Definition

Trichomoniasis is a sexually transmitted infection (STI) originating from the protozoan parasite Trichomonas vaginalis. This infection mainly impacts the urogenital area — specifically the vagina and urethra in women, and the urethra in men.

Description

• It primarily impacts the urogenital system: in women, it affects the vagina, urethra, and paraurethral glands, while in men, it mainly targets the urethra and occasionally the prostate gland.
• A substantial number of infected individuals show no symptoms (up to 70%). However, when symptoms do occur, they may include vaginal discharge that is often frothy and greenish, vulvar irritation, itching, painful urination (dysuria), and painful intercourse (dyspareunia).
• In men, symptoms may include discharge from the urethra, a burning sensation after urination or ejaculation, and discomfort within the penis.
• It is associated with a higher likelihood of obtaining or spreading other sexually transmitted infections (STIs), such as HIV.
• It can result in consequences like pelvic inflammatory disease (PID) and adverse pregnancy outcomes, including preterm birth and low birth weight.

Epidemiology

Incidence/Prevalence

• Incidence: each year, roughly 6–7 million new cases of trichomoniasis occur in USA, ranking it among the most prevalent non-viral sexually transmitted infections.
• Prevalence: an estimated 2.6 million people in the United States are infected at any moment, with up to 70% showing no symptoms, which leads to underdiagnosis.

Age

• This is most commonly seen in sexually active women between the ages of 25 and 49.
• The prevalence increases with age, in contrast to chlamydia, which is most common among adolescents.

Gender

• Women:
  • Significantly more prevalent, nearly five times more common than in men.
  • An anticipated prevalence of 2.8% among women aged 14 to 49.
• Men are commonly asymptomatic carriers, and regular screening is rare.

Race

• Non-Hispanic Black women have the highest trichomoniasis rates, up to ~13%, nearly 10 times higher than non-Hispanic White women.
• Lower socioeconomic status and limited healthcare access are linked to higher prevalence.

Risk factors

• General
  • Multiple sexual partners
  • Unprotected sex (lack of condom use)
  • History of other STIs
  • Engaging in transactional sex (sex for money or drugs)
  • Gender: Women are excessively affected
  • Education: Less than a high school education increases risk
  • Income: Living below the poverty level
  • Smoking: Active smokers have significantly higher odds
  • Incarceration history: Associated with 2–5× higher risk
  • Co-infection with bacterial vaginosis (BV) increases susceptibility.
• Physiological
  • Vaginal pH elevation: T. vaginalis raises vaginal pH, disturbing normal flora
  • Impaired immunity: Especially in HIV-positive individuals, altered vaginal ecology interferes with treatment
  • Older women: Higher occurrence suggests persistent asymptomatic infection

Etiology

• Trichomoniasis is an infection caused by the protozoan parasite known as Trichomonas vaginalis.
• It is an anaerobic parasite composed of a single cell that has flagella and infects the urogenital tract.
• Humans are the sole natural hosts.
• Primarily transmitted through genital contact during sexual activity.
• Vaginal intercourse is the primary method of transmission.
• Infected individuals frequently carry the parasite without showing symptoms, especially among men.
• Pathophysiology
  • Adhesion & Colonization:
    • T. vaginalis attaches to the squamous epithelial cells found in the vagina, urethra, and periurethral glands of women. In men, it generally colonizes the urethra and may also be found in the prostate.
  • Tissue Injury & Inflammation:
    • Secretions of cytotoxic agents.
    • It disrupts the epithelial barrier, leading to inflammation, small ulcers, and petechiae, such as the typical “strawberry cervix” observed during a speculum examination.
  • Immune Response:
    • Initiates a local response from neutrophils and macrophages, generating inflammatory cytokines, resulting in typical symptoms (discharge, itching, painful urination).
  • Alterations in the Vaginal Microbiome:
    • Disturb the natural vaginal flora by altering the dominance of lactobacilli.
    • Raises vaginal pH to greater than 4.5, creating an environment that facilitates the parasite's survival and growth.

