Trichomoniasis

What is trichomoniasis

Trichomoniasis is a very common sexually transmitted disease (STD) caused by a tiny protozoan parasite called Trichomonas vaginalis. Trichomoniasis is usually spreads during sex, but can also be spread by sharing wet towels or washers. Trichomoniasis mostly affects women, but men can get it too. Most people who have trichomoniasis do not have any symptoms.

Trichomoniasis is the most common curable STD (sexually transmitted disease). In the United States, an estimated 3.7 million people have the infection 1). However, only about 30% develop any symptoms of trichomoniasis. Trichomoniasis is more common in women than in men. Older women are more likely than younger women to have been infected with trichomoniasis.

Although symptoms of trichomoniasis vary, most people who have the Trichomonas vaginalis parasite cannot tell they are infected. Your doctor or sexual health clinic can test for and treat trichomoniasis.

Clinical manifestations in symptomatic pubertal or postpubertal females may include a diffuse foul-smelling (smelly fishy odor) vaginal discharge and vulvovaginal itch and irritation. Pain with urination or sexual intercourse and, less often, lower abdominal pain can occur. Vaginal discharge may be any color, but classically is yellow-green, frothy, and malodorous. The vulva and vaginal mucosa can be reddish and swollen. The cervix can be inflamed and sometimes is covered with numerous punctate cervical hemorrhages and swollen papillae, referred to as “strawberry” cervix. This finding occurs in less than 5% of infected females but is highly suggestive of trichomoniasis. Clinical manifestations in symptomatic men include urethritis (urethra inflammation) and, rarely, epididymitis or prostatitis. Reinfection is common, and resistance to treatment is rare but increasing. Rectal infections are uncommon, and oral infections have not been described.

The prevalence of Trichomonas vaginalis infection in the United States is estimated to be 2.3 million (3.1%) among women ages 14-49, based on a nationally representative sample of women who participated in National Health and Examination Survey (NHANES) 2001–2004. The following are other findings from this study 2):

  • An estimated 3.7 million women and men are infected with Trichomonas vaginalis in the United States 3)
  • Most women found to have trichomoniasis (85%) reported no symptoms.
  • Women with no history of sexual intercourse can still be affected by trichomoniasis (1.0%), as can pregnant women (3.2%), and women who have ever been pregnant (4.1%).
  • African American women had a prevalence of 13.3%, white women prevalence of 1.3%, and Mexican American women prevalence of 1.8%.
  • Prevalence of trichomoniasis increases with age and lifetime number of sexual partners among African American women.

It is not possible to diagnose trichomoniasis based on your symptoms alone. For both men and women, your doctor or sexual health care provider can examine you and get a laboratory test to diagnose trichomoniasis.

Trichomoniasis can be cured with a single dose of prescription antibiotic medication (either metronidazole or tinidazole), pills which can be taken by mouth. It is okay for pregnant women to take this medication. Some people who drink alcohol within 24 hours after taking this kind of antibiotic can have uncomfortable side effects.

People who have been treated for trichomoniasis can get it again. About 1 in 5 people get infected again within 3 months after treatment. To avoid getting reinfected, make sure that all of your sex partners get treated too, and wait to have sex again until all of your symptoms go away (about a week). Get checked again if your symptoms come back.

If your symptoms don’t go away after treatment, talk to your doctor or sexual health worker.

Without treatment, trichomoniasis can last months, or even years. Trichomoniasis can cause premature labor, low birth weight, or increase your risk of getting HIV, the virus that causes AIDS.

Trichomoniasis key facts

  • Trichomoniasis can be asymptomatic in men and women, and may persist silently for years.
  • Untreated trichomoniasis is associated with adverse pregnancy outcomes such as premature rupture of the membranes, preterm delivery, and low birthweight infants.
  • Douching may worsen vaginal discharge in patients with trichomoniasis.
  • Alcohol consumption is contraindicated with metronidazole and tinidazole.
  • Transmission Issues:
    • Trichomoniasis is almost always sexually transmitted.
    • Sex partners should be treated.
    • Patients should abstain from intercourse until they and their sex partners are cured (about 7 days).
    • Trichomoniasis has been associated with increased susceptibility to HIV acquisition and transmission.
  • Risk Reduction:
    • Individualize risk-reduction plans with each patient.
    • Prevention strategies include abstinence, mutual monogamy with an uninfected partner, use of condoms, and limiting the number of sex partners.
    • Latex condoms, when used consistently and correctly, can reduce the risk of transmission of Trichomonas vaginalis.
    • Douching should be avoided since it increases the risk for trichomoniasis.
    • Male circumcision reduces the risk of trichomoniasis.

