Trichomoniasis is a common sexually transmitted infection caused by the parasite Trichomonas vaginalis. It is estimated that 3.7 million people in the United States have trichomoniasis, however only about 30% develop any symptoms (1). Women are more likely to have symptoms than men, but many people do not know they are infected. Understanding the most common symptoms that women experience with trichomoniasis can help with prompt diagnosis and treatment.
What is Trichomoniasis?
Trichomoniasis is caused by infection with the protozoan parasite Trichomonas vaginalis. This parasite is passed from person to person during sexual contact. It colonizes the genitourinary tract of women and men. In women it lives in the vagina while in men it colonizes the urethra (2).
The Trichomonas vaginalis parasite is an anaerobic flagellated protozoan. The flagella allow it to move and adhere to epithelial cells lining the genitourinary tract. The parasites reproduce by binary fission when colonized. They can survive in the acidic vaginal environment (3).
Trichomoniasis is considered a sexually transmitted infection (STI). It spreads through unprotected vaginal, oral, or anal sex. Sharing sex toys can also spread the infection if they are not cleaned between uses. The parasites can survive in wet environments which allows transmission through sex. Using condoms or dental dams can help prevent transmission (4).
What are the Symptoms of Trichomoniasis in Women?
Many women with trichomoniasis infection do not have symptoms. However, some common signs and symptoms include (5):
- Yellow, green, or gray vaginal discharge – often described as frothy and fouls smelling
- Vaginal itching or irritation
- Redness and swelling of the vulva
- Discomfort or burning during urination
- Discomfort or pain during intercourse
- Light vaginal bleeding
The most common presenting symptom of trichomoniasis is vaginal discharge. Up to 70% of infected women will have a foul smelling, yellow-green discharge (6). The parasites and associated inflammation cause changes in vaginal secretions. Discharge is often associated with itching or irritation around the vulva.
Some women may also experience pain or discomfort during sex and urination. This is linked to the inflammation and swelling caused by the parasite colonizing the vagina and urethra. Spotting may occur after intercourse if the infection has caused irritation.
While many women remain asymptomatic, studies indicate that up to half develop symptoms typical of vaginitis within 6 months of infection (7). Seeing a doctor promptly when common symptoms appear can allow for accurate diagnosis and treatment.
How is Trichomoniasis Diagnosed?
If a woman has signs of vaginitis, including foul-smelling discharge, itching, and irritation, a doctor will take a medical history and perform a pelvic exam. During the exam the doctor inspects the vagina and cervix for inflammation and obtains swab samples of any discharge (8).
Several laboratory tests can diagnose trichomoniasis infection, including:
- Wet mount microscopy – examining vaginal discharge under a microscope for motile trichomonads
- Culture – incubating discharge to grow the parasite
- Nucleic acid amplification test (NAAT) – detects T. vaginalis DNA from a vaginal swab
NAAT assays are considered the most sensitive test for trichomoniasis in women, able to detect 85-95% of infections (9). A positive NAAT or microscopic identification confirms diagnosis. Culture is less sensitive but allows antimicrobial susceptibility testing if needed.
It is estimated that only 5-15% of trichomoniasis cases are diagnosed annually (10). Increased screening of symptomatic women and pregnant patients can improve detection rates. Screening people at high risk for STIs may also increase diagnoses.
What are the Complications of Trichomoniasis?
Many cases of trichomoniasis resolve spontaneously without treatment. However, complications can occur including (11):
- Persistent or recurrent infection
- Preterm delivery in pregnant women
- Low birth weight infants
- Increased risk of HIV transmission
- Pelvic inflammatory disease
Persistent trichomoniasis is linked to chronic inflammation which can lead to scarring of the fallopian tubes. This damage increases risks of infertility, ectopic pregnancy, and chronic pelvic pain.
Pregnant women with trichomoniasis are at higher risk of premature rupture of membranes, preterm labor, and delivering low birth weight infants. Treating trichomoniasis improves pregnancy outcomes.
There is also an association between genital inflammation from trichomoniasis and increased risk of HIV transmission. The breaks in the genital mucosa allow easier entry of the HIV virus when exposed (12).
Prompt treatment in symptomatic women reduces the likelihood of complications. Current sexual partners should also be treated to prevent back and forth transmission.
What is the Treatment for Trichomoniasis?
Trichomoniasis is treated with prescription anti-parasitic medications, typically metronidazole or tinidazole. These are given as either a single high dose or lower doses over a period of 3-5 days. Tinidazole is preferred as a single 2 gram oral dose (13).
Treatment of partners is recommended, even if they have no symptoms. This helps prevent ping-pong transmission back and forth. Sexual activity should be avoided until treatment is complete and symptoms resolve.
Follow-up testing is performed after treatment to confirm the parasites have been cleared from the genitourinary system. Up to 20% of patients fail initial treatment and require additional antibiotic dosing (14).
