roundworm egg
A roundworm egg discovered at the Celtic site. University of Basel, IPAS

Two thousand-year-old intestinal parasite eggs have been unearthed at the site of a Celtic settlement in Switzerland.

The parasites included durable eggs of roundworms, whipworms, and liver flukes.

Archaeologists from the University of Basel discovered the parasites in samples taken from the former Celtic settlement of Basel-Gasfabrik - the present day site of Novartis.

The area was inhabited around 100 BCE and is one of the most significant Celtic sites in central Europe. Researchers say their finding suggests the community lived in very poor sanitary conditions.

Excrement of human or swine infested with roundworm (Ascaris sp.) and whipworm (Trichuris sp.). University of Basel, IPAS

Eggs were discovered in the backfill of ancient storage and cellar pits from the Iron Age.

They were discovered using a geoarchaeology method, which was applied to thin sections allowing the eggs to be captured in their original settings.

These sections were prepared from soil samples embedded in synthetic resin – meaning researchers could work out the exact location and number of the eggs at their original site in the sediment pits.

Findings of the study provide clues into the diseases triggered by parasites at the settlement and suggested the inhabitants lived in poor sanitary conditions.

Published in the Journal of Archaeological Science, researchers believe the parasites might have been brought into the settlement from the surrounding areas via livestock – at the time humans and animals lived side by side.

"The eggs of the Iron Age parasites originate from preserved human and animal excrement (coprolites) and show that some individuals were host to several parasites at the same time," the authors said.

"Furthermore, the parasite eggs were distributed throughout the former topsoil, which points to the waste management practiced for this special type of 'refuse'. It may, for example, have been used as fertilizer for the settlement's vegetable gardens."