Human worm infections have, to a large extent, been eradicated in countries with high sanitary standards by preventing the fecal-oral transmission of infective eggs. It is possible to study parasite infections among past populations by retrieving and analyzing parasite eggs using paleoparasitological techniques such as morphological examination and molecular identification.
Hard-shelled parasite eggs can be recovered from the environment even after extended periods of time and they have shown to be excellent reservoirs of ancient DNA (aDNA). aDNA analysis has enabled identifying which species of parasite an egg originates from. This is impossible solely using morphological examination. One example is the whipworm, Trichuris spp. that is known to have narrow host ranges, which makes it particularly suited to determine from which host an egg originates.
A case study will be presented, in which parasite eggs from environmental samples collected at a Viking-age settlement (1018-1030 A.D.) are DNA typed to the species level. The human whipworm (Trichuris trichiura) and the human roundworm (Ascaris lumbricoides) are identified indicating that these parasites were endemic in Denmark in the Viking-age. Further, eggs of the Liver Fluke (Fasciola hepatica), whose primary hosts are cows and sheep, are identified indicating that grazing animals were kept in close proximity of the settlement.