NEW YORK (GenomeWeb) – Genetic analysis of a pilgrim who died in the late 11th or early 12th century showed that he was infected with Mycobacterium leprae belonging to the 2F lineage.
The University of Surrey’s Michael Taylor and his colleagues excavated the pilgrim and two other individuals for biomolecular, radiocarbon, and isotopic analysis. As they reported today in PLOS Neglected Tropical Diseases, they found that the pilgrim, a man between the ages of 18 and 25 years when he died, was likely not local to the area in Britain where he was buried and was infected with a leprosy strain now associated with south-central and western Asia.
“[T]hese results add to our understanding of isolates behind the widespread nature of European leprosy in the high Middle Ages and in particular of a rare lineage which is less common amongst extant strains,” the researchers wrote in their paper.
Taylor and his colleagues excavated three skeletons from burial grounds at St. Mary Magdalen in southern England, a known leprosarium. The skeleton focused on in this study was buried with a scallop shell indicating that he’d made a pilgrimage to the shrine of St. James in Spain.
Radiocarbon datingindicated that the pilgrim’s skeleton was from the late 11th or early 12th centuries, while the control skeletons dated to the 17th and 18th centuries. Only the pilgrim’s bones — and not those from the controls — exhibited evidence of leprosy, as he had lesions in his feet. The restriction of the lesions to his feet suggested to the researchers that he likely had greater soft tissue manifestations of the disease.
Isotope analysis suggested that the pilgrim ate a diet consisting of more animal protein than others buried in the cemetery, and it indicated that he was not native to the Winchester, UK, area where he was buried, but that he could be from another British locale. Analysis of his skull shape also suggested that he might not be of British origin.
Despite the pilgrim’s low bone signs of leprosy, the researchers were able to isolate M. leprae DNA from him for analysis. They first screened all three skeletons for signs of M. leprae using the multi-copy element RLEP, which they then confirmed by real-time PCR analysis of the multi-copy element IS1081. Only the pilgrim came back positive for M. leprae. The samples were also screened to determine whether they were infected with Brucella, Treponema pallidum, Burkholderia pseudomallei, Leishmania, Plasmodium, or hepatitis B virus, but none were.
Through a combination of SNP and VNTR typing, the researchers found that the pilgrim harbored leprosy belonging to the 2F strain, but one that is genetically distinct from others found at that site.
Most of the leprosy strains found at the cemetery belong to genotype 3I, which has homology with existing strains of this lineage, they noted. These are thought to be ancestral to strains now found in the southern US. The 2F genotype is also found at this site and today is found in central Asia and the Middle East. This suggests that settlers might’ve brought this strain to the region or that the pilgrim picked it up in his travels.
The researchers further noted that the M. leprae genome hasn’t changed much since the disease peaked in medieval Europe, which might account for the decrease in disease transmission.
“Further ancient genome analysis linked to population genetics can potentially provide important additional information on the genetic origin, but overall these findings confirm the benefits of a multidisciplinary approach which allows investigation of the wider relationship between leprosy, medieval pilgrimage, and M. leprae transmission,” the authors wrote.
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