Trichomoniasis is the most common non-viral STI in the world!
70-85% of infections are asymptomatic, particularly men
- Most common symptoms (when present):
- malodorous thin discharge
- burning sensation
- urinary frequency
- lower abdominal pain
Appears to peak in 40-49yo women (in contrast to chlamydia, which peaks among 19-24yo women)
First-line treatment: metronidazole 500 mg BID x 7 days
- 7-day course is preferred to a single dose of 2000 mg because of higher cure rates
Word Nerd: The prefix “trich” comes from the Greek word for hair (trikhos), referring to the characteristic hairs that the trichomonas organism has on one end, called polar flagellates
Why doesn’t routine STI screening include testing for trichomonas?
CDC recommends routine screening for trichomonas in asymptomatic women with HIV
- Why? → Trichomonas infection induces an inflammatory response that recruits HIV-susceptible cells to the site of exposure (e.g. the vagina), thus trichomoniasis increases both transmission and acquisition of HIV among women. Furthermore, successful treatment of trichomoniasis can reduce HIV genital shedding.
CDC goes on to say that “Screening might be considered for persons receiving care in high-prevalence settings (e.g. STD clinics and correctional facilities) and for asymptomatic persons at high risk for infection (e.g. persons with multiple sex partners, exchanging sex for payment, illicit drug use, or a history of STD). However, data are lacking on whether screening and treatment for asymptomatic trichomoniasis in high prevalence settings or persons at high risk can reduce any adverse health events and health disparities or reduce community burden of infection”
- One issue here is that prevalence is variable. Site-specific data is often lacking, most likely because trichomoniasis isn’t a reportable disease
- A study of ~4,000 adults aged 18-59yo found the prevalence of trichomoniasis was around 0.5% and 1.8% among men and women, respectively
- Another study of ~59,000 women in STD clinics found 26% prevalence in symptomatic women and 6.5% in asymptomatic women
How do we test?
NAAT testing (gold standard)
- In our clinic we use the Affirm swab, which can be used at many sites: vagina, cervix, urethra, throat, and rectum. Urine testing is also possible!
- Sensitivity/specificity is generally above 95%
Wet preparation microscopy
- This is the traditional test, in which we can see motile trichomonads
- Only 40-60% sensitive, even among symptomatic women → we should never use microscopy as a screening method for asymptomatic women