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INTRODUCTION
Paleoparasitology is the parasitological study of ancient samples recovered at archaeological sites. For the past several decades, a significant body of paleoparasitological research has elucidated the patterns of parasitic infection in ancient societies worldwide, which information could not easily have been obtained by any other means.123 Briefly, ancient Ascaris eggs discovered at an archaeological site in Grand Grotte, France could be traced back to 30,000 years BP.4 Also, several-thousand-year-old Trichuris eggs have been found in the samples obtained from Kruger Cave in South Africa.5 Indeed, the findings of ancient intestinal parasite eggs have been reported at a great variety of archaeological sites all over the world.6
In Korea too, the reports on ancient samples from various archaeological sites have been forthcoming. For example, parasitologists have confirmed that pre-20th century Korean populations were seriously infected by different kinds of parasites.7891011 Most of these investigations have been made on the fecal samples from Joseon period (1392–1910 CE) mummies3 or soil-sediment samples of the geological strata of various archaeological sites.12
As for ancient tombs, however, especially Silla cases dating to or before the Three Kingdoms in Korean history, there have been very few parasitological reports. Considering Korea's long and intricately documented history, this data gap in the paleoparasitological records is disappointing. Therefore, the current report might particularly be meaningful to the researchers because it is the first-ever parasitological confirmation of the presence of ancient parasite eggs in a tomb dating to the Silla Dynasty prior to the 676 CE unification of the Korean peninsula.
CASE DESCRIPTION
In 2013, the Silla Cultural Heritage Research Institute investigated an archaeological excavation site at Gyo-dong, Gyeongju, Korea. The investigation had been officially permitted by the Cultural Heritage Administration of Korea (approval number: 2013-0285). In the course of the excavation, a Mokgwakmyo tomb (wooden chamber tomb) was discovered, within which a wooden coffin contained a number of human skeletons (Fig. 1A). The archaeological and anthropological progress on this case is summarized in our previous report.13
Fig. 1
Archaeological site at Gyo-dong, Gyeongju, Gyeongsangbuk-do province of Korea. (A) Sixth century Silla Mokgwakmyo tomb could be identified in the site. Human bones and multiple cultural remains could be also found within the coffin. (B) The soil-organic material precipitates were collected from the Hp or sacrum (indicated by asterisk).
Hp = hip bones.
Analysis of cultural relics found within the coffin dated the tomb's construction to about the sixth century, thus locating it to the Three Kingdom era (57 BCE–668 CE) in Korean history. Soil and organic-material precipitates on the hipbones and sacrum were collected for a detailed parasitological examination (Fig. 1B).
Each soil and organic-material specimen (1–4 grams) was rehydrated in 0.5% trisodium phosphate solution with continuous shaking,14151617 filtered through multiple-layered gauze, and precipitated for one day. The precipitate thus obtained was re-dissolved in 0.5% trisodium phosphate solution (final volume, 20 mL). Solution slides of all of the specimens subsequently were examined under light microscopy (BH-2; Olympus, Tokyo, Japan).
In the samples (total, 200 µL; 20 µL each time; 10 times), we identified ancient Ascaris lumbricoides and Trichuris trichiura eggs (Fig. 2). The measured dimensions (mean ± standard deviation) of the Ascaris and Trichuris eggs were 58.5 ± 2.8 (55.0–65.0) × 47.6 ± 2.9 (45.0–52.5) µm and 50.1 ± 0.7 (49.0–51.2) × 24.1 ± 0.9 (23.0–26.0) µm, respectively. The numbers of eggs per gram (EPG) ranged between 46.6 and 48.3 (Ascaris) and 32.8 and 62.1 (Trichuris) (Table 1).
Fig. 2
Ancient parasite eggs observed in the sixth century Silla Mokgwakmyo tomb samples. (A) Ascaris lumbricoides and (B) Trichuris trichiura eggs were found. Scale bars = 20 µm.
Table 1
Results of paleoparasitological examinations in this study
DISCUSSION
In previous parasitological studies on archaeological specimens, we were able to partially reconstruct the parasite-infection prevalence patterns among pre-20th century Korean populations. For instance, the examinations of fecal samples obtained from Joseon mummies yielded ancient Ascaris, Trichuris, Clonorchis, Paragonimus, and Metagonimus spp. eggs.3 According to our forthcoming series of reports, the overall Ascaris- and Trichuris-positivity rates during the Joseon Dynasty were 58.3 and 83.3%, respectively.18
Data obtained from Joseon mummy fecal samples, particularly in comparison with 20th century national survey data on parasitic infection in Korea, can significantly further our understanding of parasitism in pre-20th century Joseon society. Interestingly, historical rates of soil-transmitted parasitic infection in Korea did not markedly differ until the late 20th century (54.9% for Ascaris, 65.4% for Trichuris: national survey of 1971).3,19
As for the parasite-infection patterns prevailing prior to the Joseon period, however, the data remain scanty. In our previous paleoparasitological studies on samples obtained from archaeological sites representative of the Three Kingdom period or earlier, our positive findings on ancient parasite eggs were mostly confined to the soil samples of geological strata at ancient moats, reservoirs, or shell-middens.3 Such findings, though certainly suggestive of excreta origins, do not constitute any direct evidence of parasitic infection among Silla people. In this regard, the current examinations of soil and organic-material precipitate samples from the sixth century Silla Mokgwakmyo tomb can be considered integral to the researchers' efforts to reconstruct a complete, Korean-history-wide parasite-infection pattern.
Our discovery of Ascaris and Trichuris spp. eggs is the earliest among the ancient tombs for which we have found positive paleoparasitological results thus far. Since the individual found within the coffin was, judging from the status of the accompanying cultural remains, a member of the lower Silla nobility,13 this report also can be the first direct evidence of soil-transmitted parasitic infection among Three Kingdom period nobility. Considering the life cycle of soil-transmitted parasites, this means that even Silla nobles might have ingested foods or contacted soils seriously contaminated by human feces or derivative materials. Indeed, our parasitological analyses of archaeological samples from a variety of chronological eras can move us even closer to the goal of elucidating the parasitological infection patterns spanning Korean history.
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