Scientists have long debated whether human body lice could have helped drive the rapid spread of the bacteria responsible for the deadly plague in the Middle Ages. known as the Black Death.
It’s clear that rat fleas played an important role, but some population studies have suggested that bites from these fleas may not have been enough to trigger a plague that killed tens of millions of people in Europe, Asia and other countries in the 14th century.
A study published Tuesday in PLOS Biology suggests that body lice may be more efficient at transmitting the plague bacteria, Yersinia pestis, than previously thought and therefore may have helped drive bubonic plague pandemic numbers.
Body lice they are parasites that can spread disease and often affect people living in overcrowded conditions. They are different from lice, which are much more common in the US and usually affect school-age children. Both insects feed on human blood.
“There is a long-standing medical historical debate about the Black Death pandemic in Europe,” said senior author Joe Hinnebusch, who was a senior investigator at the Bacteriology Laboratory at the National Institute of Allergy and Infectious Diseases in Hamilton, Montana, when the research has been started. being carried out. He is now retired.
Studies looking at how quickly the plague spread in the Middle Ages have suggested that another blood-sucking insect may have played a role, Hinnebusch said.
The researchers first examined the possibility that human fleas — there are thousands of species of fleas and some specifically bite humans — could have helped spread the disease. It turned out that human fleas were not good at spreading the bacteria.
Next, Hinnebusch and his team turned their attention to lice. The researchers carried out a series of laboratory experiments in which lice were allowed to feed – through a specially constructed artificial skin – on blood samples infected with Yersinia pestis at levels similar to those found in real cases of human plague. Sure enough, the lice picked up the bacteria.
Once infected, the lice were placed on another piece of artificial skin and sucked out with sterile blood. Later, when researchers tested the remaining, previously sterile blood sample, they discovered that it had indeed become infected through interaction with the lice.
“It is possible to observe transmission as early as the first day, but more bacteria were transmitted from the third to the seventh day after infection,” said Hinnebusch.
Although plague cases are mostly a thing of the past in the U.S., between one and 17 cases are reported each year, according to the Centers for Disease Control and Prevention. Majority occurred in the rural west. O Plague bacteria are believed to have been transported to the US around 1900 by rat-infested ships, according to the CDC.
The new study could help explain what happened in the Middle Ages, said Dr. Meghan Brett, an associate professor of infectious diseases at the University of New Mexico in Albuquerque.
“Around 30% to 50% of the population died during the pandemic,” she said. “One of the things that has been difficult to explain is how it was transmitted. It was suggested that rats and fleas were not enough. So this study is actually quite interesting and potentially came up with an explanation.”
Because the new study was conducted in a laboratory, it is not possible to know what proportion of real-life infections were transmitted by lice, said Dr. William Schaffner, professor of infectious diseases at Vanderbilt University Medical Center.
“We’ve known that rats and other rodents play an important role for a long time,” Schaffner said. “We now know that lice can also transmit the bacteria.”
In the U.S., people usually contract the plague from being bitten on the leg by a prairie dog flea when hunting or walking near the rodents’ burrows, Schaffner said.
Once infected, the person’s groin lymph nodes swell. Quick medical attention and antibiotic treatment can eliminate the infection.
But the scenario is not always so positive.
If a person is in a dusty environment and breathes in the bacteria, they could develop pneumonia, Schaffner said. “This is really bad,” he said. “Within a few days they can become deathly ill.”
This article was originally published in NBCNews. with
