Latest discovery
Paratyphoid fever and relapsing fever in 1812 Napoleon's devastated army
• Genetic evidence of S. Paratyphi C and B. recurrentis in Napoleonic soldiers
• Phylogeny-driven authentication workflow for ultra-low-coverage pathogen aDNA
• Historical descriptions of the soldiers' illnesses match paratyphoid fever symptoms
• Multiple infections likely contributed to the collapse of Napoleon's 1812 campaign
During Napoleon's retreat from Russia in 1812, countless soldiers of the French army succumbed to infectious diseases, but the responsible pathogen or pathogens remain debated. We recovered and sequenced ancient DNA from the teeth of 13 soldiers who, based on historical records, likely died from infectious diseases, aiming to identify the pathogens responsible for their deaths. Our results confirmed the presence of Salmonella enterica subsp. enterica belonging to the lineage Paratyphi C, the causative agent of paratyphoid fever; and Borrelia recurrentis, responsible for relapsing fever transmitted by body lice. We were not able to detect Rickettsia prowazekii (the agent of typhus) and Bartonella quintana (the cause of trench fever), which had previously been associated with this deadly event, based on PCR results and historical symptom descriptions. The presence of these previously unsuspected pathogens in these soldiers reveal that they could have contributed to the devastation of Napoleon's Grande Armée during its disastrous retreat in 1812.
In June of 1812, Napoleon I, the French emperor, assembled a military force of about 500,000–600,000 soldiers to invade Russia. After arriving in Moscow without decisively defeating the Russian army, the Napoleonic forces, finding themselves isolated in a ruined city, opted to initiate a retreat and to establish winter encampments along the border with Poland in October that year. The retreat from Russia spanned from October 19 to December 14 1812 and resulted in the loss of nearly the entire Napoleonic army. According to historians, it was not the harassment from the Russian army that claimed the lives of about 300,000 men, but rather the harsh cold of the Russian winter, coupled with hunger and diseases. A doctor during the Russian campaign, J.R.L. de Kirckhoff, authored a book detailing the illnesses that afflicted soldiers in 1812. Specifically, he documented the prevalence of typhus, diarrhea, dysentery, fevers, pneumonia, and jaundice. Other physicians, as well as officers, made similar observations about the illnesses affecting soldiers. Different infectious diseases, such as typhus, have been described in French regiments even before the start of the Russian campaign. Typhus, in particular, which is commonly referred to as camp fever due to its frequent association with armies, has long been suspected of being the main infectious cause of the demise of the Grande Armée in 1812. This assumption was fueled by the discovery of body lice, the main vector of typhus, among the remains of Napoleonic soldiers who perished during the Great Retreat from Russia in December 1812 in Vilnius, Lithuania, as well as by the alleged identification of R. prowazekii and B. quintana sequences amplified by nested PCR in some of these individuals.3 However, this earlier study was limited by the technologies available at the time and relied solely on the amplification of two short DNA fragments (192 and 429 base pairs [bp] long), which did not offer sufficient resolution to provide unambiguous evidence for the presence of these pathogens in Napoleon's army. Several years later, another study successfully detected Anelloviridae viral ancient DNA (aDNA) in Napoleonic soldiers recovered in Kaliningrad in 1812, but these viruses are ubiquitous and asymptomatic in human populations and therefore unrelated to the fatal fate of these soldiers. Using state-of-the-art aDNA methodologies, we reanalyzed samples from Napoleonic soldiers who died in Vilnius and identified pathogen-specific genetic material, providing direct evidence of infectious agents that may have contributed to the army's collapse.
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