Trichomoniasis is a sexually transmitted disease (STD) caused by a small organism called Trichomonas vaginalis. Women are most often affected by this disease, although men can become infected and pass the infection on to their partners through sexual contact. Symptoms of infection in women include vaginal itching, a greenish-yellow frothy discharge with a foul odor, and discomfort during intercourse. Men often don't have symptoms of trichomoniasis, but when symptoms do occur, they include irritation inside the penis, mild discharge, and slight burning after urination or ejaculation. Treatment usually includes an oral antibiotic called metronidazole. Follow the links below to find WebMD's comprehensive coverage about how trichomoniasis is contracted, what it looks like, how to treat it, and much more.