A study of 2,500-year-old toilets in Jerusalem has revealed the oldest ever example of dysentery infecting humans.

Analysis of two latrines dating back to Iron Age Jerusalem has uncovered traces of a single-celled microorganism Giardia duodenalis – a common cause of dysentery, a debilitating infection of the intestines.

The research team led by University of Cambridge says it is the oldest example of the parasite infecting humans anywhere on the planet.

Lead author Piers Mitchell from Cambridge’s department of archaeology, said, “The fact that these parasites were present in sediment from two Iron Age Jerusalem cesspits suggests that dysentery was endemic in the Kingdom of Judah.

“Dysentery is spread by faeces contaminating drinking water or food and we suspected it could have been a big problem in early cities of the ancient Near East due to over-crowding, heat and flies and limited water available in the summer.”

The samples came from the sediment underneath two toilets found in building complexes excavated to the south of the Old City, which date back to the 7th century BCE when Jerusalem was a capital of Judah.

During this time, Judah was a vassal state under the control of the Assyrian Empire, which at its height stretched from the Levant to the Persian Gulf, incorporating much of modern-day Iran and Iraq. Jerusalem would have been a flourishing political and religious hub estimated to have had between 8,000 and 25,000 residents.

Both toilets had carved stone seats almost identical in design. One was from a lavishly decorated estate at Armon ha-Natziv, surrounded by an ornamental garden. The site, excavated in 2019, probably dates from the days of King Manasseh, a client king for the Assyrians who ruled for 50 years in the mid-7th century.

The site of the other toilet, known as the House of Ahiel, was a domestic building made up of seven rooms, housing an upper-class family at the time. Date of construction is hard to pin down, with some placing it around the 8th century BCE.

Mitchell said, “Toilets with cesspits from this time are relatively rare and were usually made only for the elite.”

Ancient medical texts describe diarrhoea affecting the populations of what is now the Near and Middle East. One example reads: “If a person eats bread and drinks beer and subsequently his stomach is colicky, he has cramps and has a flowing of the bowels, setu has gotten him”.

Mitchell said, “These early written sources do not provide causes of diarrhoea but they encourage us to apply modern techniques to investigate which pathogens might have been involved.

“We know for sure that Giardia was one of those infections responsible.”

The team investigated the decomposed samples by applying a bio-molecular technique in which antibodies bind onto the proteins uniquely produced by particular species of single-celled organisms.

This research was undertaken through a collaboration between the University of Cambridge, Tel Aviv University, and the Israel Antiquities Authority.