Trichomoniasis is a common sexually transmitted disease (STD) that affects both women and men although symptoms are more common in women.


Trichomoniasis (or “trich”) is a very common sexually transmitted disease (STD) that is caused by infection with a protozoan parasite called Trichomonas vaginalis. Although symptoms of the disease vary, most women and men who have the parasite cannot tell they are infected.

There are approximately 7.4 million new cases each year.

A woman is most susceptible to infection just after having completed her menstrual period. Men may carry the organism unknowingly, since infection in men may cause mild or no symptoms.

Epidemiologic studies suggest trichomoniasis is 1.5 -4.0 times more common in African Americans than other racial/ethnic groups.

Causes and Symptoms

Because trichomoniasis is a sexually transmitted disease, it occurs more often in individuals who have multiple sexual partners. The protozoan is passed to an individual by contact within the body fluids of an infected sexual partner. It often occurs simultaneously with other sexually transmitted diseases, especially gonorrhea.

In women, the symptoms of trichomoniasis include an unpleasant vaginal odor, and a heavy, frothy, yellow discharge from the vagina. The genital area (vulva) is often very itchy, and there is frequently pain with urination or with sexual intercourse. The labia (lips) of the vagina, the vagina itself, and the cervix (the narrowed, lowest segment of the uterus which extends into the upper part of the vagina) will be bright red and irritated.

In men, there are usually no symptoms at all. Occasionally, a man will notice a small amount of yellowish discharge from his penis, usually first thing in the morning. There may be some mild discomfort while urinating.


Diagnosis is easily made by taking a sample of the discharge from the women’s vagina, or from the opening of the man’s penis. The sample is put on a slide and viewed under a microscope. The protozoa, which are able to move about, are easily viewed.


The usual treatment is a single large dose of metronidazole, or split doses over the course of a week. Sexual partners of an infected individual must all be treated, to prevent the infection being passed back and forth.

Having trichomoniasis once does not protect a person from getting it again. Following successful treatment, people can still be susceptible to re-infection.


Prognosis is excellent with appropriate treatment of the patient and all sexual partners. Without treatment, the infection can smolder on for a very long time, and can be passed to all sexual partners.

Vaginal trichomoniasis has been associated with adverse pregnancy outcomes.


The surest way to avoid transmission of STDs is to abstain from sexual contact, or to be in a long term mutually monogamous relationship with a partner who has been tested and is known to be uninfected.

Latex male condoms, when used consistently and correctly, can reduce the risk of transmission of trichomoniasis.




Center for Disease Control and Prevention – Trichomoniasis Fact Sheet 2011,

NIAID – STDs Trichomoniasis,