Trichomoniasis Overview

Trichomoniasis, or "trich," is a sexually transmitted infection or STD that occurs in both men and women and is caused by a parasite. In men, symptoms occur in the tube that carries urine out of the body (urethra). In women, the vagina and cervix are affected.

Infected, asymptomatic men commonly infect their partners, although women who are carriers can also be symptom free. Trichomoniasis often occurs with other STDs, such as gonorrhea and nongonococcal urethritis (chlamydia), particularly in women.

Incidence and Prevalence of Trichomoniasis

According to the Centers for Disease Control and Prevention (CDC), trichomoniasis is the most common curable STD. In the United States, about 3.7 million people are infected, but only about 30 of people with the parasite develop symptoms of trichomoniasis. Infection is more common in women than in men, and older women are more likely than younger women to be infected. Highest prevalence occurs in African Americans.

Cause of Trichomoniasis

Trichomoniasis is caused by the parasite Trichomonas vaginalis, which is transmitted principally through direct sexual contact. It also can be spread during mutual masturbation and by sharing sex toys.

Signs and Symptoms of Trichomoniasis

Symptoms generally appear 4 to 20 days after infection. Women may experience a profuse, frothy, yellow-green or gray vaginal discharge, sometimes with bleeding, an unpleasant vaginal odor, and vulvovaginal itching and discomfort. Painful and frequent urination, vulvovaginal swelling, discomfort during sexual intercourse, and abdominal pain may also occur. Cervical hemorrhaging is uncommon.

Symptoms in men are rare and include a pale white discharge from the penis and painful or difficult urination.

Trichomoniasis Complications

Untreated trichomoniasis has been linked to an increased risk for HIV infection. Infected pregnant women are at risk for premature birth, low birth weight, and infection or rupture of the placenta. Inflammation of the prostate (prostatitis) and inflammation of the bladder (cystitis) are associated with trichomoniasis in men.

Trichomoniasis Diagnosis

Culturing a sample of discharge is the most reliable method of diagnosis. A swab is passed through a man's urethra or a woman's vagina to collect a sample. It takes 10 days to obtain results.

In women, a microscopic examination of vaginal fluid, Pap smear, and urinalysis are performed. The cervix is examined for hemorrhaging.

Because trichomoniasis often occurs with other STDs, patients are screened for chlamydia, gonorrhea, syphilis, and HIV.

Treatment for Trichomoniasis

Metronidazole (Flagyl) and tinidazole (Tindamax) are used to treat trichomoniasis. These drugs usually are administered in a single dose. People taking them should avoid alcohol immediately after treatment, because a chemical reaction causing nausea and vomiting can result.

Side effect include nausea, headache, and abdominal cramping. Seizures and neurological damage have been reported in some people taking metronidazole, although these cases are rare. Pregnant women should consult a physician before taking these medications.

While symptoms in men usually resolve on their own within a few weeks, an asymptomatic man can spread infection to sex partners, so treatment is advised and routinely prescribed.

Publication Review By: Stanley J. Swierzewski, III, M.D.

Published: 09 Jun 1998

Last Modified: 08 Oct 2015