Wild Hypothesis Links The Bubonic Plague to Modern Oral Health : ScienceAlert

The deadliest epidemic on record may continue to plague human oral health centuries later and may contribute to some modern cases of gum disease.

This remains largely a hypothesis, but if this correlation holds up to future studies, it could shed light on unintended long-term consequences of infectious respiratory diseases.

The microbiota that live in the human mouth, nose, and pharynx are the second largest community of microorganisms in our body after the gut. Now, one of the first studies to trace its historical evolution has identified a key shift that coincided with the Black Death in the late Middle Ages.

The study, led by Penn State scientists, was based on genetic analysis of ancient tooth samples from 235 people who lived in Britain between 2200 BC and 1853 AD.

More than half of them lived in London, where waves of plague claimed tens of thousands of lives over the centuries.

An international team of scientists said that since its birth in the 14th century, the city alone has lost 30% to 50% of its population in just three years, “dramatically changing the city's demographic structure and lifestyle.”

Across all the ancient British teeth analyzed, the team found 954 microbial species, broadly divided into two distinct communities.

After the second plague pandemic reached London in 1348, the composition of these communities appears to have changed.

Microbial communities dominated by genus Methanobrevibacter After appearing about 2,200 years ago but disappearing around 1853, it is now largely extinct among modern industrialized populations

Meanwhile, more modern microbial communities show lower bacterial diversity and are dominated by genera Streptococcus – Communities that tend to support bacteria associated with periodontal disease.

This suggests that the modern origins of gum disease “may actually stem from Streptococcus-related communities,” the author writes.

The Black Death was not responsible for all of these changes, but according to statistical analysis, time-related factors including its arrival could explain nearly 11% of the historical changes in London's oral microbiome.

While this finding requires further examination, temporal changes in oral microbiome composition that coincided with London's second plague pandemic may be the result of disease selection and susceptibility during the pandemic,” the researchers wrote. They also showed , advances in public health, diet, and culture following the plague may have led to changes in the human oral microbiome.

“We know that survivors of the second pandemic had higher incomes and were able to afford higher-calorie foods,” explains Laura Weyrich, an anthropologist at Penn State University. .

“The epidemic may have triggered changes in people's diets, which in turn affected the composition of their oral microbiomes.”

For example, after the Black Death, people in London ate more expensive foods such as fish, meat, and wheat bread.

The pandemic may also have changed the genetics of urban populations in ways that indirectly affect the oral microbiome.

Recent DNA analysis of Black Death victims suggests that the deadly epidemic triggered genetic changes in humans that persist to this day.

For example, people with an ERAP2 gene mutation in the 14th century had approximately a 40% to 50% increased survival rate if infected with the bacterium that caused the plague. Yersinia pestis.

Now, it has been discovered that the same copy of the ERAP2 gene may reduce the risk of respiratory infections such as COVID-19 while increasing the risk of autoimmune diseases such as Crohn's disease, type 1 diabetes, and rheumatoid arthritis.

Therefore, changes in the genetic makeup of the post-plague population may have increased the risk of diabetes. An increased risk of diabetes, then, may in turn increase the risk of gum disease.

The team doesn't yet know why Methanobrevibacter– the relevant community disappears in the UK, or if StreptococcusIn fact, dominating the community is the leading cause of periodontitis. But Weyrich and her colleagues did find that, at least in London, periodontal disease was significantly associated with the composition of the oral microbiome.

In London, Weyrich and her colleagues found that periodontal disease was significantly associated with the composition of the oral microbiome.

The authors behind the study were unable to prove cause-and-effect for their results, but the apparent indirect link between respiratory disease, immune problems and oral health is enough to suggest further research should be conducted.

“Uncovering the origins of these microbial communities may help understand and manage these diseases,” Weirich said.

The study was published in natural microbiology.

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