Trichomoniasis is infection of the vagina or male genital tract with Trichomonas vaginalis. It can be asymptomatic or cause urethritis, vaginitis, or occasionally cystitis, epididymitis, or prostatitis. Diagnosis is by direct microscopic examination, dipstick tests, or nucleic acid amplification tests of vaginal secretions or by urine or urethral culture. Patients and sex partners are treated with metronidazole, tinidazole, or secnidazole.. It can be asymptomatic or cause urethritis, vaginitis, or occasionally cystitis, epididymitis, or prostatitis. Diagnosis is by direct microscopic examination, dipstick tests, or nucleic acid amplification tests of vaginal secretions or by urine or urethral culture. Patients and sex partners are treated with metronidazole, tinidazole, or secnidazole.
(See also Overview of Sexually Transmitted Infections.)
Trichomonas vaginalis is a flagellated, sexually transmitted protozoan that more often infects women than men; worldwide prevalence estimates in 2016 were 5.3% among women and 0.6% among men. Over 150 million new cases occur annually (1).
Infection may be asymptomatic in either sex. In men, the organism may persist for long periods in the genitourinary tract without causing symptoms and may be transmitted to sex partners. Trichomoniasis may account for up to 8% of nongonococcal, nonchlamydial urethritis in men in some areas (2).
Coinfection with gonorrhea and other sexually transmitted infections (STIs) is common.
General references
1. Rowley J, Vander Hoorn S, Korenromp E, et al. Chlamydia, gonorrhoea, trichomoniasis and syphilis: global prevalence and incidence estimates, 2016. Bull World Health Organ. 2019;97(8):548-562P. doi:10.2471/BLT.18.228486
2. Williamson DA, Chen MY. Emerging and Reemerging Sexually Transmitted Infections. N Engl J Med. 2020;382(21):2023-2032. doi:10.1056/NEJMra1907194
Symptoms and Signs of Trichomoniasis
In women, symptoms of trichomoniasis range from none to copious, yellow-green, frothy vaginal discharge with a fishy odor, and soreness of the vulva and perineum, dyspareunia, and dysuria. Asymptomatic infection may become symptomatic at any time as the vulva and perineum become inflamed and edema develops in the labia. The vaginal walls and surface of the cervix may have punctate, red “strawberry” spots due to punctate mucosal hemorrhages. Urethritis and possibly cystitis may also occur.
Men are usually asymptomatic; however, sometimes urethritis results in a discharge that may be transient, frothy, or purulent or that causes dysuria and frequency, usually early in the morning. Often, urethritis is mild and causes only minimal urethral irritation and occasional moisture at the urethral meatus, under the foreskin, or both. Epididymitis and prostatitis are less common complications (1).
Symptoms and signs reference
1. Williamson DA, Chen MY. Emerging and Reemerging Sexually Transmitted Infections. N Engl J Med. 2020;382(21):2023-2032. doi:10.1056/NEJMra1907194
Diagnosis of Trichomoniasis
For women, vaginal testing with nucleic acid amplification tests (NAATs), wet-mount microscopic examination, rapid-antigen dipstick tests, or sometimes culture or cervical cytology
For men, NAAT or culture of urine or urethral swab or culture of semen
Trichomoniasis should be suspected in women with vaginitis, in men with urethritis, and in their sex partners. As with diagnosis of any STI, patients with suspected or confirmed trichomoniasis should be tested to exclude other common STIs such as gonorrhea and chlamydia. Suspicion for trichomoniasis is high if symptoms persist after patients have been treated for other infections such as gonorrhea and chlamydia.
Tests for women
In women, one of the following diagnostic tests of vaginal secretions may be performed:
NAAT
Vaginal pH and wet mount microscopy
Immunochromatographic flow dipstick test
Culture
NAATs are more sensitive than microscopic examination or culture for diagnosis of trichomoniasis in women.
Immunochromatographic flow dipstick tests are also available for point of care testing in women.
Microscopic examination enables clinicians to evaluate for trichomoniasis and bacterial vaginosis at the same time because they cause similar symptoms and/or may coexist. Vaginal secretions are obtained from the posterior fornix. The pH is measured. Secretions are then placed on 2 slides; they are diluted with 10% potassium hydroxide on one slide (KOH wet mount) and with 0.9% sodium chloride on the other (saline wet mount). For the whiff test, the KOH wet mount is checked for a fishy odor, which results from amines produced in bacterial vaginosis. The saline wet mount is examined microscopically as soon as possible to detect trichomonads, which can become immotile and more difficult to recognize within minutes after slide preparation. (Trichomonads are pear-shaped with flagella, often motile, and average 7 to 10 micrometers—about the size of white blood cells—but occasionally reach 25 micrometers.) Trichomoniasis is also commonly diagnosed by seeing the organism when a Papanicolaou (Pap) test is performed.at the same time because they cause similar symptoms and/or may coexist. Vaginal secretions are obtained from the posterior fornix. The pH is measured. Secretions are then placed on 2 slides; they are diluted with 10% potassium hydroxide on one slide (KOH wet mount) and with 0.9% sodium chloride on the other (saline wet mount). For the whiff test, the KOH wet mount is checked for a fishy odor, which results from amines produced in bacterial vaginosis. The saline wet mount is examined microscopically as soon as possible to detect trichomonads, which can become immotile and more difficult to recognize within minutes after slide preparation. (Trichomonads are pear-shaped with flagella, often motile, and average 7 to 10 micrometers—about the size of white blood cells—but occasionally reach 25 micrometers.) Trichomoniasis is also commonly diagnosed by seeing the organism when a Papanicolaou (Pap) test is performed.
