Testing new parasite egg extraction methods in paleoparasitology and an attempt at quantification

• Our aim is to standardize egg extraction methods in paleoparasitology.
• Several combinations of acids and bases were tested.
• Sodium hydroxide seems to damage parasite eggs.
• Acids reduce non-parasite elements and biodiversity.
• RHM protocol was the best compromise between biodiversity and egg concentration.

In order to improve paleoparasitological analyses, we tested different acid (hydrochloric and hydrofluoric acids) and base (sodium hydroxide) combinations for parasite egg extraction in archaeological sediments. We used a method of egg counting to compare these results to those obtained with the standard paleo-parasitological RHM extraction protocol (rehydration–homogenization–micro-sieving). Tests show that the use of hydrochloric acid results in a concentration of some taxa like Ascaris sp. or Trichuris sp. and an appreciable decrease in vegetal and mineral remains. However, tests also show that acid use systematically decreases parasite species identified, as compared to the standard RHM protocol. Base use yielded even more negative results with systematically lower biodiversity than with the standard protocol, probably due to chemical processes on chitin contained in the eggshell. These results suggest acids and sodium hydroxide should be used as little as possible during extraction due to the damages they cause to the eggs of some parasite species. The counting method was an efficient technique with which to demonstrate our results and could be used in future paleoparasitology studies.