History

• Investigate the sexual history, including recent unprotected vaginal intercourse, multiple or new sexual partners, and any potential partners with a known STI.
• Symptoms in Women: About 30% to 50% of cases show signs, including frothy, yellow-green vaginal discharge with a foul odor, vaginal irritation or burning, burning during urination, and possible postcoital bleeding due to mucosal sensitivity.
• Symptoms in Men: (Most men are asymptomatic) Mild urethral discharge (clear or pus-like), irritation during urination, possible burning sensation after ejaculation, and rarely, signs of prostatitis or epididymitis.
• Find out about the duration of the symptoms.

Physical findings on examination

• Classic signs on pelvic exam of a female patient:
  • Vaginal and vulvar redness (erythema)
  • Frothy, yellow-green discharge in the vaginal area.
  • Increased vaginal pH greater than 4.5.
  • Strawberry cervix refers to the presence of punctate hemorrhages on the ectocervix caused by the dilation of capillaries, seen in approximately 10% to 25% of symptomatic women. While this is considered classic, it may not always be observed.
  • Tenderness in the vaginal walls may be observed during a bimanual examination.
• Normal examination of a male:
  • There may be a mild discharge from the urethra.
  • The urethral opening might seem inflamed.
  • The prostate might feel tender in cases of prostatitis, although this is uncommon

Laboratory Tests

• Wet Mount Microscopy
  • Vaginal or urethral swab examined under a microscope
  • Limited sensitivity; may miss low parasite loads
• Nucleic Acid Amplification Tests (NAATs)
  • Highly sensitive and specific
  • Detects T. vaginalis RNA or DNA
  • Common platforms: Aptima® assay, Labcorp NAA test
  • Specimens: vaginal, endocervical, urethral swabs, or urine
• Rapid Antigen Tests
  • Detects parasite proteins (antigens)
  • Results available in <15 minutes
  • Used primarily for vaginal fluid sample

Diagnostic Tests

• Culture (Diamond’s medium, InPouch™)
  • Parasite is grown in specialized medium; historically the gold standard.
  • Diagnostic, highly sensitive but slower (2–7 days).
• PCR
  • Detects parasite DNA.
  • Diagnostic, similar sensitivity to NAAT.
• Adjunctive tests
  • Vaginal pH testing (>4.5) and clinical signs like “strawberry cervix” can support diagnosis but are not definitive alone.

Differential Diagnosis

• Bacterial Vaginosis (BV) – grayish discharge with fishy odor; clue cells on microscopy
• Candida (Yeast) infection – thick, white discharge; intense itching
• Gonorrhea – purulent discharge; often co-infects with trichomoniasis
• Chlamydia – mucopurulent discharge; often asymptomatic; NAAT required for diagnosis
• Desquamative Inflammatory Vaginitis (DIV) – yellow discharge, dyspareunia; elevated pH
• Vaginal Atrophy – postmenopausal women; irritation, and thinning of vaginal epithelium
• Foreign Body (e.g., retained tampon) – foul-smelling discharge
• Nonbacterial Prostatitis – in men, mimics trichomonas prostatitis; negative cultures
• Urethritis (non-gonococcal) – burning urination; may be caused by HSV, adenovirus
• Urinary Tract Infection (UTI) – dysuria and frequency; positive urine culture; lacks vaginal symptoms

General treatment items

• Women (including pregnant women): The recommended regimen is Metronidazole 500 mg taken orally twice daily for 7 days.
• Men should take 2 g of Metronidazole orally in a single dose.
• Alternative therapy (non-pregnant adults only): Tinidazole 2 g taken orally in a single dose; it is more costly but often better tolerated.
• Extended treatment with metronidazole or tinidazole (500 mg taken twice a day orally for 7 days or more) may be effective for recurrent infections.
• Metronidazole and tinidazole are both antibiotics belonging to the nitroimidazole class, which is the only category that is effective against T. vaginalis.

