Trichomoniasis is a common sexually transmitted infection (STI) caused by a tiny parasite called Trichomonas vaginalis (see box, below left).
Trichomoniasis can be difficult to diagnose because there may be no symptoms; and even when there are symptoms, they can be very similar to those of other conditions and STIs.
Women are more likely to have symptoms than men. They may have soreness and itching around the vagina and a change in vaginal discharge, while men may experience pain after urination and ejaculation (see Symptoms for more information).
How it is caught
Trichomoniasis is usually spread through unprotected sexual intercourse (without using a condom). You do not have to have lots of sexual partners to catch trichomoniasis - anyone who is sexually active can catch the infection and pass it on (see Causes for more information).
Outlook
Trichomoniasis is unlikely to go away without treatment. Most men and women are treated with an antibiotic called metronidazole, which is very effective. Trichomoniasis rarely causes complications.