Trichomoniasis in men

Trichomonas vaginalis may cause up to 11% to 13% of nongonococcal urethritis (NGU) in males, but urethral infection in males is frequently asymptomatic 4). Men with Trichomonas vaginalis infection may also present with prostatitis or epididymitis 5).

Trichomoniasis rarely causes symptoms in men. When men do have signs and symptoms, however, they might include:

  • Irritation inside the penis
  • Burning with urination or after ejaculation
  • Discharge from the penis

What are the complications of trichomoniasis?

Trichomoniasis can increase the risk of getting or spreading other sexually transmitted infections. For example, trichomoniasis can cause genital inflammation that makes it easier to get infected with HIV, or to pass the HIV virus on to a sex partner 6).

How does trichomoniasis affect a pregnant woman and her baby?

Pregnant women with trichomoniasis are more likely to have their babies too early (preterm delivery) 7). Also, babies born to infected mothers are more likely to have a low birth weight (less than 5.5 pounds) 8).

How do you get trichomoniasis?

The Trichomonas vaginalis parasite passes from an infected person to an uninfected person during sex. In women, the most commonly infected part of the body is the lower genital tract (vulva, vagina, cervix, or urethra). In men, the most commonly infected body part is the inside of the penis (urethra). During sex, the parasite usually spreads from a penis to a vagina, or from a vagina to a penis. Trichomoniasis can also spread from a vagina to another vagina. It is not common for the Trichomonas vaginalis parasite to infect other body parts, like the hands, mouth, or anus. It is unclear why some people with the trichomoniasis infection get symptoms while others do not. It probably depends on factors like a person’s age and overall health. Infected people without symptoms can still pass the infection on to others.

Resumption of Sexual Activity

Patients should be instructed to avoid sex until they and their sex partners have been treated, and until they no longer have any symptoms of trichomoniasis. This usually takes about 7 days.

Post-Treatment Follow-Up

All sexually active women who are diagnosed and treated for Trichomonas vaginalis infection (including pregnant women and women with HIV infection) should be retested 3 months after initial treatment to evaluate the possibility of reinfection. Retesting in men is not routinely recommended.

Trichomoniasis symptoms

About 70% of infected people with trichomoniasis do not have any signs or symptoms. When trichomoniasis does cause symptoms, they can range from mild irritation to severe inflammation. Some people with symptoms get them within 5 to 28 days after being infected. Others do not develop symptoms until much later. Symptoms can come and go.

Trichomoniasis symptoms in men

Men don’t usually get symptoms from trichomoniasis, but there may be a discharge from the penis, or pain when urinating.

Men with trichomoniasis may notice:

  • Itching or irritation inside the penis;
  • Burning after urination or ejaculation;
  • Discharge from the penis.

Trichomoniasis in women

Women with trichomoniasis may notice:

  • Itching, burning, redness or soreness of the genitals;
  • Vaginal itching or burning;
  • Pain during sex;
  • Discomfort with urination;
  • Pain low in the tummy;
  • A change in their vaginal discharge (i.e., thin discharge or increased volume) that can be clear, frothy, white, yellowish, greyish or greenish with an unusual fishy smell.

Having trichomoniasis can make it feel unpleasant to have sex. Without treatment, the infection can last for months or even years.

Figure 1. Trichomoniasis and Cervical Petechiae (“strawberry cervix”)

Trichomoniasis and Cervical Petechiae

Footnote: This photograph shows multiple petechiae on the cervix of a women with trichomoniasis. This manifestation in a woman with vaginal discharge strongly suggests a diagnosis of trichomoniasis and is often referred to as a ‘strawberry cervix’.

