Trichomonas vaginalis, an anaerobic, parasitic flagellated protozoan,'s the causative agent of trichomoniasis, and's the most common pathogenic protozoan infection of humans in industrialized countries. The WHO has estimated that 180 million cases of infection are acquired annually worldwide. The estimates for North America alone are between 5 and 8 million new infections each year, with an estimated rate of asymptomatic cases as high as 50%. Clinical Trichomoniasis's a sexually transmitted inf… (More on Trichomonas)