Trichomoniasis is a sexually transmitted infection (STI) caused by the protozoan parasite Trichomonas vaginalis.1 It is the most prevalent nonviral STI in the United States, with 6.9 million incident trichomonas infections reported among people aged 15 to 59 years in 2018.2  If left untreated, trichomoniasis can result in preterm delivery and other adverse pregnancy outcomes and an increased risk for pelvic inflammatory disease and HIV infection.3-5 Unfortunately, many cases go undetected for months or years as trichomoniasis is often asymptomatic, with 70% to 85% of patients having minimal or no symptoms.4  

Although nitroimidazoles have been used as the standard therapy to treat trichomoniasis since the 1950s, rising rates of treatment failure due to resistant infection have prompted research into new therapies and new dosing regimens of standard therapies.4,6,7 The prevalence of resistant infection is estimated to be about 2% to 10%.5,7 Resistant cases often are difficult to differentiate from recurrent infection.4

Prevalence

The prevalence of trichomoniasis is higher in women than men aged 14 to 59 years (2.1% and 0.5%, respectively), and among Black women (9.6%) than Hispanic women (1.4%) and non-Hispanic White women (0.8%).3 Factors associated with trichomoniasis in both men and women include increasing poverty level, lower educational level, unmarried status, and having been born in the US. Among women, younger age at first sexual encounter, greater number of sex partners, and history of chlamydia infection in the past 12 months are associated with T vaginalis infection.3 Also, a higher incidence of this infection is found in correctional facilities and STI clinics.4


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Screening

Currently, no guidelines for optimal screening of asymptomatic patients for T vaginalis are available. However, the Center for Disease Control and Prevention (CDC) recommends screening for T vaginalis infection among symptomatic women with vaginal discharge as well as patients at high risk for an STI, including individuals with multiple sex partners, who exchange sex for payment, use illicit drugs, or have a history of an STI.4 The CDC recommends screening for T vaginalis in all HIV-positive women at entry into care and annually thereafter as well as at initial prenatal visits in this population.4 The American College of Obstetrician and Gynecology (ACOG) recommends screening for T vaginalis in women seeking medical care for abnormal vaginal discharge.8

Clinical Presentation

Approximately 70% of individuals with trichomoniasis are asymptomatic.1 T vaginalis infects the urethra, vagina, and endocervix of women and the urethra of men.1 Limited data is available to determine if oral and rectal tissues can store the infection.9  Symptomatic women may have diffuse, malodorous, yellow-green, vaginal discharge, which may or may not be accompanied by vulvar irritation.4,7 Other symptoms in women may include lower abdominal pain, dysuria, and dyspareunia.1,7 Symptomatic men may have urethral discharge, itching, or irritation inside the penis, dysuria, and burning after ejaculation.1 Other symptoms in men may include those associated with urethritis, epididymitis, or prostatitis.4

Diagnosis

The diagnosis of trichomoniasis for men and women is based on laboratory testing (positive nucleic acid amplification test [NAAT], motile trichomonads on wet mount, positive culture, or positive rapid antigen or nucleic acid probe test) that confirms T vaginalis.4

Nucleic Acid Amplification Tests

Nucleic acid amplification tests have become the accepted gold standard for the diagnosis of T vaginalis.10 Many NAATs have greater than 90% sensitivity and specificity.11 Specimen collection methods vary by assay but include urine collection or endocervical and vaginal swabs.

Wet Preparation Microscopy

Microscopy is most commonly used to evaluate women for trichomoniasis who present with abnormal vaginal discharge.4 It is a low-cost test and can be performed at the point of care.4 However, the sensitivity of this method ranges from 51% to 65% in vaginal specimens and is lower in urine/urethral/semen specimens in men.4 The presence of motile trichomonads on the wet mount is diagnostic of infection.

Culture

Previously, cultures were the gold standard for the detection of T vaginalis with a sensitivity ranging from 75% to 96% and specificity of up 100% in women.4 Cultures may be useful when NAATs are not available. In women, vaginal secretions are the preferred specimen type as urine culture is less sensitive.4 In men, the specimen collection method includes urine collection and urethral swab.4

Other Options for Testing

Rapid diagnostic kits (antigen or nucleic acid probe test) can be useful in high prevalence settings.4

Pharmacologic Treatment

Nitroimidazoles are the only class of antimicrobial medications known to be effective against trichomoniasis.4 Metronidazole and tinidazole are approved by the US Food and Drug Administration for oral and parenteral treatment of trichomoniasis.4

The CDC recommends a single oral dose of metronidazole or tinidazole 2 g (Figure).4 The cure rate for these single-dose regimens is 84% to 98% for metronidazole and 92% to 100% for tinidazole.4 An alternative first-line treatment recommended by the CDC is metronidazole 500 mg twice daily for 7 days.4 This 7-day regimen is recommended for patients coinfected with HIV.4

Figure. First-line treatments for T vaginalis infection. Reprinted from Workowski et al.4

ACOG recommends oral nitroimidazoles with metronidazole 500 mg twice daily x 7 days as first-line treatment due to recent clinical trials showing higher efficacy than 2 g single-dose metronidazole.8

Single-dose therapy is not always sufficient for curing T vaginalis infection.4 Treatment failure is 1.87 times more likely with a single-dose regimen of metronidazole compared with a multidose regimen, according to findings from a recent meta-analysis.12 Management of persistent infection is described below. The CDC and ACOG recommend a test of cure within 3 months for all patients.4,8 Testing with use of nucleic acid amplification can be performed as early as 2 weeks post-treatment.4

This article originally appeared on Clinical Advisor