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| Research found that ancient people were infected with the earliest plague 5,000 years ago, lacking key genes for fleas transmission |
Plague is a severe infectious disease mainly transmitted by Yersinia pestis through rodent fleas.
Historically, it was a pandemic that caused high mortality
.
It was called the "Black Death" in the 14th century and killed as much as half of Europe's population
On June 29, a genetic analysis published online by Cell Reports, a journal of Cell Press, revealed that the ancient strain found may not be as infectious and deadly as the medieval strain
.
The research team came from the University of Kiel in Germany, the University of Gothenburg in Sweden, the University of Latvia, and the University of Tartu
"The most surprising thing is that the emergence of Yersinia pestis was 2000 years earlier than the previously published research results
.
" said Ben Krause-Kyora, the corresponding author of the paper and director of the aDNA laboratory at the University of Kiel in Germany.
Studies have shown that the hunter-gatherer carrying Yersinia pestis is a 20-30 year old man named "RV 2039"
.
At the end of the 19th century, people excavated the remains of two ancients in the Rinnukalns region of present-day Latvia, and he is one of them
The Krause-Kyora team used the teeth and bone samples of all four remains, sequenced their genomes, and then tested the bacterial and viral pathogens they carried
.
They were surprised to find that Yersinia pestis was present in RV 2039
After reconstructing the bacterium's genome and comparing it with other ancient strains, the researchers determined that the Yersinia pestis carried by RV 2039 was indeed the oldest such strain found to date
.
It may be part of a bacterial lineage that appeared about 7000 years ago, only a few hundred years after the Yersinia pestis was isolated from its predecessor, Yersinia pseudotuberculosis
"It is surprising that we have seen a more or less complete gene set of Yersinia pestis in this early strain, and only a few genes are lacking
.
But even a small change in the gene can cause toxicity to the bacteria.
In particular, this ancient strain lacks a key gene: the gene that originally allowed fleas to act as a transmission medium
.
This gene is responsible for effectively spreading the bacteria to the human host, causing pustule-filled lymph nodes to grow with the black death patients in the Middle Ages
.
The flea-mediated transmission also requires the death of the human host, which means that the emergence of this gene may cause related diseases to be more deadly
.
It is worth noting that starting from RV 2039, Yersinia pestis may have taken more than 1,000 years to acquire all the mutations needed for flea transmission
.
According to the study, it is unclear to what extent the health of RV 2039 has been affected by the plague
.
The researchers said that Yersinia pestis was found in the blood of RV 2039, which means that he is likely to die from a bacterial infection, although the development of this disease in him may be quite slow
.
The researchers observed that when RV 2039 died, there were a lot of bacteria in his blood, and in previous rodent studies, the high bacterial load of Yersinia pestis was associated with a less aggressive infection
.
In addition, the people buried near RV 2039 were not infected, and RV 2039 was also carefully buried in the grave.
Therefore, researchers believe that he is unlikely to be infected with a highly infectious respiratory plague
.
Instead, the researchers speculated that the 5,000-year-old strain was probably transmitted directly through the bite of an infected rodent, and it may not have spread outside the infected person
.
"Isolated cases of infection from animals to humans can also explain why these ancient patients lived in different social environments
.
We can see the plague in societies such as grassland herders, hunter-gatherer fishermen and farmers
.
These social environments It's completely different, but there are always cases of plague that happen spontaneously
.
" Krause-Kyora said
.
Researchers believe that studying the history of Yersinia pestis may help reveal the history of the human genome
.
"Different pathogens and the human genome always evolve together
.
We know that the plague is likely to kill half of Europeans in a short time, so it should have a significant impact on the human genome
.
" Krause-Kyora said, "but even before that , The human immune gene has undergone major changes at the end of the Neolithic Age, which may reflect the major changes in the pathogen pattern at that time
.
"
Link to the paper: https://
