What is trichomoniasis? Trichomoniasis is a sexually transmitted disease caused by infection with the protozoan Trichomonas vaginalis. In women this parasite infects the vagina; in men the epididymis, prostate or bladder can be involved. In the United States, the highest number of cases occur in women between ages 16 and 35. The disease is quickly and easily treated if diagnosed early, but left untreated it can lead to serious complications. Trichomonas infection is very common, with up to 7.4 million new cases occurring yearly in the United States (Source: CDC). Symptoms of trichomoniasis vary among individuals. For example, some men exhibit no symptoms at all, particularly in the early stages of the disease. As the disorder progresses, or in men with early symptoms, urethral irritation, penile discharge, and burning with urination or ejaculation can occur. Left untreated, infection can spread to other organs, such as the prostate, and can also potentially contribute to male infertility. In some women, symptoms may not appear for up to 28 days after infection, while in others symptoms arise almost immediately. Symptoms in women include painful intercourse and an unusual, strong-smelling vaginal discharge that is frothy and may be yellow-green in color. Seek prompt medical care if you are being treated for trichomoniasis but mild symptoms recur or are persistent, if you are pregnant and have trichomoniasis, if you exhibit signs of bacterial infection such as frothy urine, anorectal pain, pain or burning with urination or ejaculation, pain during sexual intercourse in women, or discharge from the penis in men and abnormal vaginal discharge in women.