The discovery of a Schistosomiasis parasite egg in a 6,200 year-old grave in Syria may be the earliest evidence that agricultural irrigation systems in the Middle East region contributed to a vast spread of disease. In a study published in the Lancet Infectious Diseases journal, scientists said it may have been spread by the introduction of crop irrigation in ancient Mesopotamia.
Schistosomiasis (also known as Bilharzia, snail fever, or Katayama fever) is caused by flatworm parasites that live in the blood vessels of the bladder and intestines. The infection can lead to anemia, kidney failure and bladder cancer.
The infection, in which the parasite burrows through the skin of people wading, washing or swimming in waters where it hides in freshwater snails, has become progressively more common over time and now causes a huge burden of disease across the world. According to the World Health Organization (WHO), Schistosomiasis affects almost 250 million people worldwide, and more than 700 million people live in endemic areas.
The discovery, at Tell Zeidan archaeological site in Syria, was made by a team of archaeologists and biological anthropologists working at The Cyprus Institute in Cyprus, Cambridge University in the UK, and the University of Chicago's Oriental Institute in the United States.
Dr Kirsi Lorentz of The Cyprus Institute, who leads the bioarchaeological investigation of human burials at Tell Zeidan, said that the egg was found in the pelvic area of the buried skeletonized body, where the intestines and bladder of the person would have been. ‘We took soil samples also from the head and foot areas of the grave to act as control samples and found they contained no parasitic eggs. This suggests the grave was not contaminated with the parasite more recently’, says Dr Lorentz.
The egg may be among the oldest evidence of man-made technology inadvertently causing disease outbreak. ‘The individual who contracted the parasite might have done so through the irrigation systems that were starting to be introduced in Mesopotamia around 7,500 years ago’ said Dr Piers Mitchell of Cambridge University, one of the co-authors of the paper. ‘The invention of irrigation was a major technological breakthrough, and yet, like any technology, it had unintended consequences and side effects. In fact, the development of civilization was very much a trade-off: more food, and a more reliable food supply, came at the cost of more disease’ explains Prof. Gil Stein, Director of the Oriental Institute, and another co-author of the study.
The oldest Schistosomiasis egg found previously was in 5,200-year-old Egyptian mummies. The parasite spends part of its life cycle in snails that live in warm fresh water, before leaving the snail to burrow through the skin of people in the water. People of all ages are at risk, and following infection suffer from anemia that significantly decreases physical productivity, as well as potentially from seriously debilitating, and even terminal conditions such as kidney failure and bladder cancer.
‘The individual infected with Schistosomiasis at Tell Zeidan was only around one year of age at death’ said Dr Lorentz. In rural areas of contemporary Gabon more than 80% of the children have the disease. WHO continues its efforts to combat the disease world wide.
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