Medieval monks in Cambridge, England, were almost twice as likely to be infected with parasites as others in the city, according to a new study by university researchers. International Journal of Paleopathology.

During the study, archaeologists carefully compared soil samples from around the urns of adults buried in the Augustinian Friary between the 13th and 16th centuries with similar samples of townspeople buried in All Saints by the Castle Church between the 12th and 14th centuries.

Archaeologists have excavated the remains of monks buried in a former Augustinian friary in central Cambridge, UK.

To control for subsequent soil contamination from feces, the investigators also compared the amount of parasites found in soil samples from the pelvis with those from the skull and feet.

The remains of 19 monks and 25 local residents were compared, and the researchers found that 11 monks (58%) – but only 8 (32%) of the townspeople – were infected with worms. Archaeologists were able to confirm that the remains belonged to priests based on metal belt buckles found with the skeletons that were part of the order’s standard clothing.

The researchers ran soil samples through a series of microsieves to separate out particles too large or too small to be parasite eggs. The mesh sieves had pore sizes of 300 μm, 160 μm, and 20 μm. A 20-μm sieve would collect the parasites, which were then suspended in glycerol and placed on slides. The researchers counted the eggs and determined their species at 400x magnification.

The researchers developed criteria to confirm that an individual’s remains were indeed infected with parasites and not eggs from contaminated soil. They said it was the first time such criteria had been used to rule out false positives, using egg counts in the legs and head as controls for those in the pelvis. In addition to excluding false positives, the researchers acknowledged that these criteria probably led to some false negatives.

Lead author Piers Mitchell, MD, PhD, University of Cambridge Medscape Medical News This is “the first study in the world where we look at a monastic order and the general public in the same city to see if a difference in lifestyle actually makes a difference in your risk of getting a parasite infection.” He added, “We thought you might find similar results or lower parasite infestation in the Augustinians because they had the proper toilets and stuff,” but they found the opposite to be true.

The team found roundworm and whipworm eggs, but no hookworm or tapeworm. Hookworm eggs are more fragile than others, Mitchell said, and “potting soil from medieval city burials is not as large as cave-dried coprolites.”

He expected to have tapeworm eggs because, being an Augustinian priest, they “couldn’t eat meat for a few days, so they would eat fish. But this monastery, which was a friary inside the city, didn’t have its own fish ponds. As the country monasteries did…It seems they had fresh water. They bought sea fish, not fish, and they have it. In Europe, the fish tapeworm is in freshwater fish, but not in sea fish. He did not detect it.”

The researchers admitted they were surprised to find that Cambridge burial sites were dominated by parasites that are usually spread by poor sanitation. This was unexpected as the monastery had toilet blocks and hand washing facilities that ordinary workers did not have. Worms notwithstanding, previous research suggests that those buried in medieval English monasteries lived longer than townspeople buried in church cemeteries.

In addition to being a paleopathologist—a specialist in disease through the study of ancient fossils—Mitchell runs and teaches in an ancient parasite laboratory. In addition, he is a practicing pediatric orthopedist.

Int J Paleopathol. Published online 19 August 2022. Full text

Mitchell declares no relevant financial relationships.

Judy Stone, MD, is an infectious disease specialist and author Resilience: One Family’s Story of Hope and Triumph over Evil and Conducting Clinical Research , the ultimate guide to the subject. You can find it at drjudystone.com or on Twitter @drjudystone.