Encyclopedia / T / Trichomoniasis



Trichomoniasis is an infection caused by a one-celled protozoan called trichomonas. This is an extremely common cause of vaginal infections. Trichomoniasis is also known as trichomonas vaginitis, trichomonas vaginalis or sometimes trich (pronounced "trick").


Usually confined to the vagina, this organism also can invade the urinary tract and cause cystitis (inflammation of the bladder). Trichomonas can also be severe enough to cause an abnormal Pap smear - from which the organism also can be detected - and can recur. Although trichomonas can cause small red lesions on the cervix, it does not invade the uterus or fallopian tubes, nor does it affect fertility.


Trichomonis can be transmitted through sexual intercourse. In many instances, however, a history compatible with sexual transmission cannot be documented.


Trichomoniasis causes a yellow or greenish, frothy or bubbly discharge, sometimes with a foul odor, as well as itching, soreness and inflammation of the vulva and inside the vagina. Men harbor the organism in their urinary tract and usually have no symptoms at all.


A complete medical history and physical examination, including pelvic examination, is performed. The physician will prepare a wet smear by mixing a sample of the vaginal discharge with a drop of salt solution (normal saline) and examining it under a microscope.

Trichomonas organisms can be easily identified because they swim quite rapidly with their whip-like tails. Trichomonas can also cause small, dark red spots (petechiae) on the cervix. The vaginal secretions are likely to be more alkaline than normal, and the clinician may use a strip of pH paper to check acidity. The pH is likely to exceed 5.0.


The most effective drug for treatment of trichomonas is metronidazole. The most common brand name is Flagyl. The dosage is usually a single, 2,000 mg dose; or 500 mg twice daily every day for seven days. Usually, treating the female partner in a sexually active couple is enough. However, if infection recurs, the patient's sexual partner(s) must also be treated.

Side effects of Flagyl may include an allergic reaction; nausea and diarrhea; dryness of the mouth; a tinny, metallic taste; a depression in the white blood cell count (leukopenia); and intolerance to alcohol. Many, but not all, people who drink alcohol within 24 hours after Flagyl therapy experience nausea, vomiting, headache and flushing.

Flagyl should never be used during the first three months of pregnancy or while breast feeding, and some authorities say never in pregnancy.


Do any tests need to be done before treating the partner?

What treatment will you recommend?

Will you be prescribing any medication? What are the side effects?

If Flagyl is prescribed, are there any signs or symptoms that should be reported immediately?

What should be expected (or the partner expect) if alcohol is consumed?

All sexually active persons should consider using latex condoms to prevent STDs and HIV infection, even if they are using another form of contraception. Latex condoms used consistently and correctly are an effective means for preventing disease (and pregnancy). Talk openly with your partner about STDs, HIV, hepatitis B infection and the use of contraception.