Surgical Interventions

• Trichomoniasis is an infection that is treated through medical treatment, and surgical intervention is not indicated.

Adjunctive Therapies

• Partner management involves providing the same treatment to all sexual partners from the past 60 days to prevent reinfection. Avoid sexual intercourse until treatment is completed and symptoms resolve
• Alcohol avoidance: Refrain from drinking alcohol during therapy and for 24 hours after taking metronidazole, and for 72 hours after taking tinidazole, because of potential disulfiram-like reactions.
• Symptomatic Relief: Use topical antipruritics, such as mild hydrocortisone, to alleviate itching; consider analgesics or NSAIDs for pelvic pain or dysuria.
• Behavioral counseling involves educating individuals about safe sex practices, promoting consistent condom use, and encouraging regular STI testing.
• STI screening is advised for high-risk groups, such as those with HIV, multiple sexual partners, or previous STIs.

Medications indicated with specific doses

Toxoids

• Not applicable

Immunoglobulins

• Not applicable

Vasodilators

• Not applicable

Thrombolytic agents

• Not applicable

Dietary or Activity restrictions

• Avoid alcohol during treatment and for 24 hours after metronidazole
• Avoid alcohol during treatment and for 72 hours after tinidazole
• Abstain from sexual activity until both partners complete treatment and symptoms resolve
• Avoid douching – linked to increased risk of vaginal infections, including trichomoniasis

Disposition

Admission Criteria

Trichomoniasis is usually treated on an outpatient basis; these are not typical reasons for hospital admission. However, in rare cases, patients may be admitted for the following reasons.

• Inability to tolerate oral medications (e.g., persistent vomiting)
• Severe systemic illness unrelated to routine trichomoniasis
• Patient requires hospital care for another condition

Discharge criteria

• Completion of antibiotic treatment (typically metronidazole or tinidazole)
• Symptom resolution: no vaginal/urethral discharge, irritation, or dysuria
• No signs of complications
• Abstinence from sex until both the patient and partner complete therapy
• Retesting recommended at 3 months post-treatment (especially for women)
• Education on STI prevention, condom use, and risk control.

Monitoring

• Women with HIV (annual screening)
• Symptomatic individuals (vaginal discharge, dysuria, genital irritation)
• Individuals with a current STI diagnosis or multiple sexual partners
• Retesting recommended 3 months after treatment due to high reinfection rates (~20%)
• Partner notification and treatment are necessary to prevent reinfection.

Patient Education

• Goals: Enhance awareness of trichomoniasis, including how it spreads and ways to prevent it.
• Promote consistent treatment compliance and partner therapy to reduce the risk of reinfection.
• Encourage open dialogue about sexual health within families and among partners.
• General education: Work to reduce stigma, encourage testing, and safeguard reproductive health.
• Discuss the diagnosis openly and calmly, reassuring the patient that trichomoniasis is treatable.
• Action Plan for Patients and Families:
  • Take your medication precisely as prescribed.
  • Caregivers can help by providing reminders, ensuring hydration, and monitoring for side effects.
  • Return for retesting three months after treatment, as recommended by the CDC.

Complications

• Reproductive & Genitourinary Complications
  • Cervical tissue changes may result in abnormal Pap smear findings, requiring follow-up.
  • Prostatitis & Epididymitis – In men, inflammation of the prostate or epididymis can cause pain and urinary issues.
  • Vaginitis & Cervicitis – swelling of vaginal and cervical tissues, often with discharge and discomfort.
• Pregnancy-Related Risks
  • Preterm delivery – likelihood of birth before 37 weeks
  • Low birth weight – infants may weigh less than 5.5 lbs
  • Premature rupture of membranes (PROM) is linked to intrauterine infection and negative pregnancy outcomes.
  • Congenital trichomoniasis – rare vertical transmission during childbirth
• STI Amplification & HIV Susceptibility
  • Increased HIV risk – genital inflammation facilitates viral entry and transmission
  • Higher co-infection rates with gonorrhea and HPV in high-risk populations.

