STD Trichomonas May Be More Common Than Thought

Study Shows 8.7% of Women Test Positive for the Sexually Transmitted Disease

By Kathleen Doheny
WebMD Health News

Reviewed by Laura J. Martin, MD

July 12, 2011 -- A sexually transmitted infection known as Trichomonas vaginalis is more common than experts believe, especially in older women, according to a new study.

Most likely to be infected were women 45 and older. "Women, when they go for their yearly checkups, should ask their doctors to screen for this organism," says researcher Charlotte Gaydos, DrPH, professor of medicine and an infectious disease specialist at Johns Hopkins University School of Medicine.

She says screening should be routine for all sexually active women, whatever their age. She says cases of the disease should also be reportable to public health authorities, just like other sexually transmitted diseases (STDs) such as gonorrhea and chlamydia.

Gaydos presented the study at the International Society for STD Research meeting in Quebec City, Canada.

Another expert who reviewed the findings had some reservations: "I agree with her that we should be doing more widespread screening," says Bradley Stoner, MD, associate professor of medicine and anthropology at Washington University in St. Louis. But before recommending all women get screened, more data are needed, he says.

Gaydos reports receiving research funds from Gen-Probe, which makes a new test for trichomonas. She also received an honorarium for her lecture at the conference from the company.

Who Gets Trichomonas?

Gaydos and colleagues collected test samples from 7,593 U.S. women in 28 states. The women were ages 18 to 89.

Overall, 8.7% of the women tested positive for trichomonas. Earlier studies had found a rate of less than 4%.

The rates of trichomonas were higher than those for chlamydia and gonorrhea. Overall, 6.7% of the women tested positive for chlamydia and 1.7% for gonorrhea.

When the researchers looked at the age ranges and infection with trichomonas, they found that:

  • 13% of women in their 50s were infected
  • 11.3% of women in their 40s were infected
  • 7.9% of women in their 30s were infected
  • 8.3% of women in their 20s were infected

"It is very prevalent," Gaydos says of trichomonas.

African-Americans were most likely to be infected, she found. Overall, 20.2% of African-Americans and 5.7% of whites were infected.

As with several other STDs, the Southeast had the highest rates of infection -- 14.4% compared to 4.3% of women infected in the Northeast.

Symptoms of Trichomonas

Trichomonas vaginalis, also called trichomoniasis, is a parasite. Both men and women can be infected. In women, the vagina is most often infected. In men, the urine canal is the most common infection site.

The infection is spread sexually, either through penis-to-vagina intercourse or from vulva-to-vulva contact.

Those infected are often not aware, Gaydos tells WebMD. "Fifty percent [of women] may not have symptoms," she says. That may also apply to men, she says, but data are lacking.

Some infected men report an irritation inside the penis or slight burning with urination or during ejaculation.

Infected women may report a smelly vaginal discharge. The infection can also cause itching in the genital area and burning with urination.

Antibiotics given in a single dose are the usual treatment, Gaydos says. It is usually successful, but people can be reinfected if they have sexual contact again with an infected person.

Infection with Trichomonas vaginalis is linked with premature labor and low-birth-weight babies in pregnant women. The infection can increase susceptibility to HIV infection if a woman is exposed to that virus.

Testing for Trichomonas

Gen-Probe, a company based in San Diego, got clearance from the FDA in April for its new APTIMA test for Trichomonas vaginalis.

The new test, Gaydos says, is more accurate than other tests, such as those that examine a sample under the microscope. She says the new test is close to 100% sensitive. It is a nucleic acid amplification test. It works by replicating the nucleic acid found in the organism.

The cost of the new test is expected to be about $50 to $100 for consumers, she says, and insurance may cover it. The test can use the same test samples as those received for chlamydia or gonorrhea.

An estimated 7.4 million new cases of trichomoniasis occur each year in women and men, according to the CDC.

The new data may dispel the thinking that all STDs are most common in teens and young adults, Stoner tells WebMD.

It may also boost awareness. "It's a disease that flies under the radar," he says. "It's been perceived as [only] a nuisance by public health officials."

However, he says, it is more than a nuisance.

The new test should improve the accuracy of diagnosis, compared to older tests, says Stoner. He is vice president of the American Sexually Transmitted Diseases Association.


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SOURCES: Charlotte Gaydos, DrPH, professor of medicine, division of infectious diseases, Johns Hopkins University School of Medicine, Baltimore.International Society of STD Research, Quebec City, Canada, July 12, 2011.Bradley Stoner, MD, PhD, associate professor of medicine and anthropology, Washington University School of Medicine, St Louis. ©2011 WebMD, LLC. All Rights Reserved.