Molecular archaeoparasitology identifies cultural changes in the Medieval Era

Intestinal parasites have afflicted humans throughout history and remain common in parts of the developing world. Prior to today’s improvements in hygiene and medicine, gut parasites during the 18th century were prevalent throughout the world, which makes them an intriguing target for investigation of historical events. Previous molecular studies of historical infections have focused mostly on high-impact diseases (e.g. plague, leprosy, smallpox, malaria & tuberculosis); these studies typically fixated on one, or very few, samples from a site and were targeted largely towards identifying the pathogen being studied. However, such infectious disorders often cause acute disease, interfere with the daily lives of infected persons, and can be difficult to detect in archaeological contexts (if identification relies on analysis of mummified or skeletal remains).

In contrast, enteric worms (helminths) do not have devastating clinical effects; their eggs are readily detectable in a wide variety of archaeological contexts associated with human fecal material. “Helminths” is a collective term encompassing nematodes (roundworms), trematodes (flatworms), and cestodes (tapeworms). There are many examples in each group that infect a range of hosts, including humans. Some roundworms are transmitted via the fecal–oral route, whereas tapeworms enter humans when eating undercooked red meat or freshwater fish. Therefore, the type, and number, of eggs found in a fecal deposit can be used to interpret levels of hygiene and/or dietary habits. Authors previously have found that >95% of pre-18th century latrine and other communal deposit samples contain helminth eggs. The high prevalence of these helminths, their low pathogenicity, and robustness of eggs having ancient DNA that can be studied –– are features that can provide answers to historical and archaeological questions.

In the attached publication, authors integrated parasite studies with ancient DNA-sequencing, studying a large sample-set, dating between Neolithic and Early Modern periods, to explore the usefulness of molecular archaeoparasitology –– as a new approach to study History. Molecular analyses provided unequivocal species-level parasite identification and revealed location-specific epidemiological signatures. Roundworms (Ascaris lumbricoides and Trichuris trichiura) were discovered to be ubiquitous across time and space. By contrast, high numbers of tapeworms (Diphyllobothrium latum and Taenia saginata) were restricted to medieval Lübeck (major port city in northern Germany, which dates back to its being the medieval capital of the Hanseatic League, a powerful trading confederation).

The presence of these tapeworms, and changes in their prevalence at approximately 1300 A.D., indicate substantial alterations in diet or parasite availability. The tapeworm DNA sequences revealed two different groups: one ubiquitous; the other restricted to medieval Lübeck and Bristol (port city straddling the River Avon in southwest England, also having a rich maritime history). The high sequence diversity of this specific tapeworm DNA detected in Lübeck is consistent with its importance as a Hanseatic trading center. This study introduces the research field of molecular archaeoparasitology as an artefact-independent source of historical evidence.


Proc R Soc B, 2o18; 285: 20180991

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