Experts are concerned one round of treatment is leaving women at risk.

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A disease called trichomoniasis is the most common curable STI. Getty Images

A new discovery could change the way doctors treat trichomoniasis, a common sexually transmitted disease.

Trichomoniasis is a parasite, and the most common curable STD or sexually transmitted infection (STI). It can cause people to be more susceptible to HIV, and cause serious birth complications, including low birth weight. It is much less common in men.

About 70 percent of people with trichomoniasis don’t have symptoms, so many people don’t know they have it. Inflammation from the infection is what can cause health problems.

For more than three decades, the treatment for trichomoniasis was a single dose of the antibiotic metronidazole or tinidazole.

But now, experts think there may be a better way to treat trichomoniasis.

Researchers out of the Tulane University School of Public Health and Tropical Medicine examined more than 600 women with HIV and trichomoniasis as part of a randomized trial.

Half the women took the conventional single dose of the antibiotic metronidazole. The other half received treatment over the course of seven days.

The women who took multiple doses of the treatment were half as likely to still have trichomoniasis after completing the course of treatment compared to women who took a single dose. The study results were published in The Lancet, Infectious Diseases.

“There about 3.7 million new cases of trichomoniasis each year in the United States,” Patricia Kissinger, PhD, an infectious disease epidemiologist and professor at Tulane University who led the research, said. “That means a lot of women have not been getting adequate treatment for many decades.”

Kissinger’s team conducted some research prior to the recent study that indicated the single dose was not sufficient to treat trichomoniasis.

After observing high rates of repeat trichomonal infections, they conducted the current study among HIV-infected women, and found that the seven-day dose was superior to the single-dose.

Kissinger also performed a meta-analysis of all the existing studies that compared the two types of dosing. The studies concluded that a single dose was equivalent to a multidose, but found that multiple doses were better.

“All indications are that single-dose is not as effective as multidose,” she said.

Kissinger hopes the Centers for Disease Control and Prevention (CDC) will change its recommendations for trichomoniasis treatment based on the results of her study. She has been asked to work with the CDC on STD prevention guidelines.

“This group will evaluate all the data and change the recommendations according to the evidence,” she told Healthline.

“We can no longer do something because it’s what we’ve always done. “We need evidence-based interventions to improve health,” Kissinger said. “I hope that this study will help to change the recommendations so that women can get the proper treatment for this common, curable STD.”

Dr. Alyssa Dweck, a gynecologist at CareMount Medical in Westchester County, New York, explained that the CDC recognizes a single or multiple-dose treatment as adequate.

But that’s based on a 2013 guideline that is due for an update, she noted.

She said the CDC recommends a repeat test to ensure the infection is cleared up as soon as two weeks after treatment, and up to three months after treatment.

She said it’s reasonable to suggest that women treated for trichomoniasis get the follow-up testing. Many prefer a one-time treatment because it can have adverse side effects, such as metallic taste in mouth, nausea, and inability to drink alcohol, Dweck said.

Kissinger hopes more women learn about trichomoniasis.

“Many women have never heard of trichomoniasis,” she said.

Trich is not a reportable disease so the CDC doesn’t do surveillance on it. But past research has indicated that trichomoniasis is in 3.1 percent of women between the ages of 14 to 49 and it is 4 times higher in African American women (13.3 percent) than in white women (1.3 percent).

“Women need to be aware of trichomonas vaginalis [trichomoniasis] as it is the most common nonviral STI in the world,” Kissinger added.

Fred Wyand, a spokesperson for the American Sexual Health Association (ASHA) and National Cervical Cancer Coalition, agreed that more women need to be aware of trichomoniasis.

“There is absolutely a disconnect in the prevalence of this infection and how people tend to view it,” Wyand told Healthline.

Each year, there are about 3.7 million new and existing cases of trichomoniasis in the United States. According to an ASHA survey, just 1 in 5 women is familiar with it. There was a general consensus that trich is the least common STI, Wyand said.

“So, there is a knowledge gap for certain, and in part, this fuels the tendency among many women to self-treat symptoms rather than seeking medical care,” he said.

Dr. H. Hunter Handsfield, a professor emeritus of medicine at the University of Washington Center for AIDS and STD, and former ASHA board member, said that a single dose has largely been known to be unreliable, so many clinics already recommend five to seven days of treatment.

“This study confirms that approach, and undoubtedly the next CDC guidelines will recommend five to seven days — probably seven days — treatment,” Handsfield said.

A study found that longer treatment for trichomoniasis may result in a better cure rate.

Trichomoniasis is a parasite, and the most common curable STD or sexually transmitted infection (STI).

The researchers found that, compared to women who took a single dose of an antibiotic, the women who took multiple doses of the treatment were half as likely to still have trichomoniasis after completing the course of treatment.