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Trichomonas is a common infection in reproductive aged women in the US; three to five million cases are detected annually.


Trichomonas is caused by a protozoan called trichomonas vaginalis. Trichomonas is almost always sexually transmitted. Trichomonas is known to occur with associated with other sexually transmitted diseases. The organism can be identified in 30 to 40 percent of the male sexual partners of infected women, although carriage in men is temporary and will usually go away on its own.


Women can contract the infection from other women, but men do not usually pass along the infection to other men.




Trichomonas infections in women can range from no symptoms to a severe genital infection. Women can have an infection and not even know it for long periods of time.


Typical symptoms include a pus-filled, foul-smelling, thin discharge (70 percent of cases) along with burning, itching, pain with urination, frequent urination, and pain with intercourse. After intercourse bleeding can also occur. Symptoms may be worse during menstruation.


You doctor should perform an exam to make the diagnosis and he or she may find redness of the vulva and the inner aspect of the vaginal; there may be green-yellow bubbly discharge present. Small, pin-point bleeding may be seen on the vagina and cervix (this finding is referred to as "strawberry cervix.")




Trichomonas can lead to a genital infection after a hysterectomy; it can lead to infertility, and cervical cancer. The infection can also lead make someone more at risk for contracting HIV.


Trichomonas infections can be potentially dangerous in pregnant women where infection may cause them to leak amniotic fluid and can cause preterm delivery. Treatment of pregnant women without any symptoms has not been shown to decrease these complications.


Infants born to infected mothers may contract infection during delivery. Symptoms in newborns may include fever, breathing problems, urinary tract infections, nasal drainage, and, in girls, vaginal discharge. Treatment of infants without any symptoms is not necessary since the infection will go away on its own when estrogen levels increase.




The diagnosis of Trichomonas should not be based on symptoms alone. Some lab tests can help to confirm the diagnosis.


Moving “trichomonads” can be seen under the microscopic when a small amount of vaginal discharge is examined under a microscope; this occurs in only 50 to 70 percent of cases. The organisms remain motile for 10 to 20 minutes after collection of the sample. Other lab findings include an elevated vaginal pH (>4.5) and an increase in white cells seen under the microscope.


Culturing a sample of the discharge is a reliable method of confirming the presence of Trichomonas. This test is not easily available to most doctors and takes up to seven days to obtain a result.


There is not a rapid test available to diagnosis Trichomonas in the United States.



Trichomonas is sometimes seen on Pap smears. Pap smears are inadequate for diagnosis of trichomonas and false positive results are common. Pap smear should not be used to diagnose trichomonas. Women who have evidence of Trichomonas on Papa smears should have testing done with examination of discharge under the microscope or culture.


On the other hand, if trichomonas is detected on newer, liquid-based pap tests, then the accuracy for this infection is higher and therefore starting treatment without any additional testing is reasonable.




Patients should not have intercourse until they and their partners have completed treatment and no longer have any symptoms (this generally takes about a week). After single dose treatment or treatment of patients without any symptoms, the couple should not have intercourse until both partners have waited at least seven days after taking the last antibiotic dose.


Treatment should be given to all non-pregnant women diagnosed with trichomonas, even if they do not have any symptoms.


Experts recommend treatment with a single by mouth dose of 2 grams (four 500 mg tablets) of either tinidazole or metronidazole. Cure rates are equal between the two treatments. Tinidazole seems to be better tolerated.


Similar cure rates are obtained with single and multiple dose treatments. The advantages of single-dose treatment include better compliance, a shorter period of alcohol avoidance, and possibly decreased fungal yeast infections. Antibiotic side effects (nausea, vomiting, headache, metallic taste, dizziness) appear to be related to the dose taken and occur less frequently with the lower doses of multiple doses, given over a longer period of time (eg, metronidazole 500 mg twice daily for seven days). There is no FDA approved multiple dose regimen for tinidazole at this time.


Antibiotics taken by mouth are preferred to vaginal treatment. Cure rates for vaginal therapy are =50 percent, which is significantly lower than with treatment taken by mouth.


Patients should not drink alcohol for 24 hours after taking metronidazole and 72 hours after tinidazole treatment because of the possibility of a severe reaction related to the antibiotic.


Treatment of male sexual partners is needed because optimal cure rates are achieved when women’s male sexual partners are treated at the same time. It is not necessary to confirm he diagnosis in the male partner before treatment. Antibiotic treatment of male partners is the same as in non-pregnant females, with the single dose treatment being the preferred method to ensure compliance (single oral dose of 2 grams of either tinidazole or metronidazole). Each partner should not have sexual intercourse until both partners have completed the treatment to prevent a repeat infection from occurring.


Infections in Men

Trichomonas in men usually does not have any symptoms and will often go away on its own, usually within 10 days. Symptoms such as pain with urination and penile discharge are present in <10 percent of cases. Potential complications include prostate infections, other infections of the head of the penis and testicles, and infertility. Testing for infections in men is not widely available.



Metronidazole is the most common medication used for treatment of trichomonas causing symptoms in pregnancy. Some doctors avoid using it in the first trimester because it crosses the placenta, so there is a possibility that it can cause harm to the baby. Additionally, Metronidazole has been shown to cause cancer in mice. Studies have not shown any relationship between metronidazole taken in the first trimester of pregnancy and birth defects. The CDC no longer discourages the use of metronidazole in the first trimester.


For pregnant women, some doctors prefer to use metronidazole 500 mg twice daily for five to seven days over the 2 g single dose regimen because of the lower frequency of side effects in women who already may have nausea related to pregnancy, but both treatments are acceptable.


Experts suggest not treating infections that do not cause any symptoms during pregnancy because studies have shown that it does not prevent, and may even increase, the risk of preterm delivery.


An alternative treatment of management of infections that cause symptoms is clotrimazole 1 percent cream inserted vaginally (best applied at bedtime) for seven continuous days. This often results in the symptoms going away, but the organism will remain in the genital tract. There is little information on the safety of tinidazole in pregnancy so experts do not yet recommend its use.


Treatment of sexual partners is important. Reinfection of treated partners of untreated women can be decreased by avoiding sexual intercourse and through the use of condoms.


Difficult To Treat Cases


The most common causes of persistent infections after antibiotic treatment is related to patients not taking all of their medication and/or a repeat infection. Single dose treatment improves compliance.


Experts recommend treating trichomonas, after failure of the single 2 g dose of metronidazole, with either tinidazole as a one-time 2 g dose or metronidazole as 500 mg twice daily for seven days. If either of these treatments is ineffective, tinidazole or metronidazole can be given at a dose of 2 g per day for five days.




The risk of contracting an infection can be decreased by use of condoms, limiting the number of sexual partners, and possibly by maintaining good genital hygiene.