Identifying and Treating Trichomoniasis

Trichomoniasis is a sexually transmitted infection (STI) that causes a foul-smelling vaginal discharge, painful urination, and genital itching in women, and urethral irritation and penile discharge in men. Many men and women do not have any signs and symptoms of the infection, making it difficult to control and treat. The organism that causes trichomoniasis is Trichomonas vaginalis, a protozoan parasite. This infection is more common among sexually active females. The most common antibiotic used for the eradication of T. vaginalis is metronidazole (Flagyl). To prevent recurrent infection, both sex partners should be treated. To reduce the risk of infection with the T. vagninalis parasite, use latex condoms or avoid sexual activity. If a pregnant woman has become infected, there is an increased risk for premature delivery, having a baby with low birth weight, and passing the infection to the infant during childbirth. Also, having trichomoniasis puts a person at risk for becoming infected with HIV.

Overview of Trichomoniasis

Trichomoniasis (often called "trich") is a common sexually transmitted infection (STI) that is caused by a protozoan parasite called Trichomonas vaginalis. The symptoms of this disease vary from woman to woman and man to man, and many with the parasite are unaware that they are infected and contagious. Trichomoniasis is more common among sexually active women, but it occurs in older adults and men as well.

Incidence and Prevalence

In the United States, around 3.7 million people have trichomoniasis, but only 30 percent develop any signs and symptoms of the infection. Infection is more common in women than men, with older women more likely to become infected compared to younger ones.

Causes of Trichomoniasis

The T. vaginalis organism is passed from an infected person to an uninfected person during sexual intercourse. For women, the lower genital tract is most commonly affected areas of the body, including the vagina, vulva, and urethra. In men, the most commonly affected area is the urethra, the inside of the penis. When two people have sex, the parasite is transmitted from the penis to the vagina or from the vagina to the penis. T. vaginalis can also infect the hands, mouth, and anus. The risk factors for this infection include:

  • Having multiple sex partners.
  • A history of other STIs.
  • A previous episode of trichomoniasis.

Signs and Symptoms of Trichomoniasis

Approximately 70 percent of people infected with trichomoniasis do not have any symptoms or signs of the infection. When the disease does cause signs and symptoms, they vary from mild irritation to serious inflammation. Most clinical manifestations develop within five to 23 days after contact.

Common symptoms and signs for men include:

  • Itching inside the penis.
  • Burning during or after urination.
  • Burning during or after ejaculation.
  • Irritation to the meatus (opening on the end of the penis).
  • Discharge from the penis.

Common symptoms and signs for women include:

  • Genital itching.
  • Genital burning.
  • Pain or discomfort with urination.
  • Thin vaginal discharge.
  • Unusual or foul smell to vaginal discharge.
  • Clear, white, yellow, or green discharge.

Complications of Trichomoniasis

Trichomoniasis increases the risk of getting and/or spreading other STIs. Trichonomiasis causes genital inflammation that makes a person more prone to infection of the HIV virus and other forms of bacteria. Pregnant women with this infection are more likely to have preterm delivery (baby is born too early). Also, babies born to infected mothers are more likely to be low birth weight (less than 5.5 pounds).

Diagnosis and Treatment of Trichomoniasis

Trichomoniasis is not diagnosed based on signs and symptoms alone. The doctor must check vaginal or penile discharge for the presence of the parasite, T. vaginalis. Once the diagnosis is confirmed by microscopic technology, trichomoniasis is treated with a single dose of prescription antibiotic medication, such as metronidazole or tinidazole. The pills can be taken by mouth and are safe during pregnancy. Approximately one in five people become reinfected as soon as three months after treatment. To avoid this, it is necessary that all sexual partners are also treated. Additionally, anyone treated for trichomoniasis should not engage in sexual activity until all signs and symptoms have resolved. To prevent contracting T. vaginalis, a person must avoid sexual activity or use latex condoms.


  • Centers for Disease Control and Prevention (2013. STD Facts – Trichomoniasis. Retrieved from:

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