A new study in Science suggests that changes in a gene in Yersinia Pestis; The bacteria that causes the plague, could have added to the length of two plague pandemics, including the pandemic that started with “black death”.
“Ours is one of the first research studies to examine directly the changes in an ancient pathogen, that which we still see today, in an attempt to understand what motivates the virulence, the persistence and the possible extinction of the pandemics,” said Hendrik Poinar, study author and director of the McMaster Ancient Dna Center, according to a press release.
The study suggests that less virulent plague bacteria could have caused longer plague pandemies – thanks to the fact that infected rodents lived (and distribute the plague) for longer periods before dying of their infections.
Find out more: Scientists reveal the original story of black death
The three plague pandemics
The bacteria Y. Pestis Infected rodents and humans and caused three main plague pandemics in humans, which have all continued for centuries after their initial epidemics. The first started in the 500s; The second started in the 1300s; And the third began in the 1800s (and still continued in certain regions of Asia, Africa and the Americas today).
Although the three pandemics are devastating at their start, the second pandemic was by far the most serious. Black death, its initial explosion, killed around 30 to 50% of the European population between 1347 and 1352 and – to date – represents the most deadly wave of disease in recorded history.
To find out more about how these plague pandemics have changed over time, scientists at McMaster University in Canada and the Institute’s Pastor in France turned to a Y. Pestis Virulence gene known as PLA. This gene is repeated several times throughout the Y. Pestis genome, and it allows the bacteria to spread without being detected throughout the body of infected individuals.
Find out more: These 4 pandemics have changed the course of human history
A gene and the plague
To study this gene, scientists have studied the historical strains of Y. Pestis Human remains and found that the number of APL repetitions decreased during the first and second pandemics of plague. Then scientists tested Y. Pestis The bacteria of the third pandemic, infecting mice with three strains that had reduced PLA rehearsals.
“These three samples allowed us to analyze the biological impact of these plans gene suppressions,” said Javier Pizarro-Cerdá, another author of the study and director of the Yersinia Research unit at the Pasteur Institute, according to the press release.
The results revealed that the exhaustion of APL decreases virulence and increases the length of the plague infections in mice. According to the authors of the study, these changes could have made rodents alive later in the last stages of the first and second pandemics, which allows them to spread their infections for a longer period.
“It is important to remember that the plague was an epidemic of rats, which were the engines of epidemics and pandemics. Humans were accidental victims. ” Poinar added to another press release.
Find out more: Bubonic plague and these other 4 diseases still exist today today
The continuous threat of Y. Pestis
Although PLA depletion occurred about 100 years after the start of the first and second pandemics, scientists emphasize that the two changes were random and unrelated.
“Our research highlights an interesting scheme of the evolutionary history of the plague. However, it is important to note that the majority of the strains which continue to circulate today in Africa, in the Americas and Asia are very virulent strains,” said Ravneet Sidhu, another study author and a doctorate. Student at McMaster Ancient DNA Center.
Although always a threat to current populations, Y. Pestis Infections are now much more manageable due to modern diagnoses and treatments.
“Today, plague is a rare disease, but which remains a public health problem and serves as a model to acquire a broad understanding of how pandemics emerge and go out. This example illustrates the balance of the virulence that a pathogen can adopt to propagate effectively, “Pizarro-Cerdá said in the press release.
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Sam Walters is a journalist covering archeology, paleontology, ecology and the evolution of Discover, as well as an assortment of other subjects. Before joining the Discover team as a deputy editor in 2022, Sam studied journalism at the Northwestern University in Evanston, Illinois.
