Trichomoniasis is the most common non-viral sexually transmitted infection worldwide, caused by the flagellated protozoan parasite Trichomonas vaginalis. WHO estimates 156 million new cases per year globally, surpassing chlamydia, gonorrhea, and syphilis combined.
Trichomoniasis (ICD-10: A59) is genitourinary infection caused by Trichomonas vaginalis, a 10-20 micrometer flagellated protozoan parasite with four anterior flagella, an undulating membrane, and a posterior axostyle. The parasite exists only as a trophozoite — there is no cyst form — which means it cannot survive outside a moist mucosal environment for long. In women, T. vaginalis infects the vagina, urethra, and paraurethral glands; in men, it infects the urethra, prostate, and sometimes the epididymis.
The key symptoms of Trichomoniasis are: Yellow-green frothy malodorous vaginal discharge — the classic presentation in symptomatic women, often more profuse than the discharge of bacterial vaginosis or candidiasis., Vulvar and vaginal itching, burning, and irritation, often severe enough to interfere with daily activities and sexual function., Dyspareunia (painful intercourse) and postcoital bleeding from inflamed friable mucosa., Dysuria, urinary frequency, and urgency from concurrent urethritis — sometimes mistaken for a urinary tract infection until vaginal symptoms are elicited., Vulvar erythema and edema visible on inspection; small petechial hemorrhages on the cervix produce the pathognomonic 'strawberry cervix' (colpitis macularis) in approximately 2% of cases., Symptoms may flare around menstruation due to changes in vaginal pH and immune response., Urethral discharge in men — typically scant, watery to mucopurulent, often noticed only as morning urethral 'crusting' or staining of underwear..
Modern diagnosis of trichomoniasis relies on nucleic acid amplification testing (NAAT), which has replaced wet-mount microscopy as the standard of care in the 2021 CDC STI Treatment Guidelines. Wet-mount microscopy of vaginal fluid — visualizing motile flagellated trophozoites — has sensitivity of only 51-65% in symptomatic women and lower in asymptomatic patients or men. NAAT (PCR or transcription-mediated amplification) has sensitivity over 95% and can be performed on vaginal swabs (self- or clinician-collected), endocervical swabs, urine, and in some assays urethral swabs in men. Point-of-care molecular tests (OSOM Trichomonas Rapid Test, Solana Trichomonas) provide results in 10-45 minutes with sensitivity 80-95%. Culture in modified Diamond's medium has 75-95% sensitivity but takes up to 7 days. Pap smear cytology occasionally reports T. vaginalis but has poor sensitivity and should not be used for diagnosis. The CDC recommends screening with NAAT in HIV-positive women annually, women in correctional facilities, women with symptoms or partners of infected men, and men who have sex with women in high-prevalence settings if they have symptoms. Routine screening of asymptomatic men is not recommended outside research and high-risk settings. All patients diagnosed with trichomoniasis should be tested for other STIs including chlamydia, gonorrhea, syphilis, and HIV — co-infection is common. Partner notification and treatment are essential because reinfection from untreated partners is the leading cause of apparent treatment failure. Test-of-cure (repeat NAAT 3 weeks after treatment) is not routinely required for women treated with the recommended 7-day metronidazole regimen, but retesting at 3 months catches reinfection.
Trichomoniasis has an excellent prognosis with adequate treatment. The 2021 CDC-recommended 7-day metronidazole regimen achieves parasitological cure in approximately 90% of women, an improvement over the older single-dose regimen. In men, single-dose metronidazole or tinidazole achieves cure in over 90%. Reinfection from an untreated partner is by far the most common cause of recurrence, accounting for the majority of apparent treatment failures. Nitroimidazole-resistant trichomoniasis is uncommon (estimated 4-10% in some US clinic populations) and is managed with high-dose tinidazole or specialist regimens with cure rates of 70-90%. Beyond cure, the broader prognostic story is the contribution of untreated trichomoniasis to HIV acquisition (approximately 1.5-fold increase), pregnancy outcomes (preterm rupture of membranes, preterm delivery, low birth weight), and ongoing transmission within sexual networks. Treatment reduces these risks. Long-term complications of treated trichomoniasis are uncommon — no chronic sequelae, no infertility, no permanent damage. The principal long-term burden is psychosocial: stigma, partner notification stress, and impact on relationships, all of which improve with accurate information and routine clinical handling.
Most uncomplicated trichomoniasis is managed in primary care, sexual health clinics, or gynecology. Refer to infectious disease or specialist STI clinic for persistent or recurrent infection despite documented adherence and partner treatment, for suspected nitroimidazole resistance, for management in advanced HIV with frequent recurrence, and for unusual presentations such as neonatal trichomoniasis or complicated genitourinary infection.
Find specialists →Symptoms typically resolve within 5-7 days of starting nitroimidazole therapy. Cure is microbiologically established within 3-7 days for most patients; persistent symptoms beyond 1 week warrant re-evaluation. Sexual activity can resume once both the patient and all partners have completed treatment and symptoms have resolved — typically 1-2 weeks. Retesting at 3 months catches asymptomatic reinfection.
No restriction on exercise during treatment. Sexual activity should be avoided until both partners complete treatment and are symptom-free. Cycling and prolonged friction may aggravate vulvar irritation in symptomatic women — consider modifying or temporarily reducing during the acute phase.
Look for a clinic that offers NAAT testing rather than relying on wet-mount microscopy — sensitivity differences are substantial. Sexual health clinics and STI specialty centers offer the fastest access to NAAT, point-of-care testing, expedited partner therapy, and comprehensive co-infection screening. Many sexual health clinics provide same-day diagnosis and treatment in a single visit.
Medically reviewed by AIHealz Medical Editorial Board · May 13, 2026
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