Trichomoniasis 

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] Trichomoniasis in women may be asymptomatic or may cause various symptoms, including a frothy yellow-green vaginal discharge and vulvar irritation. Men with trichomoniasis are frequently asymptomatic.^[2]

The high incidence of T vaginalis infection worldwide and coinfection 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]

In addition to the sexually transmitted species T vaginalis, other rarer Trichomonas species are occasionally observed in the mouth and in lung samples. These species are usually found in immunocompromised patients, most notably those with underlying lung cancer.

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]

In considering risk factors for prevalent trichomoniasis, drug use in the preceding 30 days was most associated with infection and with incident infection (new infection observed during the study). The most significant risk factor was sexual behavior in the preceding 30 days (with one or more partners). Women with one or more sexual partners in the preceding 30 days were 4 times more likely to acquire T vaginalis infection.^[6]

International

Worldwide, the annual incidence of trichomoniasis is about 170 million cases.^[7] 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 sexually transmitted viruses. T vaginalis infection increases the susceptibility to others viruses, including herpes, human papillomavirus (HPV), and HIV.^[8] Persons with trichomoniasis are twice as likely to develop HIV infection as the general population.^[9] 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 a 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.^[10] Other studies have reported a 1.9-fold risk of tubal infertility in women with trichomoniasis.^[11] 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.

Race

Evidence suggests that T vaginalis infection most likely increases HIV transmission. Thus, the observed higher prevalence of T vaginalis infection in African Americans is cause for concern. Although T vaginalis may increase the risk of HIV transmission by only a small to moderate amount, its high prevalence in the African American community makes it a cause of measurable increase in rates of HIV transmission. Therefore, control of T vaginalis may represent an important means of slowing HIV transmission, particularly among African Americans.^[12]

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. In female adolescents, trichomoniasis is more common than gonorrhea; this is particularly disconcerting since it increases the susceptibility to other viruses.^[8]