Leprosy is a fascinating disease- not just for its effects, but for the social implications of having the disease. Leprosy was an epidemic disease that not only infected millions of people over a span of thousands of years, but it still remains a threat in Third World countries. Due to its destructive effects on those infected, leprosy created a history of fear and segregation caused by misconceptions and rumor. In the United Kingdom, during the Middles Ages, 1050 to 1550 CE, leprosy reached its highest prevalence. In the mid-twelfth century alone it is estimated that there were 1.5 million cases of leprosy in England and Scotland. While we know quite a bit about what the disease does to people and the social effects of having leprosy, little is known about the demography of those who had the disease. Who was more likely to get leprosy? Did it change fertility? How long did they live once they got the disease? How do these factors effect the longevity of the disease itself? In order to really understand leprosy in the past, we need to know who it was happening to and how it changed their lives.
A new article by Blondiaux et al. (2015) examines the demographic structure of the leprosarium of Saint-Thomas d’Aizier, and compare it against other samples from similar sites. The Saint-Thomas collection includes 186 adults and 24 subadults, that were excavated as both individual burials and commingled remains (bone mixed together). They identified 70 males and 55 females, with the remaining individuals being indeterminate due to age or preservation. The comparative sample includes 1519 individuals from 8 medieval cemeteries where no leprosy was found. All nine of the sites under examination date from the Late Antique (450 AD) to Late Middle Ages (1300 AD), and were selected due to the extensive excavations of each site and overall good bone preservation. To compare differences in population structure between the general and leprosarium populations, two things need to be determined: 1) do they have leprosy? and 2) what age are they when they died?
Diagnosis of leprosy in skeletal populations is done based on the patterns of pathological damage done to the skeleton. Changes in the skull consist of erosion of the facial bones, loss of bone and teeth in the jaw, inflammation and remodeling of the nasal cavity, and general destruction of bone. The rest of the skeleton shows evidence of irregular bone formation due to damage and healing of lesions, and general infection. Leprosy also causes nerve damage, which leads to loss of fingers and toes.
In order to determine age of the individuals at each site, Blondiaux et al. (2015) used the cementochronology method. As discussed in the morbid terminology post on the subject, cementochronology is the study of cementum in the teeth to determine the age at death of an individual. Cementum is one of the four tissues that support teeth in the jaw. Each year, cementum forms as a light and dark band surrounding the tooth root that can be seen under a microscope. Similar to counting the lines in a tree, we can count the number of lines in the tooth cementum by adding the average age of tooth eruption to the number of lines seen.
Based on comparison of the ages of populations with and without leprosy, they found some interesting patterns. Those populations without leprosy survived and lived longer than those with leprosy, but females in particular had increased mortality. Recent clinical studies of leprosy showed that people with this disease were more susceptible to tuberculosis and cancer, and this may explain the increased mortality. However, there is no evidence that tuberculosis was more common in the women of the Saint-Thomas d’Aizier leprosarium, and it seems to be endemic to this group. One possible reason for increased female mortality may have been due to more general female mortality caused by death during childbirth. One of the burials found at Saint-Thomas d’Aizier includes a young pregnant woman, the fetus still in utero, and may support the hypothesis that these women who were segregated from society for leprosy may have died younger due to a lack of support and proper care during pregnancy.
Blondiaux et al. (2015) conclude that a possible cause for the decline in leprosy was due to infertility of those within the leprosaria. It is known that male fertility declines with leprosy, and if women were more likely to die during pregnancy, this would cause the population that was susceptible to the disease to decline over time. By comparing the ages of populations with and without leprosy, Blondiaux et al. (2015) are able to learn a little more about those effected by leprosy. Cementochronology allowed for more accurate age comparison of the individuals, and is providing more detailed information about past populations.
Blondiaux, J., Naji, S., Bocquet-Appel, J., Colard, T., de Broucker, A., & de Seréville-Niel, C. (2015). The leprosarium of Saint-Thomas d’Aizier: The cementochronological proof of the medieval decline of Hansen disease in Europe? International Journal of Paleopathology DOI: 10.1016/j.ijpp.2015.02.005