Ancient skeleton shows leprosy may have spread to Britain from Scandinavia
Scientific studies of a 1500 year old skeleton from England have revealed new insights into the early spread of leprosy.
The skeleton comes from an archaeological excavation in Great Chesterford, Essex, eastern England. An international scientific team, led by Dr Sarah Inskip of Leiden University, and including researchers from Historic England, and the Universities of Birmingham, Southampton, Surrey, and Swansea examined the burial. The bones were of a man who was probably in his twenties when he died, sometime in the 5th or 6th centuries AD, and showed changes consistent with leprosy, suggesting that here was a very early British case of the disease.
Although leprosy is nowadays a tropical disease, in the past it occurred in Europe. Human migrations probably helped spread the disease, and there are cases in early skeletons from western Europe, particularly from the 7th century AD onward. However the origins of these ancient cases are poorly understood. The study of the Great Chesterford skeleton provided an important opportunity to shed light on the early spread of the disease.
Although the bones showed alterations that were suggestive of leprosy, as Dr Sonia Zakrzewski of the University of Southampton explains, this was not enough to provide a clear diagnosis:
“Not all cases of leprosy can be identified by changes to the skeleton. Some cases of leprosy may leave no trace on the bones; others will affect bones in a similar way to other diseases. In these cases the only way to be sure is to use DNA fingerprinting, or other chemical markers characteristic of the leprosy bacillus.”
Therefore, the bones were analysed for bacterial DNA and lipid biomarkers. The results not only confirmed the diagnosis of leprosy, but also allowed detailed genetic study of the bacteria that caused the man’s disease.
Professor Mike Taylor, a Bioarchaeologist from the University of Surrey, says “Not every excavation yields good quality DNA, but in this case, leprosy DNA isolated from the skeleton was so good it enabled us to identify its strain. The leprosy strain was shown to belong to the 3I lineage. This lineage has previously been found in burials from Medieval Scandinavia and southern Britain. However, the strain in burial GC96 appears to be earlier than those. Interestingly, the 3I lineage still persists to the present day and is found in some southern states of the USA, where it is responsible for disease in wild nine-banded armadillos and sometimes infects humans in contact with these animals.”
The identification of fatty molecules (lipids) from the bacteria confirmed the DNA results and also showed it was different from later strains. Emeritus scientist David Minnikin, from the University of Birmingham, says “With Leverhulme Trust support, we recorded strong profiles of fatty acid lipid biomarkers that confirmed the presence of leprosy. However, one class of the lipid biomarkers had distinct profiles that may distinguish these older leprosy cases from later Medieval examples.”
Isotopes from the man’s teeth showed that he probably did not come from Britain, but more likely grew up elsewhere in northern Europe, perhaps southern Scandinavia, matching the results of the DNA. This raises the intriguing possibility that he brought a Scandinavian strain of the leprosy bacterium with him when he migrated to Britain.
The results of their study are now published in PLOS ONE
Dr Sarah Inskip, says “The radiocarbon date confirms this is one of the earliest cases in the UK to have been successfully studied with modern biomolecular methods. This is exciting both for archaeologists and for microbiologists. It helps us understand the spread of disease in the past, and also the evolution of different strains of disease, which might help us fight them in the future. We plan to carry out similar studies on skeletons from different locations to build up a more complete picture of the origins and early spread of this disease.”