Recovering parasites from mummies and coprolites: an epidemiological approach

Abstract

In the field of archaeological parasitology, researchers have long documented the distribution of parasites in archaeological time and space through the analysis of coprolites and human remains. This area of research defined the origin and migration of parasites through presence/absence studies. By the end of the 20th century, the field of pathoecology had emerged as researchers developed an interest in the ancient ecology of parasite transmission. Supporting studies were conducted to establish the relationships between parasites and humans, including cultural, subsistence, and ecological reconstructions. Parasite prevalence data were collected to infer the impact of parasitism on human health. In the last few decades, a paleoepidemiological approach has emerged with a focus on applying statistical techniques for quantification. The application of egg per gram (EPG) quantification methods provide data about parasites' prevalence in ancient populations and also identify the pathological potential that parasitism presented in different time periods and geographic places. Herein, we compare the methods used in several laboratories for reporting parasite prevalence and EPG quantification. We present newer quantification methods to explore patterns of parasite overdispersion among ancient people. These new methods will be able to produce more realistic measures of parasite infections among people of the past. These measures allow researchers to compare epidemiological patterns in both ancient and modern populations.

Keywords: Coprolite; Epidemiology; Overdispersion; Parasite; Quantification.

Fig. 1

Graph derived from three examples of endoparasite overdispersion [23, 24]. Example A, a more marginal example of aggregation shows data for tapeworm infection (Triaenophorus nodulosus) in perch (Perca fluviatilis). In this example 54% of the tapeworms were in 18.5% of hosts with 81.5% uninfected or lightly infected. Example B shows pronounced overdispersion of the nematode (Porrocaecum ensicaudatum) in starlings (Sturnus vulgaris). In this case, 89% of the hosts are uninfected or lightly infected, and 69% of the parasites were recorded in 11% of the hosts. Example C shows a very pronounced case of overdispersion for nematodes (Spiroxys japonica) in pond frogs (Rana nigromaculata). In this case, 70% of the parasites were recorded in just 4% of the hosts while 88% of the hosts were uninfected and 8% had light infections.

Fig. 2

Graph derived on pinworm eggs recovered from La Cueva de los Muertos Chiquitos coprolites [26]. The graph exemplifies pronounced overdispersion with 66 of 100 samples negative. The ten samples with the highest counts contained 76% of the eggs. This is most similar to example C in Fig. 1

Fig. 3

Graph derived from pinworm infection data from Korean school children [27] (Fig. 1, trial 2). The data were collected in several anthelmintic “dewormings”. One of three treatments revealed a dispersed, negative binomial distribution: 72% of the worms were recovered in 13% of the subjects while 53% were uninfected