A Bioarchaeological Study of the Impact of Mobility on the Transmission of Tuberculosis in Roman Britain

Abstract

Tuberculosis (TB) is an infectious disease mainly transmitted to humans by the inhalation of infected droplets (produced when an infected person coughs or sneezes). It is caused by bacteria within the Mycobacterium tuberculosis complex, several species of which can cause infection in humans. In the early 1990s, the World Health Organisation (WHO) declared TB a global emergency and this continues to be the case today. We seem to be further from eradicating this killer disease than we have been at any point in our past, and the increase in global travel, including migration, is thought to be exacerbating its spread.

Building on previous projects that extracted and analysed ancient DNA of M. tuberculosis complex organisms from skeletons with bone changes consistent with TB from the Roman period in Britain, this research tests the hypothesis that people buried in Roman Britain who were infected with TB had been mobile at some point in their lives, by the application of stable isotopic analysis (C, N, Sr, O) to the same skeletons to establish if their childhoods were local or non-local to their burial locations.

This study uses bone and dental samples from skeletons from the ancient DNA projects who were buried on chalk geology and with bone changes suggesting possible TB and/or a positive TB ancient DNA result. The sites investigated were Driffield Terrace in York, Baldock, Easington, Winchester, Cirencester and Poundbury. Collagen was successfully extracted from bone for 19 out of 21 individuals. Carbon and nitrogen isotope analysis revealed that all but three of these people ate a diet based on C3 terrestrial ecosystems with limited aquatic food intake, and they were similar to other people buried in the same or other contemporary cemeteries. Enamel from the teeth of all 21 individuals was also subject to strontium and oxygen isotope analysis, which identified six people as not having been brought up in the local area where they were buried. The remaining 15 people were possibly raised locally, although other places of origin have been considered.

It was concluded that linking mobility, as identified using stable isotope analysis, with transmission of infectious disease evidence in the skeleton is very challenging, particularly because there is no way of knowing how long people had been infected with the disease before or after they were mobile. Finally, some suggestions of how to take this important work forward were made. This includes repeating the work on an available larger sample size of possible TB sufferers without constraints of only testing those individuals buried on chalk geology.