In vitro efficacy of Quillaja saponaria extracts on the infective life-stage of ectoparasite Caligus rogercresseyi

The effect of two different commercial products of Quillaja saponaria saponin extract on mortality of the free-living copepodite stage sea-lice Caligus rogercresseyi were assessed in vitro. Parasites were exposed for 24 hr to different concentrations of Quillaja extracts and then observed until 30 hr in non-Quillaja media. The EC50 and EC90 were evaluated at 30 hr. High mortalities of copepodites were obtained at higher doses (500 ppm) for both extracts. Higher mortalities were obtained using the product with higher saponin content at 24 hr (23.3% vs. 86.6%) and 30 hr (63.3% vs. 93.3%) compared with the product containing less saponins. In addition, mortalities increased even after removing the extracts suggesting a residual and prolonged effect on the survival of the parasite. Our results indicated that the free-living stage of the parasite is sensitive to saponins from Q. saponaria extracts and may be used to control or prevent the infestation of C. rogercresseyi in salmonids in Chile.