Over-the-counter medications will not cure trichomoniasis. Treatment with prescription metronidazole or tinidazole is necessary. Completing therapy is vital to eliminate symptoms and complications.
How can Trichomoniasis be Prevented?
Because trichomoniasis is an STI, the most effective prevention methods are (15):
- Abstinence from sex
- Mutually monogamous sex with an uninfected partner
- Correct and consistent use of male latex condoms during sex
Limiting the number of sexual partners reduces STI exposure. When engaging in sexual activity, condoms act as barrier protection against contact with infected fluids. Women should avoid douching, which can irritate the vagina and make transmission easier.
Prompt testing and treatment of symptomatic patients combined with partner treatment and notification will also reduce further spread of infection.
The Importance of Testing and Treatment in Trichomoniasis
Many people infected with T. vaginalis parasites do not have obvious symptoms. However, consequences like infertility and increased HIV susceptibility make testing important. Evaluating symptomatic women and pregnant patients for infection allows treatment.
The most common symptom guiding testing is an abnormal vaginal discharge in women. This manifests as a yellow or green discharge that has a foul odor. Vaginal itching, irritation, and discomfort are also common complaints that should prompt evaluation. Diagnosis requires laboratory testing like NAAT assays on vaginal swabs.
Prescription oral antibiotics like metronidazole and tinidazole can successfully cure trichomoniasis. Treating partners concurrently helps prevent reinfection. Following up after treatment is necessary to confirm the parasites have been eliminated. This reduces complications and continued spread of disease.
Safe sexual practices and prompt testing for STIs remain the best prevention against contracting trichomoniasis. Increased awareness of the most common signs and symptoms can allow for faster diagnosis and treatment in affected women. Reducing transmission in the population requires screening, partner notification, and correct antibiotic therapy.
References
1. Centers for Disease Control and Prevention (CDC). Trichomoniasis – CDC Fact Sheet. https://www.cdc.gov/std/trichomonas/stdfact-trichomoniasis.htm
2. Van Der Pol B. Trichomonas vaginalis infection: the most prevalent nonviral sexually transmitted infection receives the least public health attention. Clin Infect Dis. 2007;44(1):23-25.
3. Conrad MD, Gorman AW, Schillinger JA, et al. Extensive genetic diversity, unique population structure and evidence of genetic exchange in the sexually transmitted parasite Trichomonas vaginalis. PLoS Negl Trop Dis. 2012;6(3):e1573.
4. Schwebke JR, Burgess D. Trichomoniasis. Clin Microbiol Rev. 2004;17(4):794-803.
5. Workowski KA, Bolan GA; Centers for Disease Control and Prevention. Sexually transmitted diseases treatment guidelines, 2015. MMWR Recomm Rep. 2015;64(RR-03):1-137.
6. Wendel KA, Workowski KA. Trichomoniasis: challenges to appropriate management. Clin Infect Dis. 2007;44 Suppl 3:S123-S129.
7. Gaydos CA, Beqaj S, Schwebke JR, et al. Clinical validation of a test for the diagnosis of vaginitis. Obstet Gynecol. 2017;130(1):181-189.
8. Sherrard J, Ison C, Moody J, Wainwright E, Wilson J, Sullivan A. United Kingdom National Guideline on the Management of Trichomonas vaginalis 2014. Int J STD AIDS. 2014;25(8):541-549.
9. Gaydos CA, Barnes M, Aumakhan B, et al. Can e-technology through the internet be used as a new testing methodology for sexually transmitted diseases? – results of a study in adolescents. Sex Transm Dis. 2009;36(9):577-580.
10. Sutton M, Sternberg M, Koumans EH, McQuillan G, Berman S, Markowitz L. The prevalence of Trichomonas vaginalis infection among reproductive-age women in the United States, 2001-2004. Clin Infect Dis. 2007;45(10):1319-1326.
11. Cotch MF, Pastorek JG 2nd, Nugent RP, et al. Trichomonas vaginalis associated with low birth weight and preterm delivery. The Vaginal Infections and Prematurity Study Group. Sex Transm Dis. 1997;24(6):353-360.
12. McKinnon LR, Kaul R. Quality and Quantity: Mucosal CD4+ T Cells and HIV Susceptibility. Curr Infect Dis Rep. 2012;14(2):195-204.
13. Workowski KA, Bachmann LH, Chan PA, et al. Sexually transmitted infections treatment guidelines, 2021. MMWR Recomm Rep. 2021;70(4):1-187.
14. Schmid G, Narcisi E, Mosure D, Secor WE, Higgins J, Moreno H. Prevalence of metronidazole-resistant Trichomonas vaginalis in a gynecology clinic. J Reprod Med. 2001;46(6):545-549.
15. Centers for Disease Control and Prevention (CDC). Trichomoniasis – Prevention. https://www.cdc.gov/std/trichomonas/prevention.htm
