Trichomoniasis: Symptoms and Treatment
Clinical Manifestations
Most infections with Trichomonas vaginalis are asymptomatic in both sexes, with approximately 80% of males and a substantial proportion of females having no symptoms. 1
Symptomatic Females
- Diffuse, malodorous, yellow-green vaginal discharge with vulvar irritation 1
- Vaginitis and cervicitis 1, 2
- Vulvar burning, dyspareunia, and external dysuria 2, 3
- Associated complications include pelvic inflammatory disease (PID), preterm labor, premature rupture of membranes, preterm delivery, and low birth weight 1, 4
- Increased risk of HIV transmission and acquisition 1, 5
Symptomatic Males
- Nongonococcal urethritis 1, 6
- Epididymitis and prostatitis (less common) 1
- Most male infections remain asymptomatic and unreported 7
Epidemiologic Considerations
- Substantial racial disparities exist, with prevalence rates 10 times higher among non-Hispanic African American females compared to non-Hispanic white and Mexican American counterparts 1
- Black males have infection rates of 3.6%, significantly higher than other racial groups 7
- Adolescent female prevalence ranges from 2.1% to 14.4% 1
Diagnostic Approach
Nucleic acid amplification tests (NAATs) are now the gold standard for diagnosis, replacing traditional wet mount microscopy which has poor sensitivity of only 60-70%. 1, 5, 6
Available Diagnostic Methods (in order of preference)
- NAAT (APTIMA): Licensed for female cervical/vaginal swabs, urine, and PreservCyt specimens; superior sensitivity in males but not FDA-licensed for male specimens 1, 5
- Point-of-care antigen detection (OSOM): CLIA-waived test with better sensitivity than wet mount 1
- Nucleic acid probe test (Affirm VPIII): Detects T. vaginalis, Gardnerella vaginalis, and Candida albicans 1
- Culture in Diamond media or InPouch system: Greater sensitivity than wet mount 1
- Wet mount microscopy: Requires immediate viewing, poor sensitivity (60-70%), high false-negative rate 1, 3
Critical Diagnostic Pitfalls
- Papanicolaou test should NOT be used to diagnose T. vaginalis due to poor sensitivity and specificity 1
- Wet mount false-negatives commonly lead to underrecognition and undertreatment 1
Treatment Regimens
First-Line Treatment for Females
Metronidazole 500 mg orally twice daily for 7 days is the preferred regimen, with cure rates of approximately 90-95%. 4, 5
- Alternative: Metronidazole 2g orally as a single dose 8, 9, 10
- The 7-day regimen is superior to single-dose therapy, reducing treatment failure at 1-month follow-up 5
First-Line Treatment for Males
Metronidazole 2g orally in a single dose remains the preferred treatment for males, with cure rates of approximately 90-95%. 8, 9, 5
- Alternative: Metronidazole 500mg orally twice daily for 7 days when adherence is assured 8
Alternative Agent
Critical Management Requirements
Partner Treatment (Mandatory)
All sexual partners must be treated simultaneously to prevent reinfection, which is the most common cause of treatment failure. 1, 8, 4, 9, 10
- Patients must abstain from sexual activity until both they and all partners complete treatment and are asymptomatic 8, 4, 9
- Asymptomatic male partners should be treated even with negative cultures, as the organism is difficult to isolate from males 10
Follow-Up and Rescreening
- Routine follow-up is unnecessary for patients who become asymptomatic after treatment 1, 8, 4
- Rescreening at 3 months after treatment is recommended for females, especially HIV-infected females, due to high rates of reinfection 1, 5
- If symptoms persist after treatment, consider reinfection or resistant infection 8
Treatment Failure Protocol
Stepwise Approach
- First failure: Re-treat with metronidazole 500mg twice daily for 7 days 8, 4, 9
- Second failure: Metronidazole 2g once daily for 3-5 days 8, 4, 9
- Persistent failure: Consult infectious disease specialist and consider susceptibility testing after excluding reinfection 8, 4, 9
Resistance Considerations
- In vitro antibiotic resistance to 5-nitroimidazole remains low at 4.3% but requires monitoring 5
- Metronidazole resistance is an emerging problem, though clinical importance is not yet fully clear 2
Special Populations
Pregnancy
- Metronidazole is contraindicated during the first trimester of pregnancy 4
- After the first trimester: Metronidazole 2g orally in a single dose 4
- Treatment is important due to associations with premature rupture of membranes, preterm delivery, and low birth weight 1, 4
- Follow-up evaluation one month after treatment completion is required to verify therapeutic effectiveness 1
HIV-Infected Patients
Patients with HIV infection should receive the same treatment regimens as HIV-negative individuals. 1, 8, 4, 9
- Annual screening for T. vaginalis is recommended in HIV-infected females 1
Breastfeeding
- The 7-day regimen may be preferred if the patient cannot interrupt breastfeeding, as lower daily doses result in less drug accumulation in breast milk 9
Metronidazole Allergy
- For true metronidazole allergy, desensitization may be required as effective alternatives are limited 8, 4, 9
- Nitroimidazoles are the only effective oral class for trichomoniasis 9
Common Pitfalls to Avoid
Critical Errors
- NEVER use topical metronidazole gel for trichomoniasis—efficacy is <50% and it should not be used 8, 9
- Failing to treat sexual partners simultaneously leads to reinfection 8, 9
- Using Papanicolaou test for diagnosis due to poor sensitivity and specificity 1
- Relying on wet mount microscopy alone, which misses 30-40% of infections 1