Trichomoniasis vaginalis is a motile, flagellate protozoan. It is the third most common cause of vaginitis. Every year, approximately 180 million women worldwide are diagnosed with this infection annually, accounting for 10% to 25% of all vaginal infections. Current belief is that T. vaginalis is almost exclusively acquired through sexual contact. Male sexual partners are infected in 30% to 80% of cases.
Symptomatic infection causes a characteristic frothy green malodorous discharge with a high pH (can be as high as 6.0).s Additionally, there may be soreness and irritation in and around the vulva and vagina, dysuria, dyspareunia, bleeding upon intercourse, inability to tolerate speculum insertion because of pain, or a superficial rash on the upper thighs with a scalded appearance. The cervix may have a characteristic appearance, called petechial strawberry cervix, in up to 25% of cases. Chronic asymptomatic infection can exist for decades in women; an infection also may present atypically. In men, infection is mostly asymptomatic, or there may be a thin white or yellow purulent discharge with dysuria (nongonococcal urethritis).
Trichomoniasis can be diagnosed on the basis of simple microscopy, pH evaluation, and amine tests. However, in as many as 50% of cases, microscopy yields negative findings in spite of strong evidence of T. vaginalis infection. In this case, PCR can be used to obtain a definitive diagnosis; however, it is more costly.
Risk Factors Associated with the Development of Trichomoniasis
Smoking, IUD use, and multiple sexual partners all increase the risk of contracting T. vaginalis. Statistically, black unmarried women who smoke cigarettes, use illicit drugs, less educated teenagers, and those of low socioeco-nomic groups are more likely to be colonized with this organism, as are women who have had greater than five sexual partners in the past 5 years, have a history of gonorrhea or other STDs, and who have an early age at first intercourse.
Risks Associated with Trichomoniasis Infection
Trichomoniasis is associated with and may act as a vehicle of transmission for other sexually transmitted diseases, including HIV., It is also associated with an increased risk of premature rupture of the membrane, premature birth, and low birth weight.
Conventional Treatment of Trichomoniasis Infection
CDC treatment guidelines for treatment of T. vaginalis infection is oral metronidazole, which has a cure rate of 90% to 95%. Unlike with other vaginal infections, treatment is recommended regardless of whether a woman is symptomatic. Treatment success may be increased with treatment of sexual partners. Sex is to be avoided until the patient and any sexual partners are cured. Follow-up is considered unnecessary in patients who are initially asymptomatic or who become asymptomatic after treatment is completed. Oral metronidazole is recommended for treatment of symptoms in pregnant women. Treatment during pregnancy has not been shown to reduce the risk of preterm delivery. Also, as stated, physicians and pregnant women may be hesitant to use this drug during pregnancy owing to potential risks of teratogenicity. A recent Cochrane review found no benefit from antimicrobial treatment for T. vaginalis during pregnancy, and in fact, implies possible harm from treatment on the basis that the largest trial was stopped early due to
increased risk of preterm labor with metronidazole treatment. As this is the only medication used to treat T. vaginalis, hypersensitivity and drug resistance are potential obstacles to therapy. Increasing dosage may overcome resistance, and a desensitization protocol is used in cases of hypersensitivity to the drug. Additionally, other drugs are available in Europe but have not yet been approved by the FDA for use in the United States.