is transmitted through sexual contact (heterosexual or same-sex partners) or vertically through vaginal delivery.37,38
The incubation period is between 4 and 28 days.39
Men may present with symptoms of nongonococcal urethritis (ie, urethral discharge, irritation, or dysuria), whereas the most common symptom in women is a malodorous vaginal discharge. Women may also report dyspareunia, dysuria, lower abdominal pain, or vulvovaginal irritation.40,41
However, more than 50% of women and more than 75% of men infected with TV are asymptomatic.1,37
has been isolated from the vagina, cervix, urethra, periurethral glands, Bartholin glands, bladder, fallopian tubes, pouch of Douglas, prostate, and kidney.1,42
Common signs in women include vulvovaginal erythema, edema, frothy yellow-gray or green vaginal discharge, elevated pH (>6), and rarely a “strawberry” cervix.
does not survive long in acidic environments. In vitro, TV rapidly dies and lyses at pH less than 5.0.19
Vaginal secretions in women infected with TV often have a pH greater than 4.5, and application of 10% potassium hydroxide solution may release amines, and a sharp fishy odor is detected (commonly called the “whiff” test).
Culture is the criterion standard for diagnosis of TV, although this method requires incubation of vaginal secretions for 3 to 5 days and daily microscopic examinations. It has not been routinely adopted into clinical settings because of time constraints, but it is often used in research. Immediate microscopic evaluation of vaginal secretions, a “wet-prep,” from symptomatic patients is simple, rapid, and inexpensive. A wet-prep may reveal oval or round, flagellated trichomonads and many polymorphonuclear cells. Because trichomonads can be similar in size and shape to white blood cells, jerky or spinning motions are necessary to make a diagnosis. Variables that can result in a false-negative test include low parasite load, time interval between specimen collection and microscopic examination (>10 minutes), and clinician skill.43
As a result, almost half of the TV cases may be missed (). Of note, wet mount and culture perform best in symptomatic patients.44
Sensitivity and Specificity of Diagnostic Tests for TV in Women
There are 2 Food and Drug Administration (FDA)–approved point-of-care tests commercially available in the United States. Both have greater sensitivity compared with wet-prep in symptomatic patients. OSOM (Sekisui Diagnostics, Tokyo, Japan) TV is an inexpensive immunochromatographic dipstick test with high sensitivity and specificity. Results are available within 10 minutes. Affirm VPIII (Becton Dickinson, Franklin Lakes, NJ) is a DNA hybridization probe test, and results are available within an hour. In areas of high rates of loss to follow-up or in an emergency room setting, rapid testing may be useful.
Nucleic acid amplification tests, such as PCR or transcription-mediated amplification (TMA), are generally more sensitive than nonamplified tests. The same endocervical swab that is used for detection of gonorrhea and Chlamydia
can be used to detect TV using a recently FDA-approved TMA assay (APTIMA, GenProbe, San Diego, CA). Schwebke et al45
conducted a large, national multicenter FDA trial among 1025 women attending obstetrics/gynecology, family planning, or STD clinics to validate the NAAT performance characteristics in urine, endocervical and vaginal swabs, and ThinPrep samples. With an overall TV prevalence of nearly 12.7%, they reported superior performance of the TV NAAT (). This TMA assay has been compared with an earlier widely used research PCR assay and was found to be extremely sensitive and specific.46
In addition to the stand-alone APTIMA TMA, LabCorp offers the same TMA assay (NuSwab) as part of its vaginitis test panel and Becton Dickinson recently completed a clinical trial utilizing strand displacement amplification technology (BD ProbeTec).
In men, wet-prep is not sensitive, and there are not any antigen tests available. Trichomonas vaginalis
TMA is more sensitive than culture, and urethral swab performs better than urine or semen.1,47
Medicated tampons, mercurochrome, powdered boric acid, and bisodol, alkaline, and permanganate douches were prescribed for symptomatic relief in women without cure before the introduction of metronidazole in 1959. Metronidazole and tinidazole, which are select agents of the 5-nitroimidazole group, can cure TV. Systemic therapy is preferred over topical applications to achieve adequate drug concentrations in nonvaginal sites such as the urethra and periurethral glands. Cure rate for single 2-g dose oral metronidazole is 90% to 95%, whereas tinidazole cure rate approaches 100%.1
Tinidazole's greater cure is related to its longer half-life, higher tissue concentrations, and lower minimum lethal concentration.48
Metronidazole-resistant TV is estimated to occur in 2.5% to 5% of cases but is considered relative. Increasing the dose of metronidazole or switching to tinidazole can usually overcome the resistance.49,50
To prevent reinfection, sexual partners of infected patients should be treated. The Centers for Disease Control and Prevention recommends either regimen as first-line in male and female patients, but advises caution during pregnancy ().1
Treatment of TV in Pregnant and Nonpregnant Women
Historically, metronidazole therapy during pregnancy had been controversial. There was concern regarding teratogenicity because metronidazole readily crosses the placenta. Indeed, there are a few case reports of midline facial defects in infants born to mothers exposed to metronidazole during 6 to 7 weeks of pregnancy; however, most retrospective cohort studies do not find an association.51,52
Moreover, a meta-analysis that evaluated 32 studies, 7 of which included first-trimester exposure, did not find metro-nidazole to be teratogenic.53
In summary, the body of evidence suggests that metronidazole therapy during pregnancy, including the first trimester, does not lead to congenital malformations.
To reduce neonatal exposure, breast-feeding may be interrupted during metronidazole treatment and for 12 to 24 hours after the last dose. In mothers using tinidazole, it is recommended to interrupt breast-feeding for 3 days after the last dose.1
Overall, there remain several gaps in the literature regarding TV prevention, infection, and pathogenicity. Presumably, prevention efforts are lacking because there are insufficient data regarding reproductive harm or cost-effectiveness of screening and treatment of TV. In time, recent advancements in TV diagnostics will allow further progress of the field. However, until National STD guidelines advocate for TV screening, we present a few clinical scenarios pertinent to obstetric and gynecologic practice in which the diagnosis of TV may prove useful.