New Delhi, October 25 (IANS). When Napoleon ordered his army to retreat from Russia in October 1812, disaster struck. Nearly 3 lakh soldiers died battling hunger, cold, exhaustion and diseases. Decades later, some researchers have revealed the real secret on the basis of DNA analysis. This study shows that lice were also a cause.
DNA analysis of the teeth of soldiers buried together showed that the soldiers had paratyphoid fever and relapsing fever. Researchers say they have identified two unknown diseases – paratyphoid fever and relapsing fever – in the soldiers who died during the retreat, which provides new information about their condition.
This research was published in Current Biology Journal. In which Nicholas Raskovan, head of the Microbial Palaeogenomics Unit at the Institut Pasteur and author of this study, and his colleagues explained how previous analysis of the DNA of soldiers buried in the same mass grave in Vilnius, Lithuania had found evidence of typhus and trench fever.
However, that work was based on a very sensitive technique called nested PCR, which involved screening samples for specific pathogens.
Using a different technique called shotgun sequencing, Raskovan’s team was able to find DNA fragments that matched any of the 185 bacteria that cause disease in humans.
The results, based on DNA taken from the teeth of 13 soldiers who had not previously been studied, showed that one soldier was infected with the louse-borne bacteria Borrelia recurrentis, which causes relapsing fever, and four other soldiers were infected with a type of bacteria called Salmonella enterica, which causes paratyphoid fever. This disease spreads through contaminated food or water. The team said that one of these four soldiers could also have relapsing fever.
The researchers say the results match descriptions of symptoms, such as fever and diarrhea, experienced by soldiers of Napoleon’s Grand Army.
However, unlike previous studies, the team found no signs of the bacteria that cause typhus or trench fever. Raskovan believes that these soldiers may not have been infected with these diseases, or may have had only a mild infection, but these results could also be explained in other ways, such as the degradation of buried DNA over decades, or the amount of DNA available was below the detection limit of the technique used.
The researchers conducted a number of statistical tests and analyzes to ensure that their results were accurate and indicative of a true infection.
This involved looking at the traces of DNA degradation that would be expected from real old DNA, and figuring out where the DNA falls in the evolutionary “family tree” of both bacteria.
They write, “Given our results, the true cause of death of these soldiers may be a combination of fatigue, cold, and several diseases, including paratyphoid fever and relapsing fever caused by louse. Although relapsing fever caused by louse is not necessarily fatal, it can greatly debilitate an already exhausted person.”
–IANS
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