Paleopathological Evidence and Detection of Mycobacterium leprae DNA from Archaeological Skeletal Remains of Nabe-kaburi (Head-Covered with Iron Pots) Burials in Japan

Aiko Saso,Keigo Hoshino,Yuko Ishido,Junya Sakurai,Kazunari Tanigawa,Yuqian Luo,Kazuaki Hirata,Shuichi Mori,Koichi Suzuki,Norihisa Ishii

doi:10.1371/journal.pone.0088356

Abstract

The Nabe-kaburi is a unique burial method, the purpose of which is shrouded in mystery. The burials were performed during the 15th to 18th centuries in eastern Japan, and involved covering the heads of the deceased with iron pots or mortars. The identification of leprosy-specific osteological lesions among some of the excavated remains has led to the suggestion that Nabe-kaburi burials were a reflection of the social stigma against certain infectious diseases, such as leprosy, tuberculosis or syphilis. However, molecular evidence for the presence of disease has been lacking. The goal of this study was to detect Mycobacterium leprae (M. leprae) DNA in archaeological human skeletal remains from Nabe-kaburi burials. The paleopathological data from three Nabe-kaburi burials were re-evaluated before small samples were taken from affected and control areas. DNA was extracted and used as a template to target the M. leprae-specific DNA using a combination of whole genome amplification, PCR analysis and DNA sequencing. M. leprae DNA fragments were detected in the two sets of skeletal remains that had also shown paleopathological evidence of leprosy. These findings provide definitive evidence that some of the Nabe-kaburi burials were performed for people affected by leprosy. Demonstration of the presence of M. leprae DNA, combined with archeological and anthropological examinations, will aid in solving the mystery of why Nabe-kaburi burials were performed in medieval Japan.

Highlights

The Nabe-kaburi burial was performed during the 15th to 18th centuries in the eastern region of Japan
Paleopathological characteristics of leprosy have been noted in some cases, there was no definitive evidence to prove that the skeletal remains belonged to persons who died with leprosy
Preservation of the bones was rather poor, highly sensitive whole genome amplification (WGA)-polymerase chain reaction (PCR) analysis and subsequent DNA sequencing clearly demonstrated that two cases were infected with M. leprae: one is TK6, excavated from the Tawara-ga-yatsu site, and the other is K48, excavated from the Usukubo site

Summary

Introduction

The Nabe-kaburi burial was performed during the 15th to 18th centuries in the eastern region of Japan. The deceased were buried with an iron pot or mortar covering their heads. A total of 105 Nabe-kaburi burials have been excavated in Japan [1]. There are two main theories in Japanese folklore as to why the deceased would be buried with iron pots on their heads [2,3]. The second reason is rather unique and somewhat humorous: Nabe-kaburi burials were performed for someone who died during the ‘‘Bon’’ period in Japan. The ‘‘Bon’’ is the Japanese ritual ceremony to welcome the souls of ancestors back from heaven during a 3-day period each summer. Relatives of the descendant might have been trying to protect the head of the deceased at burial

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