eMedicine Specialties > Infectious Diseases > Parasitic Infections

Trichomoniasis

Author: Darvin Scott Smith, MD, MSc, DTM&H,, Adjunct Assistant Professor, Department of Microbiology and Immunology, Stanford University; Chief of Infectious Diseases and Geographic Medicine, Department of Internal Medicine, Kaiser Redwood City Hospital
Coauthor(s): Natalia Ramos,, Stanford University, Keck School of Medicine of the University of Southern California
Contributor Information and Disclosures

Updated: Aug 20, 2008

Introduction

Background

Trichomoniasis is a sexually transmitted infection caused by the protozoa Trichomonas vaginalis. It is one of the most common sexually transmitted diseases in the United States.¹ Women with trichomoniasis may experience various symptoms, including a yellow-green vaginal discharge and vulvar irritation, or they may be asymptomatic. Men with trichomoniasis are frequently asymptomatic.²

The high incidence of trichomoniasis worldwide, its contribution to poor health outcomes, and its co-infection with other sexually transmitted infections make trichomoniasis a compelling public health concern. Notably, T vaginalis infection is believed to increase the risk of HIV transmission.¹ Trichomoniasis is also associated with adverse pregnancy outcomes, infertility, postoperative infections, and cervical neoplasia.³

Pathophysiology

T vaginalis is approximately the size of a white blood cell (about 10 μm in diameter), although its size may vary with physical conditions. Its flagellum allows it to move around vaginal and urethral tissues. T vaginalis directly damages the epithelium, leading to microulcerations of inhabited tissues, increasing the risk of HIV transmission.¹

Symptoms of trichomoniasis typically occur after an incubation period of 4-28 days. In women, T vaginalis is isolated from the vagina, cervix, urethra, bladder, and Bartholin and Skene glands. In men, the organism is found in the anterior urethra, external genitalia, prostate, epididymis, and semen.

Frequency

United States

Approximately 8 million new cases of trichomoniasis occur annually.⁴ The prevalence of T vaginalis infection at clinics that treat STDs varies from 15-54%.⁵ In men, trichomoniasis accounts for 10-21% of urethritis cases not attributable to gonorrheal or chlamydial infection.⁵

International

Worldwide, the annual incidence of trichomoniasis is about 170 million cases.⁶ The incidence of trichomoniasis in Europe is similar to that in the United States. In Africa, the prevalence of trichomoniasis may be much higher.

Mortality/Morbidity

T vaginalis infection is highly associated with the presence of other sexually transmitted infections, including gonorrhea, chlamydia, and HIV. Persons with trichomoniasis are twice as likely to develop HIV infection as the general population.⁷ Two explanations exist for the association between T vaginalis and HIV: (1) Disruption of the epithelial monolayer leads to increased passage of the HIV virus; (2) T vaginalis induces immune activation, specifically lymphocyte activation and replication and cytokine production, leading to increased viral replication in HIV-infected cells.
 
Pregnant women with T vaginalis infection are more likely than uninfected women to deliver preterm or to have other adverse pregnancy outcomes, including low birth weight, premature rupture of membranes, and intrauterine infection.¹ However, whether trichomoniasis causes the adverse outcome is unclear.¹ T vaginalis infection may also increase the transmission of HIV owing to disruption of the vaginal mucosa. Respiratory or genital infection in the newborn should also be considered.²

One study reported a higher risk of pelvic inflammatory disease in women with trichomoniasis.⁸ Other studies have reported a 1.9-fold risk of tubal infertility in women with trichomoniasis.⁹ Trichomoniasis may also play a role in cervical neoplasia and postoperative infections.³

In men, complications of untreated trichomoniasis include prostatitis, epididymitis, urethral stricture disease, and infertility. Infertility may result from a decreased sperm motility and viability.³

See the Clinical section for presenting symptoms and signs.

Sex

Symptomatic trichomoniasis is more common in women than in men. Trichomoniasis infection in men is less clinically apparent.

Age

Trichomoniasis is a sexually transmitted infection. As such, it is typically found in sexually active adolescents and adults.

Clinical

History

Women

Trichomoniasis symptoms in women range from none to severe pelvic inflammatory disease. Women with trichomoniasis frequently report a frothy yellowish-green vaginal discharge, abnormal vaginal odor, vulvovaginal itching and soreness, dyspareunia (pain during sexual intercourse), and dysuria (pain during urination). However, many infected women experience no symptoms.

Cervicitis due to trichomoniasis is characterized by 2 major signs—purulent discharge in the endocervical canal and easily induced endocervical bleeding.² However, it may also be asymptomatic.

T vaginalis infection is one of the top 3 causes of vaginitis.² Vaginitis is usually characterized by vaginal discharge, which may be accompanied by vulvar itching, irritation, and odor. The two other most common causes of vaginal discharge are anaerobic bacterial overgrowth of normal flora and candidiasis (infection with Candida albicans).²

Men

Trichomoniasis symptoms in men range from none to urethritis complicated by prostatitis. Nongonococcal nonchlamydial urethritis is the most common symptom reported by men with trichomoniasis. Symptoms of urethritis include discharge, dysuria, and urethral pruritus.² The discharge may be purulent to mucoid in character. Most symptomatic infections are intermittent and self-limiting. Complications of untreated trichomoniasis include prostatitis, epididymitis, urethral stricture disease, and infertility.

Physical

Women

• Purulent or homogenous vaginal discharge and vulvar or vaginal erythema are common.
• Colpitis macularis, or strawberry cervix, describes a diffuse or patchy macular erythematous lesion of the cervix. This is a specific sign for trichomoniasis but is visible in only 1-2% of cases without the aid of colposcopy. With colposcopy, colpitis macularis is detected in up to 45% of cases.
• Lower-abdominal tenderness may be present; however, this is described in fewer than 10% of patients. If this occurs, coexisting salpingitis or an intra-abdominal pathology is possible.
• Coexisting Neisseria gonorrhea infection, candidiasis, and bacterial vaginosis are common and may produce a mixed clinical picture.

Men

• The findings of trichomoniasis in men on physical examination are generally unremarkable unless the infection is complicated. It may be associated with local inflammatory states, including balanitis and balanoposthitis.
• Physical findings of epididymitis and prostatitis may also occur.

Causes

See Pathophysiology.

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