[Source 9)]

Trichomoniasis causes

Trichomoniasis is caused by Trichomonas vaginalis, which is a single-celled flagellated anaerobic protozoan parasite, a type of tiny parasite that travels between people during sexual intercourse. The incubation period between exposure and infection is unknown, but it’s thought to range from five to 28 days.

Trichomonas vaginalis is the only known protozoan parasite that infects the genital tract. Trichomonas vaginalis has four anterior flagella and one flagellum embedded in an undulating membrane (Figure 1) 10). The flagella are responsible for the jerky motility of this organism that is seen under a microscope. After attaching to vaginal epithelial cells, this globular, pear-shaped organism transforms into a thin, flat, ameboid shape 11). Trichomoniasis is almost always sexually transmitted; fomite transmission is extremely rare. T. vaginalis may persist for months to years in epithelial crypts and periglandular areas of the genital tract 12). Distinguishing persistent, subclinical infection from remote sexual acquisition is not always possible.

Figure 2. Trichomonas vaginalis

Trichomonas vaginalis

Footnote: Trichomonas vaginalis is a pear-shaped flagellated protozoan parasitic organism that is approximately 10 by 7 micrometers. The organism achieves a quivering motion via the anterior flagella and the undulating membrane. After attaching to vaginal epithelial cells, the organism takes on a more ameboid-like appearance.

[Source 13)]

Risk Factors for trichomoniasis

Investigators have identified multiple risk factors associated with trichomoniasis that include the following 14):

  • Older age
  • Multiple sex partners
  • Drug use (marijuana, crack cocaine, alcohol, cigarettes)
  • Unprotected sex with non-primary partner
  • Presence of STIs at baseline
  • Low socioeconomic status
  • Douching
  • Black race

Trichomoniasis prevention

The only way to avoid STDs (sexually transmitted diseases) is to not have vaginal, anal, or oral sex. The best way to avoid trichomoniasis is by using condoms every time you have sex. Safe sex also helps stop the spread of other sexually transmitted diseases (STDs).

To prevent re-infection with trichomoniasis, make sure any partner is treated too. It is best to avoid having sex for seven days after your or your partner’s treatment to lower the chance of you both getting the infection again.

If you are sexually active, you can do the following things to lower your chances of getting trichomoniasis:

  • Be in a long-term mutually monogamous relationship with a partner who has been tested and has negative STD test results;
  • Use latex condoms the right way every time you have sex. This can lower your chances of getting trichomoniasis. But the parasite can infect areas that are not covered by a condom – so condoms may not fully protect you from getting trichomoniasis.

Another approach is to talk about the potential risk of STDs before you have sex with a new partner. That way you can make informed choices about the level of risk you are comfortable taking with your sex life.

If you or someone you know has questions about trichomoniasis or any other STD, talk to a health care provider.

Trichomoniasis diagnosis

Your doctor is likely to take a sample from inside the vagina to test for trichomoniasis. Men can be checked with a urine test or a swab from the opening of the penis.

If you have trichomoniasis, your doctor may also want to test you for other sexually transmitted infections (STIs).

Trichomoniasis test

The traditional diagnostic method for trichomoniasis has been wet mount with microscopic visualization of motile Trichomonas vaginalis parasites on slide preparations from vaginal or urethral secretions. Ideally, specimens should be examined within 10 minutes to observe motile parasites, which are diagnostic. Wet mount is an inexpensive diagnostic test; however, sensitivity is estimated at 51-65%, and varies based on the individual performing the test and how promptly the slide is interpreted 15).

Culture has been considered the gold standard for diagnosis of trichomoniasis with a specificity approaching 100%, but it is not widely used and its sensitivity can be as low as 75–96% 16). Clinical specimens can be inoculated into transport systems such as Amies gel medium to maintain viability for up to 24 hours at room temperature 17). Culture systems such as InPouch TV (BioMed Diagnostics, San Jose, CA) allow for direct inoculation, culture and microscopic examination. Additionally, these systems can be used to transport specimens after inoculation. Such systems are useful when immediate transportation of specimens to the laboratory is not available. The specimen should be inoculated as soon as possible (within an hour of collection) to maintain viability of the organism.

