The causative organism of trichomoniasis is a flagellated protozoan, T. vaginalis, that may live quiescently in paraurethral Skene’s glands and from this nidus of infestation cause overt infection in the susceptible vagina. Trichomonads are frequently found in the urethra and may be recovered from urine. It is estimated that 2 to 3 million American women contract the disease annually. Trichomonas is almost always a STD, and its prevalence correlates with the overall level of sexual activity of the population studied. Recent epidemiologic surveys indicate a possible decline in prevalence. Vaginal trichomoniasis may be associated with adverse pregnancy outcomes, particularly PROM and preterm delivery. Seventy percent of men having intercourse with infected women demonstrated the organism within 48 h, while 85 percent of women whose male partners were infected developed Trichomonas infection. There is a high prevalence of gonorrhea in women with trichomoniasis. Oral contraceptives, spermicidal agents, and barrier contraceptives are all thought to reduce transmission.
Infection ranges from asymptomatic carrier state to severe, acute inflammatory disease. A vaginal discharge is reported by 50 to 75 percent of patients. It may vary in character from the classic picture of a yellow-green frothy discharge, seen in 20 to 30 percent of patients, to a gray discharge to scant or no discharge.
Other symptoms include vulvovaginal soreness and irritation (25 to 50 percent), pruritus, which may be severe (25 to 50 percent), dysuria (25 percent), and malodorous discharge (25 percent). A sense of vulvovaginal fullness may be intense or mild. As many as half of symptomatic women complain of some degree of dyspareunia. Symptoms may be more severe before, during, or after menstruation when the vaginal pH is more alkaline. Lower abdominal pain is rare and should alert the physician to the possibility of other diseases.
Just as symptoms vary in severity, so do the findings on examination. Gynecologic examination reveals the classic “strawberry cervix” secondary to diffuse punctate hemorrhages in only 2 percent of patients. Diffuse erythema is seen in 10 to 33 percent of patients.
The diagnosis is made through use of the “hanging-drop” slide test, which has a sensitivity of 80 to 90 percent in symptomatic patients. A cotton swab is used to obtain a specimen of secretions from the vaginal vault (not the endocervix) and is placed within a drop of normal saline solution on a glass slide. Microscopic examination reveals many polymorphonuclear leukocytes (PMNs) and motile, pear-shaped, flagellated trichomonads, which are slightly larger than the leukocytes. As a screening test in asymptomatic individuals, the microscopic test may only be 50 to 70 percent percent sensitive, but has virtually 100 percent specificity. Cultures are approximately 95 percent sensitive and should be considered in symptomatic patients with elevated pH, PMN excess, and absence of motile trichomonads and clue cells.
T. vaginalis may survive up to 24 h in tap water, in hot tubs, in urine, on toilet seats, and in swimming pools, but the usual sequence of events begins with a large deposit of inoculum of organisms contained in the alkaline semen at time of intercourse. Because up to 25 percent of women and 90 percent of men harboring the organisms are asymptomatic, it is difficult to control spread of disease. The cornerstone of therapy remains metronidazole. Recurrence of disease is frequent and may necessitate more than one course of treatment. There is a 90 percent cure rate with either the single- or multiple-dose regimen. Cure rates increase to more than 90 percent when sexual partners are treated simultaneously. The single-dose treatment is preferable because of lower cost, fewer side effects, and greater patient compliance. Patients not responding may require a 7-day course of therapy. Patients who are allergic may be desensitized but there is no alternative treatment that is efficacious (CDC recommendation).
Revision date: June 20, 2011
Last revised: by Sebastian Scheller, MD, ScD