Pest already over 20 million years old?

Fossil flea bacteria could be ancestors of the Black Death

Contained in amber for 20 million years, this flea may contain ancient ancestors of the plague-causing agent Yersinia pestis. © George Poinar, Jr. / Oregon State University
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Ancient Plague: In a primeval amber-preserved flea, a US researcher has discovered possible pest growth. The bacteria from the 20-million-year-old fossil are very similar to today's pathogens of the disease. This may indicate that the plague is much older than thought - and older than humans. The plague might even have affected the dinosaurs, the scientist speculates.

In the late Middle Ages, the plague sought out all of Europe as a "black death": more than half of the European population fell victim to the disease in the 14th century. In the sixth century, a similarly severe epidemic, the Justinian plague, depopulated the mid-range across the Middle East and possibly as far as China.

Plague in humans for 20, 000 years

The origins of these epidemics are now known: Climatic changes in Asia probably drove the disease-transmitting fleas in search of new hosts. The pestering bacteria of the species Yersinia pestis were thus transferred from rats to other animals, and finally to humans.

From the last two millennia to today there are numerous documented plague epidemics. All today still occurring strains of the plague bacteria are descendants of the "black death". According to popular theories, the deadly interplay between rats, humans, and between them the fleas as transmitters already arose 10, 000 to 20, 000 years ago. Even the early modern humans would have had to fight with the plague.

Old bacteria resemble today's Pesterregern

But a fossil find in a drop of amber now suggests that the pathogens could be much older - far older than humans. In an approximately 20-million-year-old drop of amber from the Dominican Republic, a trapped flea has stood the test of time. Finds of fleas in amber are very rare, but in this flea, George Poinar, an expert in amber fossils from Oregon State University, found something truly unique: remnants of bacteria that closely resemble today's metastases. display

On the trunk of the flea is a dried-up drop full of bacteria (arrow). George Poinar, Jr. / Oregon State University

The size and shape of the fossil bacteria is almost identical to those of today's Yersinia pestis: they appear both globular and stature-like. The Pesterreger are the only occurring today, pathogenic bacteria with this appearance.

Bacterial plug in the suckling bowl

But the similarities go far beyond the appearance: The researcher found a greater concentration of bacteria in the rectum of the enclosed flea. There, the pathogens accumulate even in modern life.

The mouthpiece of the insect also contained a drop of dried liquid containing the potential plague ancestors. This fits in with the current transmission mechanism of the pathogens: After sucking blood, a large mass of bacteria often clogs the flea's root. To be able to drink again, the bloodsucker first has to get rid of this graft. He presses the bacteria into the blood vessels of the next host animal.

Plague already with the dinosaurs?

According to the insect researcher Poinar, the pest irritants could have developed as a host organism even without humans. As parasites in early rodents, they could have spread with the same mechanism as they do today. It was only about 20, 000 years before the bacterial strains developed, which can also affect humans. "If this is an ancient strain of Yersinia, that would be outstanding, " says Poinar. "That would show that the plague is truly an age-old disease that undoubtedly infested and eventually eradicated animals long before humans existed."

The plague could therefore have played a bigger role in world history than previously thought, even far beyond the medieval changes in the wake of the Black Death: flea-like insects already existed far earlier, back to the time of the dinosaurs. The diseases transmitted by them could even have contributed to the extinction of giant lizards, Poinar speculates. (Journal of Medical Entomology, 2015; doi: 10.1093 / jme / tjv134)

(Oregon State University, 29.09.2015 - AKR)