How to Cite This Chapter: Loeb M, Ciechanowski P. Trichomoniasis. McMaster Textbook of Internal Medicine. Kraków: Medycyna Praktyczna. Accessed July 18, 2024.
Last Updated: December 13, 2021
Last Reviewed: December 13, 2021
Chapter Information


The actual incidence of trichomoniasis in North American and European Union countries is not precisely known, as this infection does not need to be reported. A single survey performed in the United States estimated a prevalence of 3.1% in women of reproductive age.Evidence 1Moderate Quality of Evidence (moderate confidence that we know true effects of the intervention). Quality of Evidence lowered due to indirectness. Sutton M, Sternberg M, Koumans EH, McQuillan G, Berman S, Markowitz L. The prevalence of Trichomonas vaginalis infection among reproductive-age women in the United States, 2001-2004. Clin Infect Dis. 2007 Nov 15;45(10):1319 -26. doi: 10.1086/522532. PMID: 17968828.

Etiology And PathogenesisTop

1. Etiologic agent: Trichomonas vaginalis is a pear-shaped, actively motile protozoan, ~10 microm long and ~7 microm wide, which replicates by binary fission and does not have a cyst form.

2. Pathogenesis: T vaginalis inhabits the lumen and surface of the genitourinary tract (lower genital tract in women and urethra and prostate in men), where it causes mucosal microulcerations.

3. Reservoir and transmission: Humans are the only hosts. T vaginalis is transmitted primarily by sexual contacts. Transmission through direct contact and contaminated objects has not been proven; the organism can survive only several hours in moist external environments. Vertical mother-to-infant transmission is rare.

4. Risk factors for infection: Multiple sexual partners, other sexually transmitted diseases.

5. Incubation and contagious period: 4 to 28 days in women.

Clinical Features And Natural HistoryTop

The disease is asymptomatic in a majority of infected women. Less than 20% have vaginitis manifested by a copious, yellowish, frothy, foul-smelling vaginal discharge, vulvar erythema and pruritus, symptoms of dysuria, urinary frequency, hypogastric pain, and dyspareunia. In some women the disease may persist for years and follow a chronic course with less severe symptoms such as pruritus, scant discharge, and dyspareunia.

In men the infection is usually asymptomatic. Some have urethritis or, less frequently, epididymitis, prostatitis, or both.


Diagnostic Tests

1. Identification of the etiologic agent:

1) Direct microscopic examination: Identification of motile T vaginalis in vaginal secretions using the hanging drop method (sensitivity, 60%-70%).

2) Molecular testing:

a) Nucleic acid amplification test (NAAT): Gold standard in the diagnostic workup of T vaginalis infection. The specimens used include vaginal swab, cervical swab, or morning urine samples in women and urethral swab samples or urine sediment in men. The sensitivity of the method is >90%, and specificity, 95% to 100%.

b) DNA hybridization test (Affirm VPIII): The sensitivity is 63%, and specificity, 99%. The result is available within 45 minutes.

3) Culture: Vaginal specimens are cultured in women, and urethral swab, urine sediment, and semen (specimens obtained from various sites and cultured on a single plate) are examined in men. Results are available within up to 7 days. The sensitivity of the test is 75% to 96%, and the specificity is ~100%.

4) Immunochromatographic antigen test: Used as a point-of-care test in the diagnostic workup in women, also as a self-administered test. Its sensitivity reaches 77% to 98%, and specificity, ~100% (data for the OSOM Trichomonas Rapid Test). The result is available within 10 minutes.

Diagnostic Criteria

Identification of T vaginalis DNA by NAAT is the gold standard in the diagnostic workup in individuals with or without clinical symptoms of infection.

Differential Diagnosis

In women: Bacterial vaginosis, vaginal candidiasis.

In women and men: Other causes of urethritis.

Patients with trichomoniasis should be tested for other sexually transmitted diseases.


Symptomatic Treatment

Oral metronidazole 500 mg every 12 hours for 7 days for women and oral metronidazole 2 g in a single dose for men. Oral tinidazole 2 g in a single dose is an alternative regimen for women and men.

Treatment should be initiated in all sexual partners of patients with trichomoniasis.


Trichomoniasis in pregnancy can cause premature rupture of membranes (PROM), premature birth, and low birth weight of the infant. Vertical transmission rarely leads to congenital infection of the genitourinary or respiratory tract in infants.

Special ConsiderationsTop

Pregnancy and Breastfeeding

As recommended by the Centers for Disease Control and Prevention (CDC) and the International Union against Sexually Transmitted Infections (IUSTI), metronidazole can be used throughout the pregnancy, while tinidazole is contraindicated in the first trimester. Women treated with metronidazole or tinidazole should stop breastfeeding for ≥3 days.


The prognosis for complete resolution of infection after completing appropriate antimicrobial therapy is good.


Specific Prevention


Nonspecific Prevention

1. Limiting the number of sexual partners and using condoms during sexual contacts.

2. Treating all sexual partners of the infected individual regardless whether they have clinical symptoms or positive results of tests for T vaginalis infection.

3. Using personal intimate hygiene products.

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