grave in Vilnius, Lithuania, on the route of retreat from France to Russia. After environmental contaminants were removed, DNA fragments from pathogenic bacteria were identified: not typhus, butSalmonella enterica – Enteric fever/paratyphoid fever andBorrelia recurrentis , which causes relapsing fever that is also transmitted with body lice.
However, the researchers did not findR. prowazekii אוBartonella quintana (trench fever), which were identified in previous studies in other soldiers from this site. Raskoven explains that the discrepancy may be due to differences in technology: Early work relied on PCR, which replicates specific DNA segments, but ancient DNA breaks down into pieces that are too short for this method. “Our approach casts a wider net and captures a wide range of DNA sources based on the very short sequences,” he says.
To their surprise, the researchers associated the strain ofB. recurrentis found in Napoleon’s soldiers to the same lineage that was recently discovered in ancient Britain some 2,000 years ago during the Iron Age. This lineage appears to have survived in Europe for thousands of years, while all modern strains sequenced so far belong to a different lineage. “This shows the power of ancient DNA to reveal a history of infectious diseases that cannot be reconstructed from contemporary samples,” Raskoven concludes.
Funding: European Research Council (ERC) Pasteur Institute, French National Center for Scientific Research (CNRS), and French National Research Agency (ANR).
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