Lifestyle and Intestinal Parasite Infection in Northern Europe: A Study Comparing Clergy and the General Population of Cambridge and Belgium in 12th-18th Centuries

Abstract

While parasites were widespread in medieval Europe, very little work has been undertaken to compare how the risk of contracting different species may vary with a person’s lifestyle. A range of intestinal parasites have been identified from medieval and early modern excavations in northern Europe including whipworm, roundworm, beef tapeworm, pork tapeworm, fish tapeworm, liver flukes, and protozoa that cause diarrhoea and dysentery. Some types of parasitic worm are contracted by the contamination of food and drink by faeces, but other parasites are caught by eating raw, smoked, pickled or salted meats or fish. People with limited sanitation and sewers, limited clean water, and limited washing might have been at higher risk of contracting parasites spread by faeces such as roundworm, whipworm and dysentery. Those eating raw, smoked, salted, pickled or undercooked meats and fish might have been at higher risk of infection by fish tapeworm, beef tapeworm and pork tapeworm. On top of this, the majority of the evidence for parasites in medieval Europe comes from communal contexts, such as latrines. Little is known on how common it was to have parasites in the past, as we have no idea how many people used those latrines. The major aim of this thesis is thus to explore how one’s lifestyle may have had an impact on the risk of parasite infections in medieval Europe, down to an individual level. To achieve this, I compared parasite infection conditions – both species type and prevalence – of the general European medieval population, with those leading specific lifestyles with different diets, such as the clergy. I analysed soil samples taken from pelvic region of skeletal remains using microscopy to determine which individuals were infected by intestinal parasites. Meaningful investigations – such as if parasitism is relevant to certain lesions, if parasites were more common in either sex, or whether age at death affected risk of parasite infections – are all explored by my research. Cesspit samples were analysed using microscopy to identify preserved parasite eggs and enzyme-linked immunosorbent assay (ELISA) for protozoan cysts. Evidence of parasites transmitted via the faecal-oral route – such as roundworm and whipworm – was found across all samples that produced positive results, despite varied egg counts and concentrations. In some cases these differences stemmed from genuine discrepancies in regard to hygiene practice and facilities; for others, this might have resulted from different conditions of taphonomy that had led to different preservation of parasite eggs. No evidence of zoonotic food-borne parasites – such as fish tapeworm, transmitted via consuming of undercooked freshwater fish – was found, even in regions where freshwater fish was known to be a major cooking ingredient. This suggests that fish was thoroughly cooked prior to consumption. In other places this might be due to a preference towards marine fish that does not transmit such parasites, which is consistent with isotopic evidence of marine resource consumption. Parasite infections are often associated with other factors, such as cribra orbitalia – a skeletal lesion commonly encountered in bioarchaeological investigations. It has been suggested that this is a causal relationship, hence the lesion can function as a proxy indicator for intestinal parasite infection. This study tests whether this hypothesis holds true in the medieval population of Cambridge. Since skeletal profiles of the sampled individual had been gathered in assessing cribra orbitalia, I also investigated if males or females were of higher parasite morbidity, negative association could be demonstrated. The research has deepened our understanding of parasite infections in medieval societies in the following ways: (1) We now know how common intestinal parasite infection was in medieval Cambridge and Ghent, and what species of parasites were prevalent. For Cambridge: parasites of faecal-oral route, i.e. roundworm and whipworm, were the only species found in both the Augustinian friars and the All Saints by the Castle parishioners. Interestingly, the infection rate in the fomer group, which was considered cleaner hence less inclined to suffer from such parasites, was nearly twice as high as that of the general population buried at the All Saints cemetery. For Ghent: similar to that at Cambridge, there was a marked dominance of parasites that are spread when sanitation is ineffective, namely roundworm, whipworm, the protozoa Giardia duodenalis, and Entamoeba histolytica. No notable difference in the species of parasites found in the clergy and general public was noted. (2) We now know how much – in our sample sets, at least – intestinal helminth infection is associated with skeletal lesions such as cribra orbitalia, and if the parasite infection conditions between males and females in Medieval Cambridge were similar. No association between infection and cribra orbitalia in this medieval adult population was found; no statistical difference in parasite infection between sexes was noted in the studied groups. (3) There appears to have been genuine differences in parasite infection patterns between monastic orders and general population in medieval Cambridge, albeit in direct contradiction to my original hypothesis: for all the advanced hygiene facilities the frairs had enjoyed, they had in fact manifested a higher parasite infection rate. This highlights not only how occupation and lifestyle can have an impact on parasite’s transmission, but also the significance of empirical research in investigating ancient health and disease. (4) The significance of taphonomy needs to be highlighted in palaeopathological studies, where absence of evidence cannot be used as evidence of absence. (5) We now have a better understanding of medieval quality of life can be illuminated from knowledge of the health consequences of parasites, as can other aspects of life such as food predilection, cookery preference, and effectiveness of hygiene facilities.