Trichomonas vaginalis is a single cell flagellum parasite that lives in the female vagina and the male urethra. It can be asymptomatic, or can cause vaginal inflammation and lead to a vaginal discharge and odor that brings a woman to the doctors office for diagnosis and treatment. Trichomoniasis is one of the easier to diagnose causes of vaginitis, as the organism is easily seen under the microscope when a drop of normal saline is used to dilute a sample of vaginal secretions obtained with a cotton swab at the time of a vaginal examination.
Trichomonas vaginalis is a single cell protozoan with flagella that it uses in a whip like fashion for self-propulsion. This organism does not have a cyst, and infections are transmitted directly when the organism moves from one host to another, usually during sexual contact. Trichomoniasis is felt to be the most common protozoan infection in people of the developed world, and the WHO estimates a worldwide 180 million cases annually, with about 5 million or more cases annually in North America.
The Trichomonas Vaginalis organism is oval shaped and slightly larger than a white blood cell when seen microscopically. It is usually easy to identify by its movement and the motion of the flagella which tend to constantly be whipping about to propel the protozoa. Each organism has 5 flagella, four that project outwards, and one that seems to stay near the surface of the organism. The purpose of this fifth flagella is not understood. Because T. vaginalis has no cyst form, it cannot survive for extended periods outside its host, but can live for up to a day or so in water, semen or urine, and can survive an hour or two on a wet surface. This said, the vast majority of infections are sexually transmitted.
Men with trichomoniasis are usually asymptomatic, although a mild urethritis may be noted. In women the typical symptoms are of vaginitis. This causes a frothy whitish yellow discharge, sometimes the cervix has a reddish appearance called a strawberry cervix, and can sometimes cause urinary symptoms if the organism is also in the urethra. Diagnosis is occasionally made when the organisms are seen in a urine specimen examined microscopically. This is most likely because of vaginal discharge contaminating the urine, though may be from urethral organisms also.
Condoms are partially effective at prevention of transmission of this organism with sexual intercourse. Treatment requires treatment of both partners in a relationship to prevent repeated infections after treatment. The usual treatment medication is metronidazole. This can be dosed as a single oral dose, or a week long course of therapy.