Prevention

To prevent trichomoniasis, it is essential to minimize sexual transmission, identify asymptomatic carriers, and manage partners effectively.

• Primary Prevention:
  • Routine use of male latex condoms, when applied consistently and adequately, decreases the likelihood of transmission.
  • Course on Sexual Health Education: Encourage safe sex habits, such as reducing the number of sexual partners and getting regular STI screenings.
  • Promote open discussions between sexual partners regarding STIs and any recent exposures.
  • Routine Screening of High-Risk Group: The CDC advises that all HIV-positive women should be screened at least once a year, with more frequent screenings for those who have multiple partners or exhibit symptoms.
  • Screening might also be taken into account for: Imprisoned individuals. Women who are sexually active and receive care at STI clinics or have a history of sexually transmitted infections.
  • Expedited Partner Therapy (EPT): Permitted in several U.S. states. It includes dispensing prescriptions or medications for the partner of a diagnosed patient without needing an independent medical assessment.
  • Avoiding Douching: Douching can interfere with the natural vaginal flora and may lead to a higher risk of sexually transmitted infections, such as T. vaginalis.
• Secondary Prevention (After Diagnosis)
  • Abstain from sex until both patient and partner have completed their medication and are symptom-free (~7 days).
  • Replicate testing in 3 months (particularly in women) to catch reinfection.

Prognosis

• Excellent with treatment: Most cases resolve completely with oral antibiotics
• Symptom resolution: Normally within 7 days of completing therapy
• Curable STI: Trichomoniasis is the most common curable non-viral STI
• High reinfection rate: ~1 in 5 individuals are reinfected within 3 months
• Partner treatment is essential: Reinfection often occurs if sexual partners are untreated
• Retesting recommended: Especially for women, at 3 months post-treatment.

Associated conditions

• Cervicitis – inflammation of the cervix, co-occurring with trichomoniasis infection
• Urethritis – especially in men, a burning sensation during urination or ejaculation
• Rare prostatitis – Trichomonas can infect the prostate gland
• Vaginitis – swelling of the vaginal mucosa, often with frothy discharge.

Synonyms

• Trich
• Trichomonas vaginalis infection

ICD-10-CM

• A59.0: Urogenital trichomoniasis
• A59.00: Urogenital trichomoniasis, unspecified
• A59.01: Trichomonal vulvovaginitis
• A59.02: Trichomonal prostatitis
• A59.03: Trichomonas cystitis and urethritis
• A59.09: Other urogenital trichomoniasis
• A59.8: Trichomoniasis of other sites
• A59.9: Trichomoniasis, unspecified

• Sherrard, J., Ison, C., Moody, J., Wainwright, E., Wilson, J., & Sullivan, A. (2014). United Kingdom National Guideline on the Management of Trichomonas vaginalis 2014. International Journal of STD & AIDS, 25(8), 541–549.
• Soper, D. E. (2004). Trichomoniasis: Under control or undercontrolled? American Journal of Obstetrics and Gynecology, 190(1), 281–290.
• Workowski, K. A., & Bolan, G. A. (2015). Sexually transmitted diseases treatment guidelines, 2015. MMWR Recommendations and Reports, 64(3), 1–137.
• Anjaeyulu, R., & Gupte, S. A. (1977). Single-dose treatment of trichomonal vaginitis: A comparison of tinidazole and metronidazole. Journal of International Medical Research, 5(6), 438–441.
• World Health Organization. (2021). Trichomoniasis – Key facts.
• Centers for Disease Control and Prevention. (2021). Trichomoniasis – STD treatment guidelines. U.S. Department of Health & Human Services.
• Mayo Clinic. (n.d.). Trichomoniasis: Diagnosis & treatment. Mayo Foundation for Medical Education and Research.