Mesopotamian Irrigation May Have Helped Out a Parasite That Now Infects 200 Million People

A parasite egg found in a grave in the Middle East gives scientists a window into how disease spread in prehistory

Male and female parasitic worms of the genus Schistosoma Science Picture Co./Corbis

Today, more than 200 million people worldwide are infected with the parasitic worms that cause schistosomiasis. But where did the disease come from? Researchers think that they might have found a clue in a 6,200-year-old grave in Syria.

In a new study published in the Lancet Infectious Diseases, researchers found that thousands of years ago, parasites might have gotten a helping hand from humans. 

During an archaeological dig at the grave site, the researchers identified the egg by painstakingly sifting soil from the pelvic area of the buried body. The parasites that cause schistosomiasis live in freshwater. The larvae use snails as a host for a while, but then enter the water in search of other, more appealing hosts—like humans. When they come in contact with a human host, these tiny worms burrow inside the flesh until they get to the blood vessels, where they grow and reproduce. The eggs from the parasite leave the body through the pelvic area.

Freshwater isn’t exactly common in Syria, but pollen found near the body suggests that water-dependent crops were being grown in the area—more than likely with irrigation. And while the technological breakthrough of irrigation may have lead to improvements in the amount of food available, it may have also lead to a more friendly environment for parasites.

“These irrigation systems distributed water to crops and may have triggered the beginning of the enormous disease burden that schistosomiasis has caused over the past 6000 years,”co-author of the study Piers Mitchell said in a press release.

People infected with schistosomiasis can suffer from abdominal pain, anemia, and even bladder cancer. Treatments do exist, but because this disease disproportionately affects the poor, treatment for the infected is often difficult to come by

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