The stomach-churning gardening habits of medieval friars left them riddled with more parasitic worms than the general population, archaeologists have found.

A new analysis of 12th to 14th century skeletons from an Augustinian friary in Cambridge found nearly six in 10 monks were infected with gut worms, compared with around one third of the townspeople.

Researchers from the University of Cambridge’s Department of Archaeology believe the difference in infection rates may be down to monks manuring crops in friary gardens with their own faeces, or purchasing fertiliser containing human or pig excrement.

The experts said they were surprised by the findings, because monasteries tended to be more hygienic than the houses of ordinary working people, often containing toilet blocks with running water and hand-washing stations, instead of communal cesspits.

“This is the first time anyone has attempted to work out how common parasites were in people following different lifestyles in the same medieval town,” said Dr Piers Mitchell, the study’s lead author.

“The friars of medieval Cambridge appear to have been riddled with parasites.”

Augustinian Friary with extra parasites

Cambridge archaeologists investigated samples of soil taken from around the pelvises of adult remains from the former cemetery of All Saints by the Castle parish, as well as from the grounds where the city’s Augustinian Friary once stood.

The friary in Cambridge was an international study house, where clergy from across Britain and Europe would come to read manuscripts.

It was founded in the 1280s and lasted until 1538 before being destroyed as part of Henry VIII’s break with the Roman Church.

Although the 32 per cent prevalence of parasites among townspeople is in line with studies of medieval burials in other European countries, the friary rates were found to be remarkably high.

The study suggests the actual numbers of infections may have been higher, but some traces of worm eggs in the pelvic sediment would have been destroyed over time by fungi and insects.

Wormwood and powdered moles

Researcher Tianyi Wang, who performed the microscopy to spot the parasite eggs, said: “Roundworm was the most common infection, but we found evidence for whipworm infection as well.”

As roundworm and whipworm are spread by poor sanitation, researchers argue that the difference in infection rates between the friars and the general population must have been due to how each group dealt with their human waste.

“One possibility is that the friars manured their vegetable gardens with human faeces, not unusual in the medieval period, and this may have led to repeated infection with the worms,” said Mitchell.

Medical books written by Cambridge doctors around the same time mention the worms, but thought they arose from phlegm or mucus, rather than poor hygiene. Cures included aloe or wormwood and even grinding moles into a powder to make a curative drink.

The study is published on Friday in the International Journal of Paleopathology.