Personal hygiene sticks excavated from a 2,000-year-old latrine pit have preserved evidence of the transmission route for infectious diseases
Travellers on the Silk Road, the most famous trade route of the ancient world, were bringing more than the precious fabric with them out of China. Some bamboo sticks with scraps of grimy cloth wound around them have been identified as bottom wipers from a latrine pit in a 2,000-year-old Chinese relay station on the Silk Road. They have also preserved the first solid evidence of disease spread from east to west by travellers.
Samples of ancient faeces scraped off the fabric and brought back to a laboratory in Cambridge have revealed eggs from four species of parasites, including Chinese liver fluke. The fluke needs marshy conditions to complete its life cycle, so could not have come from the desert area around the ancient Xuanquanzhi relay station.
The Chinese liver fluke originated thousands of miles away from the arid Tamrin Basin, an area including the Taklamakan Desert – one of the harshest on earth, dubbed the desert of death by the Chinese. 2,000 years ago the parasites unfortunate host would have been a very unhappy traveller, producing symptoms including fever, griping pain, diarrhoea and jaundice. It has also been associated with some forms of cancer.
The relay stations at oasis towns, where travellers could rest and buy food, were crucial for any traders on the Silk Road hoping to survive the desert crossing.The bone dry conditions at these sites have preserved a wealth of organic remains for archaeologists.
The large Xuanquanzhi station was excavated just over 20 years ago. It has been dated to the Han dynasty, and was in use between 111BC to 109 AD. The most celebrated finds from the site are fragments of letters and other documents – including some written on silk – but it was the bamboo sticks wound with strips of fabric, used once and then thrown into the latrine pit, which excited Hui-Yuan Yeh, a researcher at Cambridge University.
The sticks had been stored carefully, but not judged worthy of further research. Hui-Yuan got permission to take some samples and bring them back to Piers Mitchell, an expert in ancient diseases at Cambridge who is the happy recipient of faecal samples sent to him from sites all over the world.
The two publish their findings on what are politely styled personal hygiene sticks this week in the Journal of Archaeological Science: Reports. They found roundworm, whipworm, tapeworm – and the Chinese liver fluke, whose nearest endemic area is around 1,500 km away, though the particular species is most common even further away, in Guandong Province, approximately 2,000 km from the site.
When I first saw the Chinese liver fluke egg down the microscope, I knew that we had made a momentous discovery, Hui-Yuan said. Our study is the first to use archaeological evidence from a site on the Silk Road to demonstrate that travellers were taking infectious diseases with them over these huge distances.
Mitchell said that while it had been suggested that the merchants, soldiers and government officials travelling along the route into the Middle East and on to the Mediterranean could have brought infections with them, there had never been any solid proof. The transmission route for diseases including bubonic plague, anthrax and leprosy, could instead have been through India, or by Mongolia and Russia to the north.
Now for the first time we know that liver fluke definitely did come along the Silk Road, and if so, we can assume that other diseases came by the same route. Its always nice to have proof, Mitchell said.