Trichomonas vaginitis

Alternative names
Trichomoniasis; “Trich”

Trichomoniasis is a vaginal infection caused by a sexually-transmitted parasitic organism.

Causes, incidence, and risk factors

Trichomoniasis is caused by Trichomonas vaginalis, a single cell protozoan parasite with a whip-like tail that it uses to propel itself through vaginal and urethral mucus. This sexually-transmitted disease (STD) is found worldwide.

In the United States the highest incidence is in women between 16 and 35 years of age. This disease-causing protozoan cannot survive in the mouth or rectum, and therefore must be transmitted through penis-to-vagina intercourse or vulva-to-vulva contact with an infected partner.

The symptoms of the disease are quite different in men than in women.

In men, the infection is often without symptoms (asymptomatic), and clears spontaneously in a few weeks. Symptomatic men may experience a mild urethral itching or discharge, mild burning after urination or ejaculation, and, on occasion, may develop prostatitis or epididymitis from the infection.

Women develop a frothy, foul smelling, green-white or yellowish vaginal discharge. The volume of discharge may be large. Itching may occur on the labia and inner thighs and the labia may appear swollen.

Data on the incidence and prevalence of trichomoniasis is not as complete as that for gonorrhea and Syphilis. Figures suggest that it is a frequently encountered infection. More than half of all females with gonorrhea also have trichomonas. Frequently, individuals with one diagnosed STD have one or more additional sexually-transmitted infections.


  • discomfort with intercourse  
  • vaginal itching  
  • profuse, greenish-yellow, frothy or foamy, vaginal discharge with a foul or strong smell (malodorous)  
  • labial swelling or vulvar itching  
  • itching of the inner thighs


  • burning after urination or ejaculation  
  • itching of urethra  
  • slight discharge from urethra

Signs and tests
A pelvic examination reveals red blotches on the vaginal wall or cervix. It may also reveal a distinctive, inflamed “strawberry cervix.”

  • A wet prep (microscopic examination of discharge) demonstrates rapidly moving (motile) trichomonads in the vaginal secretions.  
  • A pap smear may also detect the presence of the organism.

In men, the disease can be hard to diagnose without special culture techniques, but men are treated presumptively if infection is diagnosed in female sexual partners.

Men may also be treated presumptively if they have ongoing symptoms of urethral burning and/or itching despite treatment for gonorrhea and chlamydia.

Treatment with antibiotics is used to cure the infection. Metronidazole is commonly used. It is important to avoid drinking alcohol throughout the course of treatment and for 48 hours after antibiotics are completed. Use of alcohol with metronidazole can cause severe nausea and vomiting. Avoid intercourse until treatment has been completed.

Sexual partners should be considered infected and should be treated at the same time, even if they have no symptoms.

Expectations (prognosis)
The outcome is likely to be excellent if the condition is treated adequately.


If prolonged infection is present, it may cause changes in the tissue on the cervical surface. These changes may be noted on a routine Pap smear. In such cases, treatment should be initiated and the Pap smear repeated 3 to 6 months after successful treatment.

It is important that trichomoniasis be treated to prevent symptoms and transmission to partners. Trichomoniasis can also increase the probability of acquiring HIV infection from an infected partner.

Calling your health care provider
Call for an appointment with your health care provider if any unusual vaginal discharge or irritation is noted.

Also call for an appointment if you suspect that you have been exposed to the disease.


Trichomoniasis is present in the sexually active population of all ages. A monogamous sexual relationship with a known healthy partner can help reduce the risk of this and all other sexually-transmitted diseases.

Barring total abstinence, condoms remain the best and most reliable protection against this and other sexually-transmitted diseases. Condoms must be used consistently and correctly. See safer sex behaviors.

Johns Hopkins patient information

Last revised: December 6, 2012
by Simon D. Mitin, M.D.

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