Neither conventional nor liquid-based Papanicolau (Pap) smears are suitable for routine screening or diagnosis of Trichomonas vaginalis, because sensitivity is poor; in addition, positive predictive value is low in settings where the prevalence of infection is low 18).

The OSOM (formerly Xenostrip) Trichomonas Rapid Test (Sekisui Diagnostics, Framingham, MA) is an immunochromatographic capillary-flow enzyme immunoassay dipstick test and the only rapid antigen test commercially available in the US. It is performed on vaginal secretions with results available within 10 minutes. This point-of-care test is FDA-cleared for females and CLIA waived. Test specifications include sensitivity 82–95% and specificity 97–100% 19).

The Affirm VPIII Microbial Identification Test (Becton Dickinson, Franklin Lakes, NJ) is an FDA-cleared nucleic acid probe test for the diagnosis of three causes of female vaginitis: Trichomonas vaginalis, Gardnerella vaginalis and Candida albicans. Sensitivity for Trichomonas vaginalis is 63% and specificity 99.9% 20). This is considered a same-day test as it produces results in 45 minutes; however, it is characterized as a CLIA moderate complexity test.

Nucleic acid amplification tests (NAATs) are the most sensitive tests available for detection of Trichomonas vaginalis. The APTIMA Trichomonas vaginalis Assay (Hologic Gen-Probe, San Diego, CA) was FDA-cleared in 2011 for use with urine, endocervical and vaginal swabs, and endocervical specimens collected in the Hologic PreserveCyt solution (ThinPrep) from females only. Sensitivity is 95–100% and specificity is also 95–100% 21). The BD ProbeTec Trichomonas Vaginalis Qx Amplified DNA Assay (Becton Dickinson, Franklin Lakes, NJ) launched in Europe (EU cleared) in 2012, but is not FDA-cleared in the United States at this time.

Diagnosis of Trichomonas vaginalis in men has been challenging given the low sensitivity of microscopy and lack of FDA clearance to date for any NAATs or point-of-care tests for use with male specimens. Some laboratories have verified the performance characteristics of NAATs through a validation process for male urine specimens or penile-meatal swabs. Culture of urine, semen, and/or urethral swabs may be other diagnostic options for men.

Trichomoniasis test
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Trichomoniasis treatment

Trichomoniasis can be treated with medication (either metronidazole or tinidazole). These pills are taken by mouth. It is safe for pregnant women to take this medication. It is not recommended to drink alcohol within 24 hours after taking this medication.

People who have been treated for trichomoniasis can get it again. About 1 in 5 people get infected again within 3 months after receiving treatment. To avoid getting reinfected, make sure that all of your sex partners get treated. Also, wait 7- 10 days after you and your partner have been treated to have sex again. Get checked again if your symptoms come back.

Trichomoniasis cure

Recommended trichomoniasis treatment regimen 23)

  • Metronidazole 2 g orally in a single dose OR Tinidazole 2 g orally in a single dose

Alternative Regimen

  • Metronidazole 500 mg orally twice a day for 7 days

The nitroimidazoles are the only class of antimicrobial medications known to be effective against Trichomonas vaginalis infections. Of these drugs, metronidazole and tinidazole have been cleared by FDA for the oral or parenteral treatment of trichomoniasis 24). Tinidazole is generally more expensive, reaches higher levels in serum and the genitourinary tract, has a longer half-life than metronidazole (12.5 hours versus 7.3 hours), and has fewer gastrointestinal side effects 25). In randomized clinical trials, recommended metronidazole regimens have resulted in cure rates of approximately 84%–98% 26), and the recommended tinidazole regimen has resulted in cure rates of approximately 92%–100% 27). Randomized controlled trials comparing single 2 g doses of metronidazole and tinidazole suggest that tinidazole is equivalent or superior to metronidazole in achieving parasitologic cure and resolution of symptoms 28).

Metronidazole gel does not reach therapeutic levels in the urethra and perivaginal glands. Because it is less efficacious than oral metronidazole, it is not recommended.

Other Management Considerations

Providers should advise persons infected with Trichomonas vaginalis to abstain from sex until they and their sex partners are treated (i.e., when therapy has been completed and any symptoms have resolved). Testing for other STDs including HIV should be performed in persons infected with Trichomonas vaginalis.

