Trichomoniasis

This protozoal infection was previously considered a common but minor sexually transmitted disease. Lately, however, its importance has been reassessed in light of its associations with other STDs, particularly HIV, and with possible preterm birth (Soper, 2004). Trichomonas vaginalis was identified in 13 percent of nearly 14,000 women cultured at midpregnancy by the Vaginal Infections and Prematurity Study Group (Cotch and colleagues, 1991). Ethnic-specific prevalence was 23 percent for blacks and about 6 percent for Hispanic and white women.

Symptomatic vaginitis is less common and is characterized by a yellow discharge, abnormal odor, and vulvar pruritus. These women usually have a purulent vaginal discharge, vulvovaginal erythema, and colpitis macularis or strawberry cervix. Trichomonads are demonstrated readily in a wet mount of vaginal secretions as flagellated, ovoid, motile organisms that are somewhat larger than leukocytes.

The sensitivity of this technique depends on the concentration of organisms, the degree of dilution, and the experience of the examiner, but it is generally considered to be 60 to 85 percent. Trichomonads are identified most accurately by culture using Diamond medium. PCR techniques under development have had variable results (Schwebke, 2002).

The Vaginal Infections and Prematurity Study Group reported significant associations between trichomoniasis and preterm prematurely ruptured membranes, preterm delivery, and low-birthweight neonates (Cotch and associates, 1997). According to Goldenberg and co-workers (1997), however, the association with preterm delivery is difficult to assess because of commonly associated risk factors. Prenatal screening for asymptomatic infection and treatment of carriers was unexpectedly associated with an increased rate of preterm births (Klebanoff and colleagues, 2001). Similarly, Kigozi and associates (2003) also reported an increased rate of low-birthweight neonates in a cohort of women treated for trichomoniasis. It is currently recommended that only symptomatic infections be treated.

TREATMENT.
Metronidazole is the only trichomonacidal drug available in the United States, and it is quite effective. Oral administration is preferred. Lossick (1990) reviewed clinical experiences with metronidazole and found that 250 mg given three times daily for 7 days, or 2 g as a single dose, had median cure rates of 92 and 96 percent, respectively. There are few data regarding efficacy of any regimen in pregnancy. According to the Centers for Disease Control and Prevention (2002d), pregnant women can be treated with either a single 2-g oral dose, or 500 mg twice a day for 7 days. Several studies and meta-analyses have not detected association with teratogenic or mutagenic effects in fetuses.

Men have a transient infection with T vaginalis. Although the need for concomitant treatment is uncertain, most investigators have found higher relapse rates in women whose partners were not treated. Thus, the Centers for Disease Control and Prevention (2002d) recommend that all partners be treated.

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Revision date: June 20, 2011
Last revised: by Sebastian Scheller, MD, ScD