A study published in the scientific journal Current Biology reveals new diagnoses of deceased French soldiers who were a part of Emperor Napoleon Bonaparte I’s invasion of Russia in 1812. New techniques and advancements in DNA sequencing were used to determine the presence of two disease agents previously unknown to have afflicted the fleeing soldiers: Salmonella enterica, which causes paratyphoid fever and Borrelia recurrentis, causes a relapsing fever. These new findings reveal the role these and possibly other diseases had in the downfall of Napoleon’s army as they fled from Russia during the onset of winter.
Napoleon Bonaparte, one of the most famous and recognizable military generals in history, had nearly all of Europe under his power and control by 1812. Additionally, he was married to the daughter of the emperor of the at-the-time superpower, Austria: Marie Louise. During this time, he largely succeeded in forbidding the continent from trading with Great Britain in hopes of weakening the island nation and allowing him to conquer it as well. Nonetheless, the Russian Empire resisted these demands to cease trade, which prompted Napoleon to launch a massive invasion consisting of 600,000 men into Russia to end the defiance and further starve Britain. However, as Napoleon’s army reached Moscow, it was completely evacuated, and the crops were burned, with no supplies left that could maintain the army. Eventually, the approach of the harsh Russian winter forced Napoleon to retreat only six months later — ending the invasion in infamy as an estimated only tens of thousands men returned alive to France and eventually contributed to his fall from power only a few years later.
Historians have long debated what factors led to the collapse of the retreating Napoleonic army from hunger to illness to the extreme cold of the Russian winter, which has contributed to multiple studies focusing on the issue. In 2006, researchers studied samples of DNA from soldier remains of the army that had been found buried in a massive grave site accidentally uncovered in 2001 in Vilnius, Lithuania during a construction project in one of the northern suburbs of the city — containing two to three thousand men buried soon after they died. This study, which used the polymerase chain reaction (PCR) technique to create millions of copies of short DNA segments in order to detect the DNA sequences of specific pathogens in dental samples of the soldiers, found traces of two disease agents: Rickettsia prowazekii (responsible for typhus) and Bartonella quintana (responsible for trench fever).
While the PCR technique used in this study was useful in verifying the presence of microorganisms thought to be present in the remains of the soldiers, it remains largely blind when used for identifying unsuspected diseases. This limitation along with the rise of exponentially more sophisticated DNA sequencing technology present today, prompted this most recent study authored by former postdoctoral fellow at the Institut Pasteur in Paris, Rémi Barbieri, and palaeogenomicist at Pasteur Institute in Paris, Nicolás Rascovan. Using the new technique, high-throughput sequencing, millions of degregated and chemically altered DNA fragments were studied from the teeth of thirteen soldiers through decontamination, grinding into a bone powder, and dissolving it.
The process identified a wide array of pathogens, four of the thirteen soldiers were shown to have Salmonella enterica (responsible for paratyphoid fever characterized by a loss of appetite and rose-colored spots), and two of the thirteen soldiers were shown to have Borrelia recurrentis (carried by lice and responsible for relapsing fever characterized by recurring episodes of high fevers). Interestingly enough, the originally identified Rickettsia prowazekii and Bartonella quintana in the 2006 study were not found again in these recent tests — leading to speculation that those agents either not spread to the small sample group or had snuck beneath the new sequencing technique due to it being less sensitive than the old PCR method in some manner.
Rascovan has stated that he believes a break from the investigation would be instrumental in furthering the progress of the study, as most of the dental samples have already been analyzed at the Lithuania site and preserving remaining samples to be used when “we have more powerful techniques to do things we cannot even imagine today.”