Follow-up

Because of the high rate of reinfection among women treated for trichomoniasis (17% within 3 months in one study) 29), retesting for T. vaginalis is recommended for all sexually active women within 3 months following initial treatment regardless of whether they believe their sex partners were treated (see Diagnostic Considerations). Testing by nucleic acid amplification can be conducted as soon as 2 weeks after treatment 30). Data are insufficient to support retesting men.

Management of Sex Partners

Concurrent treatment of all sex partners is critical for symptomatic relief, microbiologic cure, and prevention of transmission and reinfections. Current partners should be referred for presumptive therapy to avoid reinfection. Partners should be advised to abstain from intercourse until they and their sex partners have been adequately treated and any symptoms have resolved. EPT might have a role in partner management for trichomoniasis 31) and can be used in states where permissible by law; however, no one partner management intervention has been shown to be superior in reducing reinfection rates. Though no definitive data exist to guide treatment for partners of persons with persistent or recurrent trichomoniasis in whom nonadherance and reinfection are unlikely, partners benefit from undergoing evaluation and receiving the same regimen as the patient (see Persistent or Recurrent Trichomoniasis).

Persistent or Recurrent Trichomoniasis

Persistent or recurrent infection caused by antimicrobial-resistant T. vaginalis or other causes should be distinguished from the possibility of reinfection from an untreated sex partner. Although most recurrent T. vaginalis infections are thought to result from reinfection, some infections might be attributed to antimicrobial resistance. Metronidazole resistance occurs in 4%–10% of cases of vaginal trichomoniasis (690,691), and tinidazole resistance in 1% 32). In general, T. vaginalis isolates have lower minimum lethal concentrations to tinidazole than metronidazole 33). Emerging nitroimidazole-resistant trichomoniasis is concerning, because few alternatives to standard therapy exist. Single-dose therapy should be avoided for treating recurrent trichomoniasis that is not likely a result of reinfection. If treatment failure has occurred with metronidazole 2 g single dose and reinfection is excluded, the patient (and their partner[s]) can be treated with metronidazole 500 mg orally twice daily for 7 days. If this regimen fails, clinicians should consider treatment with metronidazole or tinidazole at 2 g orally for 7 days. If several 1-week regimens have failed in a person who is unlikely to have nonadherence or reinfection, testing of the organism for metronidazole and tinidazole susceptibility is recommended 34). CDC has experience with susceptibility testing for nitroimidazole-resistant T. vaginalis and treatment management of infected persons and can provide assistance (https://www.cdc.gov/laboratory/specimen-submission/detail.html?CDCTestCode=CDC-10239). Higher dose tinidazole at 2–3g for 14 days, often in combination with intravaginal tinidazole, can be considered in cases of nitroimidazole-resistant infections; however, such cases should be managed in consultation with an expert.

Alternative regimens might be effective but have not been systematically evaluated; therefore, consultation with an infectious-disease specialist is recommended. The most anecdotal experience has been with intravaginal paromomycin in combination with high-dose tinidazole 35); clinical improvement has been reported with other alternative regimens including intravaginal boric acid 36) and nitazoxanide 37). The following topically applied agents have shown minimal success (<50%) and are not recommended: intravaginal betadine (povidone-iodine), clotrimazole, acetic acid, furazolidone, gentian violet, nonoxynol-9, and potassium permanganate 38). No other topical microbicide has been shown to be effective against trichomoniasis 39).

Special Considerations

Allergy, Intolerance, and Adverse Reactions

Metronidazole and tinidazole are both nitroimidazoles. Patients with an IgE mediated-type allergy to a nitroimidazole can be managed by metronidazole desensitization according to a published regimen 40) and in consultation with a specialist.

