After studying the fecal remains under a microscope, researchers found eggs for four different species of parasitic worms, roundworm (Ascaris lumbricoides), whipworm (Trichuris trichiura), tapeworm (Taenia sp.) and Chinese liver fluke (Clonorchis sinensis).
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The Chinese liver fluke was a particularly notable find for the researchers because the parasite needs wet, marshy areas to complete its life cycle, but the latrine was located in the Tamrin Basin, a dry region to which the liver fluke is not native. The closest endemic area for the liver fluke is in fact some 932 miles (1,500 kilometers) away in Dunhaung.
"Our study is the first to use archaeological evidence from a site on the Silk Road to demonstrate that travelers were taking infectious diseases with them over these huge distances," says study co-author Hui-Yuan Yeh.
The parasite lives in the liver of humans, mainly in bile ducts, and can produce up to 4,000 eggs per day for at least six months.
"If an infected person goes to the toilet in fresh water, these eggs gain entry to a suitable snail, which acts as the intermediate host," the researchers wrote.
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The parasite's life cycle continues with a second intermediate freshwater fish host.
"Infection occurs when people eat raw fluke-infested fish," study leader Mitchell told Discovery News.
The liver fluke's success meant misery for travelers infected by it. The parasite causes abdominal pain, diarrhea, jaundice and even liver cancer.
An ancient network of thoroughfares extending 4,000 miles and linking an immense area that stretched from Rome and Russia all the way across Persia (modern-day Iran) and Kazakhstan into eastern China, the Silk Road came to prominence during the Han Dynasty, from 202 B.C.-220 A.D.
At that time merchants, pilgrims, monks, soldiers and nomads began traveling between the East and West for economic and cultural exchange.
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Researchers have previously suggested that diseases such as bubonic plague and leprosy were carried by the ancient travelers along the trading route.
"However, these diseases could have spread between China and Europe via other routes, such as through India to the south, or Mongolia and Russia to the north," Mitchell said.
"Now we have proved for the first time that the Silk Road was responsible for the spread of infectious diseases," he said.
Rossella Lorenzi contributed to this report.