The Silk Road was the ancient pathway that gained prominence around 200 BCE, spanning from the Far East to Europe, where travelers trekked to exchange silk, ivory, gold, silver, jade, tea, and opium. It opened up corners of the world to each other, spawned legends, and spread cultures. But that wasn't all they were spreading. Poop found on the route is now providing hard evidence that these travelers were also passing nasty parasites along with their luxury goods.

Cambridge researchers Hui-Yuan Yeh and Piers Mitchell used microscopy to study preserved poop from an area that was once a communal toilet spot in Xuanquanzhi, a kind of ancient rest stop found in the arid Tamrin Basin, not far from the Taklamakan Desert. The poop was taken from bits of cloth that were wrapped around wooden sticks that the researchers are calling “personal hygiene sticks.”

The samples of feces were shown to contain eggs from at least four species of parasitic worm: roundworm, whipworm, tapeworm, and – most importantly – Chinese liver fluke.

The Chinese liver fluke (Clonorchis sinensis) is a parasitic flatworm that causes abdominal pain, diarrhea, jaundice, and is even linked to liver cancer. To complete its lifecycle, it requires wet and marshy areas of land – nothing like the sandy, baron dunes of Xuanquanzhi. As such, it provides strong evidence that unfortunate travelers were harboring the disease while making journeys between China, across the Middle East, and to the Mediterranean.

"When I first saw the Chinese liver fluke egg down the microscope I knew that we had made a momentous discovery," Hui-Yuan Yeh, one of the study's authors, said in a press release.

Mitchell, the study’s lead author, added: “Finding evidence for this species in the latrine indicates that a traveler had come here from a region of China with plenty of water, where the parasite was endemic.”

In addition to Chinese liver fluke, previous studies have suggested that bubonic plague, anthrax, and leprosy may have been spread across the globe from east to west through this route. With this new solid evidence, that appears even more likely.

Mitchell concluded: "Until now there has been no proof that the Silk Road was responsible for the spread of infectious diseases. They could instead have spread between China and Europe via India to the south, or via Mongolia and Russia to the north… This proves for the first time that travelers along the Silk Road really were responsible for the spread of infectious disease along this route in the past."

^{The widespread route of the Silk Road. Red is the land route and blue is the sea/water route. Image credit: NASA/Goddard Space Flight Center. Edited by Splette/Wikimedia Commons. Public Domain}