This finding confirms a public-health issue with potentially serious consequences whereby children can be exposed to an environment contaminated with food-and water-borne transmitted oocysts, and can hence become infected with C. cayetanensis.

Background: Giardia duodenalis causes giardiasis in humans, particularly in developing countries. Despite the availability of treatments, resistance to some of the commercial anti-Giardia drugs has been reported in addition to their harmful side effects. Therefore, novel treatments for giardiasis are required. In this study, we aimed to assess the in vitro activity of crude extracts of Ageratum conyzoides against G. duodenalis trophozoites. Methods: Plants were classified into three groups based on their flower colors: white (W), purple (P), and whitepurple (W-P). Plants were separately cut into leaf (L) and flower (F) parts. Changes in internal organelle morphology of trophozoites following exposure to crude extracts were assessed using transmission electron microscopy (TEM). In subsequent experiments, efficacy of the most active essential oils from crude extracts [half maximal inhibitory concentrations (IC 50) ≤ 100 μg/mL] against G. duodenalis trophozoites was tested. In vitro anti-Giardia assays using essential oils were performed in the same way as those performed using crude extracts. Results: LW-P and FP extracts showed high activity (IC 50 ≤ 100 μg/mL) against G. duodenalis trophozoites, with IC 50 ± SD values of 45.67 ± 0.51 and 96.00 ± 0.46 μg/mL, respectively. In subsequent experiments, IC 50 ± SD values of LW-P and FP essential oils were 35.00 ± 0.50 and 89.33 ± 0.41 μg/mL, respectively. TEM revealed the degeneration of flagella and ventral discs of G. duodenalis trophozoites following exposure to crude extracts. Conclusion: Crude LW-P and FP extracts of A. conyzoides showed the highest activity against G. duodenalis. Exposure to crude extract induced changes in the flagella and ventral discs of G. duodenalis trophozoites, which play important roles in attachment to the surface of mucosal cells. Our results suggest that the tested extracts warrant further research in terms of their efficacy and safety as giardiasis treatment.

Trichomoniasis is now an important health problem in developing countries. Although metronidazole has so far been widely used to treat this disease, the prevalence of metronidazole-resistant protozoa and unpleasant adverse effects have been found. In this study, natural products purified from Thai plants were, therefore, investigated for their effectiveness against Trichomonas vaginalis. The minimal inhibitory concentrations for all beta-glycosides against Trichomonas vaginalis at 24 h were in a range of 6.25-12.5 microM. In addition, torvoside A and H were found to be more potent than their corresponding aglycones, deglucosylated torvoside A and H, while other beta-glycosides were generally as active as their corresponding aglycones. The cytotoxicity of these compounds was also determined. Except for dalcochinin, none of the tested compounds showed cytotoxicity against Vero and cancer cell lines (KB and MCF-7), having IC(50) values greater than 50 microg/ml. In conclusion, beta-glycosides and several aglycones showed selective inhibition against Trichomonas vaginalis without harmful effect to mammalian cells.