Trichomoniasis is a sexually transmitted disease (STD) caused by a tiny parasite. Also known as “trich” or “trick,” it infects both sexes but is more common in women. It is the most common nonviral STD.

Women can develop trichomoniasis after sexual contact with infected men or women – e.g., through penis-to-vagina or vulva-to-vulva contact. Infection can also be spread through oral or possibly anal sex, or exposure to certain objects that contain the parasite. These objects include:

• Damp towels and washcloths
• Wet clothing, such as bathing suits
• Toilet seats

Infection is most commonly transmitted during vaginal intercourse. Men are usually infected after sexual contact with an infected woman.

Trichomoniasis does not usually pose a serious health threat. Men rarely experience symptoms, and this is also true of many women. However, some women experience symptoms, including inflammation, irritation and itching in the genital area (vaginitis). Women also may experience yellow, green or gray vaginal discharge and discomfort during sexual intercourse (dyspareunia).

A small percentage of men may experience symptoms such as urethritis (inflammation of the urethra), itching of the urethra, dysuria (difficulty or pain during urination), a slight discharge from the penis, or slight burning following urination or ejaculation.

In diagnosing trichomoniasis, female patients will undergo a pelvic examination, during which the physician will open the walls of the vagina and look for small red sores inside the vagina or on the cervix. A sample of vaginal fluid will be obtained and examined under a microscope to determine the presence of parasites. Trichomoniasis is often more difficult to diagnose in male patients. Special culture techniques may be necessary to make a definitive diagnosis.

In most cases, trichomoniasis is treated with a single oral dose of the prescription drug metronidazole, which is used to treat bacterial, fungal and parasitic infections. The partners of people who are infected are also treated under the assumption that they, too, are infected with trichomoniasis.