Leprosy in medieval Denmark: Exploring life histories through a multi-tissue and multi-isotopic approach

By focusing on two Danish leprosaria (Naestved and Odense; 13th-16th c. CE) and using diet and origin as proxies, we follow a multi-isotopic approach to reconstruct life histories of patients and investigate how leprosy affected both institutionalized individuals and the medieval Danish community as a whole.

We combine archaeology, historical sources, biological anthropology, isotopic analyses (δ¹³ C, δ¹⁵ N, δ³⁴ S, ⁸⁷ Sr/⁸⁶ Sr) and radiocarbon dating, and further analyze bones with different turnover rates (ribs and long bones).

The δ¹³ C, δ¹⁵ N and δ³⁴ S results indicate a C₃ terrestrial diet with small contributions of marine protein for leprosy patients and individuals from other medieval Danish sites. A similar diet is seen through time, between males and females, and patients with and without changes on facial bones. The isotopic comparison between ribs and long bones reveals no significant dietary change. The δ³⁴ S and ⁸⁷ Sr/⁸⁶ Sr results suggest that patients were local to the regions of the leprosaria. Moreover, the radiocarbon dates show a mere 50% agreement with the arm position dating method used in Denmark.

A local origin for the leprosy patients is in line with historical evidence, unlike the small dietary contribution of marine protein. Although only 10% of the analyzed individuals have rib/long bone offsets that undoubtedly show a dietary shift, the data appear to reveal a pattern for 25 individuals (out of 50), with elevated δ¹³ C and/or δ¹⁵ N values in the ribs compared to the long bones, which points toward a communal type of diet and reveals organizational aspects of the institution.