Abstract: 　Objective To observe the effect of dihydroartemisinin(DHA) on the ultrastructure of Trichomonas vaginalis cultured in vitro. Methods The trophozoites of T.vaginalis were cultivated with liver extract solution medium containing 1 mg/ml dihydroartemisinin, and were then observed by scanning and transmission electron microscopes after the treatment for 2.5-4.0 h. Results The cell membranes of the trophozoites treated with DHA were damaged considerably. The surface of T.vaginalis showed deepening folds， hollow， and cracks. The nuclear membrane appeared fractures. There were a few of crevices in the nucleus and cytoplasm. Disordered and dilated endoplasmic reticulum, injured and deformed hydrogenosomes were found. Cytoplasm of the damaged parasites spilled over from torn place. After the cell membrane was peeled off, the nuclei, hydrogenosomes and pelta were exposed, which finally resulted in the death of the denatured parasites. Conclusion Dihydroartemisinin can destroy membrane structure and organelles of Trichomonas vaginalis trophozoites, which leads to decomposition and necrosis of the parasites.

Key words: Trichomonas vaginalis, Dihydroartemisinin, Ultrastructure, Scanning electron microscope, Transmission electron microscope