I live in a part of the US where it's not unusual to see headlines about cases of human plague every year. Rat fleas are still carriers of the once-dreaded disease, which is now treatable with antibiotics. In the 1300s it decimated whole populations in Europe and became known as the Black Death.
Let's go back in time even further, all the way back to 20 million years ago. A flea fell into sticky amber and was preserved for the ages in the amber mines now found in the Dominican Republic. It came into the hands of Oregon State University entomology researcher George Poinar, Jr. He found what could be the fossilized ancestor to the bubonic plague clinging to the flea.
"Aside from physical characteristics of the fossil bacteria that are similar to plague bacteria, their location in the rectum of the flea is known to occur in modern plague bacteria," Poinar said. "And in this fossil, the presence of similar bacteria in a dried droplet on the proboscis of the flea is consistent with the method of transmission of plague bacteria by modern fleas."
It may not be possible to say for sure if the bacteria really is a plague ancestor, but it matches the "size, shape and characteristics" of the modern plague bacteria. If it's true, this opens a new chapter in plague history.
"It would show that plague is actually an ancient disease that no doubt was infecting and possibly causing some extinction of animals long before any humans existed," Poinar said. "Plague may have played a larger role in the past than we imagined."
Entomology Today reported this week that four cases of human plague have been confirmed in New Mexico alone. If the plague ancestor resides in 20-million-year-old amber, it makes for a fascinating thread through time, tracing a devastating disease from its current, less-deadly incarnation all the way back into ancient history.
Poinar's findings were published in the Journal of Medical Entomology this month under the title "A New Genus of Fleas with Associated Microorganisms in Dominican Amber."