Cervical cytology (Pap test) and urinalysis are not traditionally used to test for trichomoniasis, but infection is sometimes detected incidentally and should be treated.
Image obtained from the Public Health Image Library of the Centers for Disease Control and Prevention.
Tests for men
NAATs of urine or a urethral swab are the first choice for diagnosis in men.
Tests for both sexes
Culture can also be performed for diagnosis, but it is less sensitive than NAATs.
For women, vaginal specimens are preferred for culture. For men, urethral swab, urine sediment, or semen is preferred for culture.
Culture is most useful in the setting of persistent trichomonas infections where drug resistance to 5-nitroimidazoles is suspected. Culture and antimicrobial resistance testing for metronidazole and tinidazole is available in the United States through the Centers for Disease Control and Prevention (CDC). See also Submitting Specimens to CDC.
Treatment of Trichomoniasis
Oral metronidazole, tinidazole, or secnidazoleOral metronidazole, tinidazole, or secnidazole
Treatment of sex partners
Women with trichomoniasis should receive metronidazole 500 mg orally 2 times a day for 7 days. Men should receive metronidazole 2 g orally in a single dose. An alternative treatment for women and men is tinidazole 2 g orally in a single dose or a single dose of secnidazole granules 2 g mixed with a single serving of pudding, applesauce, or yogurt (Women with trichomoniasis should receive metronidazole 500 mg orally 2 times a day for 7 days. Men should receive metronidazole 2 g orally in a single dose. An alternative treatment for women and men is tinidazole 2 g orally in a single dose or a single dose of secnidazole granules 2 g mixed with a single serving of pudding, applesauce, or yogurt (1).
If infection persists in women and reinfection by sex partners has been excluded, women should be retreated with metronidazole 500 mg 2 times a day for 7 days or tinidazole 2 g orally once/day for 7 days.
Metronidazole may cause leukopenia, disulfiram-like reactions to alcohol, or candidal superinfections. This medication does cross the placenta but is generally safe to use in pregnancy (2). Tinidazole and secnidazole have not been established as safe during pregnancy and are not recommended.
Sex partners within the past 60 days and/or the most recent sex partner should be seen and treated for trichomoniasis with the same regimens based on sex and should be screened for other STIs. If poor adherence to follow-up by sex partners is likely, and if allowed by state and local law, treatment can be initiated in sex partners of patients with documented trichomoniasis without confirming the diagnosis in the partner (expedited partner therapy or EPT) (1). EPT may enhance partner adherence and reduce treatment failure due to reinfection. As with diagnosis of the primary patient, culture with antimicrobial resistance testing should be considered in cases of suspected drug resistance.
Treatment references
1. Muzny CA, Schwebke JR, Nyirjesy P, et al. Efficacy and Safety of Single Oral Dosing of Secnidazole for Trichomoniasis in Women: Results of a Phase 3, Randomized, Double-Blind, Placebo-Controlled, Delayed-Treatment Study. Clin Infect Dis. 2021;73(6):e1282-e1289. doi:10.1093/cid/ciab242
2. Workowski KA, Bachmann LH, Chan PA, et al. Sexually Transmitted Infections Treatment Guidelines, 2021. MMWR Recomm Rep. 2021;70(4):1-187. Published 2021 Jul 23. doi:10.15585/mmwr.rr7004a1. Erratum: Vol. 70, No. RR-4. MMWR Morb Mortal Wkly Rep. 2023;72(4):107-108. Published 2023 Jan 27. doi:10.15585/mmwr.mm7204a5
Key Points
Trichomoniasis can be asymptomatic, particularly in men, or cause vaginitis or sometimes urethritis.
In women, diagnose with nucleic acid amplification tests (NAATs), microscopic examination of vaginal secretions, dipstick tests, or culture.
In symptomatic men, diagnose with NAATs.
Treat patients and their sex partners with oral metronidazole, tinidazole, or secnidazole.Treat patients and their sex partners with oral metronidazole, tinidazole, or secnidazole.
Drugs Mentioned In This Article
