In Vitro Disinfection Efficacy Assay on Giardia duodenalis Cysts

Background: The cysts of the protozoan parasite Giardia duodenalis, which targets a broad spectrum of hosts including humans, can withstand environmental conditions for months, making effective disinfectant measures crucial for minimizing the infection burden. Previous investigations concerning disinfection efficacy were based on cysts from fecal/water samples or animal models, which are either unfit for standardized procedures or related to ethical concerns. Methods: To perform standardized in vitro disinfectant testing, four different encystation protocols were compared firstly. The protocol with the highest efficacy in our hands (1.7 × 105 cysts per tube) was used for the production of cysts to establish a disinfectant assay. Therefore, it was used for the production of cysts to establish a dis-infectant efficacy assay. After incubation with a commercial disinfectant (ViPiBaX Giardien Ex®) or 30% hydrogen peroxide solution (H2O2) at 10 °C and room temperature, parasite cyst viability was evaluated by the yield of trophozoites obtained by the applied excystation protocol. Results: Only untreated Giardia cysts, which were used as a negative con-trol, released trophozoites. The protocol established for the evaluation of cyst viability delivered reproducible results and appeared suitable for testing the inactivation of cysts by chemical disinfection. Conclusions: Under the given conditions, the disinfectant ViPiBaX Giardien Ex® and H2O2 inactivated Giardia cysts.