Pregnancy

T. vaginalis infection in pregnant women is associated with adverse pregnancy outcomes, particularly premature rupture of membranes, preterm delivery, and delivery of a low birthweight infant 41). Although metronidazole treatment produces parasitologic cure, certain trials have shown no significant difference in perinatal morbidity following metronidazole treatment. One trial suggested the possibility of increased preterm delivery in women with T. vaginalis infection who received metronidazole treatment 42), yet study limitations prevented definitive conclusions regarding the risks of treatment. More recent, larger studies have shown no positive or negative association between metronidazole use during pregnancy and adverse outcomes of pregnancy 43). If treatment is considered, the recommended regimen in pregnant women is metronidazole 2 g orally in a single dose. Symptomatic pregnant women, regardless of pregnancy stage, should be tested and considered for treatment. Treatment of T. vaginalis infection can relieve symptoms of vaginal discharge in pregnant women and reduce sexual transmission to partners. Although perinatal transmission of trichomoniasis is uncommon, treatment also might prevent respiratory or genital infection of the newborn 44). Clinicians should counsel symptomatic pregnant women with trichomoniasis regarding the potential risks for and benefits of treatment and about the importance of partner treatment and condom use in the prevention of sexual transmission.

The benefit of routine screening for T. vaginalis in asymptomatic pregnant women has not been established. However, screening at the first prenatal visit and prompt treatment, as appropriate, are recommended for pregnant women with HIV infection, because T. vaginalis infection is a risk factor for vertical transmission of HIV 45). Pregnant women with HIV who are treated for T. vaginalis infection should be retested 3 months after treatment.

Although metronidazole crosses the placenta, data suggest that it poses a low risk to pregnant women 46). No evidence of teratogenicity or mutagenic effects in infants has been found in multiple cross-sectional and cohort studies of pregnant women 47). Women can be treated with 2 g metronidazole in a single dose at any stage of pregnancy.

Metronidazole is secreted in breast milk. With maternal oral therapy, breastfed infants receive metronidazole in doses that are lower than those used to treat infections in infants, although the active metabolite adds to the total infant exposure. Plasma levels of the drug and metabolite are measurable, but remain less than maternal plasma levels. Although several reported case series found no evidence of adverse effects in infants exposed to metronidazole in breast milk, some clinicians advise deferring breastfeeding for 12–24 hours following maternal treatment with a single 2-g dose of metronidazole 48). Maternal treatment with metronidazole (400 mg three times daily for 7 days) produced a lower concentration in breast milk and was considered compatible with breastfeeding over longer periods of time 49).

Data from studies involving human subjects are limited regarding use of tinidazole in pregnancy; however, animal data suggest this drug poses moderate risk. Thus, tinidazole should be avoided in pregnant women, and breastfeeding should be deferred for 72 hours following a single 2-g dose of tinidazole (http://toxnet.nlm.nih.gov/newtoxnet/lactmed.htm).

HIV Infection

Up to 53% of women with HIV infection also are infected with T. vaginalis 50). T. vaginalis infection in these women is significantly associated with pelvic inflammatory disease 51), and treatment of trichomoniasis is associated with significant decreases in genital-tract HIV viral load and viral shedding 52). For these reasons, routine screening and prompt treatment are recommended for all women with HIV infection; screening should occur at entry to care and then at least annually thereafter. A randomized clinical trial involving women with HIV infection and T. vaginalis infection demonstrated that a single dose of metronidazole 2 g orally was less effective than 500 mg twice daily for 7 days 53). Thus, to improve cure rates, women with HIV infection who receive a diagnosis of T. vaginalis infection should be treated with metronidazole 500 mg orally twice daily for 7 days (rather than with a 2-g single dose of metronidazole). Factors that might interfere with standard single-dose treatment for trichomoniasis in these women include high rates of asymptomatic bacterial vaginosis co-infections, use of antiretroviral therapy, changes in vaginal ecology, and impaired immunity 54).

Treatment

Treatment reduces symptoms and signs of T. vaginalis infection and might reduce transmission. Likelihood of adverse outcomes in women with HIV is also reduced with T. vaginalis therapy.

Recommended Regimen for Women with HIV Infection:

  • Metronidazole 500 mg orally twice daily for 7 days

In women with HIV infection who receive a diagnosis of T. vaginalis infection, retesting is recommended within 3 months following initial treatment; NAAT is encouraged because of higher sensitivity of these tests. Data are insufficient to recommend routine screening, alternative treatment regimens of longer duration, or retesting in men.

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