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9/1/2015

Management of Persistent and Recurrent Trichomoniasis

Trichomonas vaginalis (T. vaginalis) is a protozoan parasite and is the most common nonviral sexually transmitted infection (STI), with 3-5 million cases annually, in the United States.  Health disparities are seen with Trichomonas which is more prevalent in black women.  Risk factors also include low socioeconomic status, increased number of sex partners, and douching.

Transmission of Trichomonas occurs through sexual contact. More than 50% of women have minimal or no symptoms. Those with symptoms often complain of vulvar or vaginal irritation, malodorous yellow-green vaginal discharge, pruritis, and postcoital bleeding.

Trichomoniasis causes an elevated pH and an inflammatory green or yellow discharge that is bubbly in appearance.  The recommended diagnostic test is a nucleic acid amplification test NAAT) that is both sensitive (95%) and specific (95%) and can be performed on urine, vaginal, or cervical specimens.  The observation of unicellular, oval, motile parasites on saline microscopy (wet mount) is less sensitive at 55-60%. There are also point of care antigen-detection commercial tests that would be an alternative to NAAT (sensitivity 88%).

Oral nitroimidazoles (metronidazole and tinidazole in the U.S.) are the only approved drugs for treatment of trichomonas.  The recommended treatment is metronidazole, 500 mg twice daily for 7 days or alternatively tinidazole, 2g, once.  Topically applied therapy (e.g. metronidazole gel) is not effective. Patients who are intolerant or allergic should be referred to a specialist for desensitization as these are the only effective treatments. Expedited Partner therapy may be available in certain states and should be considered.

Most women who present with continued or recurrent vaginal symptoms are likely to have been nonadherent to the medication or reinfected by exposure to an untreated partner. Rates of reinfection are as high as 17%. When repeat exposure is suspected, repeating the basic treatment regimen should be adequate. Patients should be instructed to abstain from sex until their sex partner(s) have completed therapy and both patient and partner are asymptomatic.  Appropriate cleaning of sexual devices should also be considered as a potential source.  Because of this high rate of reinfection, repeat screening for reinfection at 3 months is recommended.  Testing for other STI’s including HIV should be offered.

Some recurrent infections may be from organisms with decreased sensitivity to nitroimidazoles. This has been identified in 2-5% of vaginal trichomoniasis cases. High-level antimicrobial resistance also rarely occurs. If decreased sensitivity or resistance is suspected, tinidazole can be used effectively if repeat treatment with metronidazole, 500 mg twice daily for 7 days fails.  If compliance is confirmed and repeat treatment is not successful, sending a culture to a reference laboratory for susceptibility testing can be considered.

In rare cases where infection persists despite extended treatment regimens, consultation and susceptibility testing is available through the CDC (telephone: 404-718-4141); website: https://www.cdc.gov/laboratory/specimen-submission/.

While there are no evidence-based guidelines to guide treatment of male partners of women with nitroimidazole treatment failure, the CDC recommends male partner evaluation and treatment with either a single dose of tinidazole 2g or metronidazole 500 mg orally twice a day for 7 days.

Further Reading:

Centers for Disease Control and Prevention. Sexually transmitted diseases treatment guidelines.  Trichomoniasis, 2021. Available at: https://www.cdc.gov/std/treatment-guidelines/trichomoniasis.htm

Vaginitis in Nonpregnant Patients: ACOG Practice Bulletin Summary, Number 215. Obstet Gynecol. 2020 Jan;135(1):243-245. doi: 10.1097/AOG.0000000000003605. PMID: 31856118.

Initial approval January 2015; Reaffirmed September 2016. Revised January 2018. Minor Revision July 2019. Revised September 2022; Minor Revision July 2024.

 

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