Université Bordeaux Montaigne, CNRS UMR 5607 Ausonius, France; Université de Bourgogne Franche-Comté, CNRS UMR 6249 Chrono-Environnement, France.
Université de Bourgogne Franche-Comté, CNRS UMR 6249 Chrono-Environnement, France.
Infect Genet Evol. 2021 Jun;90:104713. doi: 10.1016/j.meegid.2021.104713. Epub 2021 Jan 8.
The study of ancient parasites, named paleoparasitology, traditionally focused on microscopic eggs disseminated in past environments and archaeological structures by humans and other animals infested by gastrointestinal parasites. Since the development of paleogenetics in the early 1980s, few paleoparasitological studies have been based on the ancient DNA (aDNA) of parasites, although such studies have clearly proven their utility and reliability. In this paper, we describe our integrative approach for the paleoparasitological study of an ancient population from Florence in Italy, dated to the 4th-5th c. CE. The first stage consisted in the study of sediment samples from the pelvic area of 18 individuals under light microscopy. This allowed us to detect Ascarid-type eggs belonging very probably to the human-infesting roundworm Ascaris lumbricoides. Ten subsamples were selected corresponding to five individuals, and we extracted their whole DNA following sediment aDNA protocols. A targeted approach allowed us to detect two nematodes and one trematode aDNA fragments, namely Ascaris sp., Trichuris trichiura, and Dicrocoelium dendriticum. Among the five individuals tested for microscopic eggs and aDNA, three of them showed the remains of eggs (only Ascarid-type), but all of them tested positive to the presence of at least one parasite aDNA. Microscopic diagnosis first guided our research for the selection of promising samples while the targeted aDNA approach significantly improved our knowledge in terms of parasitic diversity and frequency in this population subgroup. These results enabled us to discuss the possible impact of latent parasitism in this past population at the time of an epidemic, as suggested in Florence. In particular, the singular case of D. dendriticum detection is discussed in light of the present-day scarcity of genuine human infections. Nevertheless, actual infections are known in the paleoparasitological record, and food habits may have led to false parasitism in this historical context. aDNA leaching from overlying strata may also explain this detection. This study strongly pleads for a systematic integrative approach combining microscopy and aDNA in paleoparasitology.
古寄生虫学的研究传统上集中在通过人类和其他受胃肠道寄生虫感染的动物传播到过去环境和考古结构中的微观卵。自 20 世纪 80 年代早期古遗传学的发展以来，尽管此类研究清楚地证明了它们的实用性和可靠性，但很少有古寄生虫学研究基于寄生虫的古代 DNA(aDNA)。在本文中，我们描述了我们对来自意大利佛罗伦萨的一个古代人群进行古寄生虫学研究的综合方法，该人群的年代可追溯到公元 4-5 世纪。第一阶段包括在显微镜下研究 18 个人的骨盆区域的沉积物样本。这使我们能够检测到非常可能属于人类寄生蛔虫的蛔虫型卵。选择了十个亚样本，对应于五个人，并按照沉积物 aDNA 方案提取了它们的全 DNA。靶向方法使我们能够检测到两个线虫和一个吸虫的 aDNA 片段，即蛔虫、鞭虫和树枝状双腔吸虫。在对显微镜下的卵和 aDNA 进行测试的五个人中，有三个人显示出卵的残留物（仅为蛔虫型），但所有人的至少一种寄生虫 aDNA 均呈阳性。显微镜诊断首先指导了我们对有希望的样本的研究，而靶向 aDNA 方法则大大提高了我们对该人群亚群中寄生虫多样性和频率的了解。这些结果使我们能够讨论在佛罗伦萨提出的流行时期该过去人群中潜在寄生虫感染的可能影响。特别是，在当前真正的人类感染罕见的情况下，讨论了树枝状双腔吸虫的检测情况。尽管在古寄生虫学记录中已知有实际感染，但在这种历史背景下，饮食习惯可能导致虚假感染。来自上覆地层的 aDNA 浸出也可能解释这种检测。这项研究强烈主张在古寄生虫学中采用系统的综合方法，将显微镜检查和 aDNA 结合起来。
