Trichomoniasis affects about 3.7 million people in the United States, and an estimated 1.8% of women.1
Although it likely is the most common nonviral sexually transmitted infection (STI) in the world, and is potentially dangerous for birth outcomes, it is largely overlooked in screening and diagnosis.1
The STI — caused by the parasite Trichomonas vaginalis — disproportionately affects African American women, who are at four times greater risk of infection. Trichomoniasis in pregnancy can lead to low birth weight babies and preterm delivery.
“Trichomonas vaginalis is very common. It’s not a reportable disease, so it’s more common than what we know,” says Patricia Kissinger, PhD, BSN, MPH, professor of epidemiology at Tulane University School of Public Health and Tropical Medicine in New Orleans. “We call it one of the neglected STIs because people haven’t cared about it very much.”
The CDC recently updated its STI treatment guidelines, recommending women with trichomoniasis receive multidose metronidazole 500 mg twice daily for seven days.1,2
Most people with the STI are asymptomatic. Screenings should at least be performed during pregnancy, Kissinger says.
“I hope the CDC will add this to screening and reporting,” she says. “The CDC has a lot of priorities right now, but if they would just say, ‘We should screen pregnant women,’ I’d be happy with that.”
T. vaginalis is an extracellular parasite that mostly infects the squamous epithelium of the genital tract, including the vagina, urethra, and endocervix. It also can infect the male urethra and prostate. Women can be infected for months or years.1
“It’s the only STI where we see a higher prevalence in older women,” Kissinger says. “Sometimes, we’d have an older woman get tested, and she says, ‘I’ve only slept with my husband for the last 30 years, so how can I have it?’” But a woman might have contracted it decades earlier and remained asymptomatic until she was much older.
Most people with trichomoniasis are asymptomatic. Those with symptoms often experience discomfort, including a frothy and malodorous discharge, itchiness, a sore vaginal cavity, and urination issues. For some women, the organism can end up in their fallopian tubes and cause pelvic inflammatory disease (PID). T. vaginalis infection can increase the risk of HIV infection because it causes inflammation, Kissinger explains.
In pregnancy, the STI can be destructive, causing preterm delivery and low birth weight. “They used to think it was an organism that was there and didn’t cause problems, but now we know it does cause problems,” Kissinger says. “We’re writing another paper that says Trichomonas vaginalis infection should be reportable, at least to screen pregnant women because of untoward pregnancy outcomes.”
Even without the CDC’s screening recommendation or its classification as a reportable disease, reproductive health providers can recommend screening for trichomoniasis for patients who are pregnant or planning to become pregnant. Women at high risk for infection also could be tested annually.
When women are tested for other STIs and recommended to start taking folic acid before a planned pregnancy, they also could be tested for T. vaginalis.
“It’s become much easier to screen for it now,” Kissinger says. A nucleic acid amplification test (NAAT) requires a urine sample or vaginal swab. When a woman is diagnosed and treated for the STI, her sexual partner also should be treated, she notes.
One challenge clinicians will face with treating T. vaginalis infection and following the new treatment guidelines is patient adherence to the seven-day regimen of twice-daily metronidazole.
“How do you get them to take a dose for seven days?” Kissinger asks. “Some people get a metallic taste in their mouths, and some get nausea with it, so it’s not perfect.”
Clinicians previously told patients not to drink alcohol while taking the medication. But now the advice is to restrict drinking to no more than one drink per day while on metronidazole, she adds.
Unlike the drug tinidazole, which also has been used to treat trichomoniasis, metronidazole is unlikely to cause birth defects. Pregnant patients can receive the same metronidazole regimen as non-pregnant patients.
“We did two randomized trials in HIV-positive and HIV-negative [non-pregnant] women, and we found you needed seven days [of treatment] to clear the infection,” Kissinger says. “Our study found that if you took a single dose, it was 1.8 times more likely a person would have a repeat infection, and there was treatment failure in both HIV-infected and uninfected people. The failure rate for a single dose of metronidazole was 16%.”
Retesting should occur three months after completing the medication regimen to ensure the infection does not recur, Kissinger adds.
REFERENCES
- Kissinger PJ, Gaydos CA, Seña AC, et al. Diagnosis and management of Trichomonas vaginalis: Summary of evidence reviewed for the 2021 Centers for Disease Control and Prevention Sexually Transmitted Infections Treatment Guidelines. Clin Infect Dis 2022;74:S152-S161.
- Centers for Disease Control and Prevention. Sexually transmitted infections treatment guidelines, 2021. July 22, 2021.
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