Saturday, October 1, 2022

Gardening with human manure may have left medieval friars ‘riddled’ with worms

Augustinian friars in medieval Cambridge were almost twice as likely as other townsfolk to be infected by intestinal parasites and their gardening practices may have been to blame.

Analysis of sediment excavated around the pelvises of skeletons from two burial grounds indicates that almost two-thirds of friars had roundworm infections at the time of their death, compared with one third of ordinary residents. One friar was also infected by whipworms.

The findings, based on microscopic study of eggs in the soil where the intestines once lay, came as a surprise to the team at the University of Cambridge’s Department of Archaeology. Roundworm and whipworm infections are spread via faecal-oral transmission yet most friaries had latrine blocks and hand-washing facilities, unlike the houses of most working people.

A roundworm egg from the study. Image: Cambridge Archaeological Unit

Dr Piers Mitchell, an expert in paleopathology and one of the study’s authors, said: “If we were going to have different prevalence, we thought the poor peasants would probably have higher parasite infection rates than the friars, who followed a rule where they had a much cleaner environment.”

He said the friars’ higher infection rate could be down to them having used their own faeces as manure in friary vegetable and herb gardens, or purchasing fertiliser containing human or pig excrement. “It was part of friary life to have vegetable gardens and for some friars to spend time tending them and using them to feed other friars. So it seems quite likely that that would be a way of of reinfecting everybody. Once a year a cesspit or latrine needed digging out. And instead of taking the waste out to farms outside town, which is what many people would have done, it may well be that the friars fertilised their own crops with it.”

The study, published in the International Journal of Paleopathology, is the first to compare parasite prevalence in people from the same medieval community who were living different lifestyles.

The population of medieval Cambridge consisted of residents of monasteries, friaries and nunneries of various Christian orders, alongsde merchants, traders, craftsmen, labourers, farmers, and staff and students at the university. The archaeologists investigated samples of soil taken from around the pelvises of adult remains from the former cemetery of All Saints by the Castle parish church, as well as from the grounds where the city’s Augustinian Friary once stood.

Sanitation in medieval towns relied on cesspits — holes in the ground used for faeces and household waste. In religious houses, however, running water systems were a common feature, including to rinse out latrines, although it is uncertain for now whether the partially excavated Cambridge site had this.

Most of the All Saints parish church burials date from the 12-14th centuries, and were of people of lower socio-economic status, including agricultural workers. The Augustinian friary in Cambridge was an international study house, known as a studium generale, where clergy from across Britain and Europe would come to read manuscripts. It was founded in the 1280s and lasted until 1538 before becoming a casualty of Henry VIII’s break with Rome.

Not all people buried in friaries were clergy, as wealthy people from the town could pay to be interred there. However, the team could tell which graves belonged to friars from the remains of their standard metal belt buckles.

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

Dr Piers Mitchell

The researchers tested the remains of 19 friars from the friary grounds and 25 locals from All Saints cemetery and found that 11 of the friars (58 per cent) were infected by worms, compared with eight of the general townspeople (32 per cent). They said these rates were likely the minimum, and that actual numbers of infections would have been higher as some traces of worm eggs in the pelvic sediment would have been destroyed over time by fungi and insects. 

The 32 per cent prevalence of parasites among townspeople is in line with studies of medieval burials in other European countries, suggesting this was not particularly low. On the other hand, the friars’ infection rate was remarkably high. “The friars of medieval Cambridge appear to have been riddled with parasites,” Mitchell said.

Dr Tianyi Wang, who carried out the microscopy to spot the parasite eggs, said: “Roundworm was the most common infection, but we found evidence for whipworm infection as well. These are both spread by poor sanitation.”

In the paper, the team explain that roundworm can reach up to 30cm in length, while whipworm are smaller, up to 5cm. Both worms have a lifespan of 1–2 years and, after mating, their eggs are passed in human faeces. The eggs are durable, surviving months or years in some soil conditions. Once faecal material containing infective eggs are ingested on food or in water, larvae hatch in the intestine. Whipworms mature in lining of the intestines, but immature roundworm migrate through the tissues to the lungs where they mature, crawl up the airways to the throat, and are swallowed back into the intestines where they develop into adult worms and mate in the intestines to produce their own eggs.

Mitchell said that worm infections may have led to unpleasant symptoms, such as abdominal pain, coughing or bloating, in some friars, but they were unlikely to have been dangerous. He said the infections are more worrying in children, when they may cause malnutrition, stunted growth and other problems.

A medieval Augustinian friar. Early 20th century illustration by FA Gasquet, public domain, via Wikimedia Commons

Medieval texts give insights into the ways in which medieval residents of Cambridge are likely to have understood and sought to treat such infections. John Stockton, a medical practitioner in Cambridge who died in 1361, left a manuscript to Peterhouse college that included a section De Lumbricis (“on worms”). It claims that intestinal worms are generated by excess of various kinds of phlegm: “Long round worms form from an excess of salt phlegm, short round worms from sour phlegm, while short and broad worms came from natural or sweet phlegm.”

The text prescribes “bitter medicinal plants” such as aloe and wormwood, but recommends they are disguised with “honey or other sweet things” to help the medicine go down.

Another text, Tabula medicine, found favour with leading Cambridge doctors of the 15th century, and suggests remedies as recommended by individual Franciscan monks, such as Symon Welles, who advocated mixing a powder made from moles into a curative drink.

Despite the Cambridge friars’ parasite problems, previous research indicates that those buried in medieval England’s religious institutions lived longer than those buried in parish cemeteries, perhaps due to their better diet. An earlier study from the Cambridge team indicates that Cambridge’s friars suffered a much higher prevalence of gout than other townsfolk. This may reflect a greater consumption of alcohol, meat and fish in spite of their vows of poverty.

Mitchell said future studies on other sites could reveal whether the friars of Cambridge were representative of members of religious communities in their prevalence of parasites, or an anomaly due to local practices.

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