When Napoleon ordered his army to retreat from Russia disaster followed in October 1812. About 300,000 soldiers died from hunger, cold, exhaustion and disease.
Now researchers say they have identified two unexpected diseases among soldiers who died during the retreat – paratyphoid and relapsing fever – providing new insight into their plight.
“I think the main thing is why [the retreat] there was such a failure, there was cold and hunger, etc. With or without infectious diseases, they would have died en masse anyway,” said Nicholas Rascovan, head of microbial paleogenomics at the Pasteur Institute and author of the study.
“But I think it's [does] Change is part of our knowledge of all infectious diseases.”
Article in the journal Current Biology.Raskovan and his colleagues describe how previous DNA tests of soldiers buried in the same mass grave in Vilnius, Lithuania, revealed evidence of typhus and trench fever.
However, this work was based on a very sensitive method called nested PCR, which involved screening samples for specific pathogens.
Using a different method called shotgun sequencing, Raskovan's team was able to find DNA fragments matching any of the 185 bacteria known to cause disease in humans.
The results, based on DNA from the teeth of 13 soldiers, which had not been previously studied, showed that one soldier was infected with a bacterium carried by lice. Recurrent Borrelias, which causes relapsing fever, and four others were infected with a variant of the bacterium Salmonella entericacausing paratyphoid fever, a disease transmitted through contaminated food or water. One of the four soldiers may also have had relapsing fever, the team said.
The researchers say the findings are consistent with historical descriptions of symptoms experienced by Napoleon's soldiers. Grand Armysuch as fever and diarrhea.
However, unlike previous studies, the team found no traces of the bacteria that cause typhus or trench fever.
Although Raskovan noted that these soldiers may not have been infected with these diseases or only had a mild infection, the results could alternatively be explained by the destruction of ancient DNA over time, or that the amount of DNA present was below the detection limit of the technique used.
The researchers ran a series of statistical tests and analyzes to ensure that their results were reliable and indicative of real infections.
These included looking for signs of DNA degradation that would be expected from genuine ancient DNA, and examining the DNA's place in the evolutionary “family tree” of the two bacteria.
“In light of our results, a reasonable scenario for the death of these soldiers would be a combination of fatigue, cold and several diseases, including paratyphoid and relapsing fever, which is transmitted by lice.
Relapsing fever, carried by lice, is not necessarily fatal, but can significantly weaken an already exhausted person,” they write.
Dr Michael Rowe, an expert in European history at King's College London, welcomed the research.
“Science is interesting because I think it does things that a historian couldn't do,” he said, referring to identifying diseases.
But he cautioned against the assumption that the army's devastation was simply due to harsh weather that left soldiers vulnerable to starvation and disease – a view promoted by Napoleon.
“It underestimates the role of the Russians and the fact that they are actually doing very smart things and that they [have] they have a very good strategy and they actually have a pretty sophisticated army,” he said.
