Trichomoniasis is a sexually transmitted disease, which produces a vaginitis with pain, discharge, and dysuria. The infection fluctuates over weeks to months. Men are usually asymptomatic but may have urethritis or prostatitis.
Trichomoniasis is a cosmopolitan disease usually transmitted by sexual intercourse. It is estimated that 3 million women in the United States and 180 million worldwide acquire this disease annually, and 25% of sexually active women become infected at some time during their lives; 30 to 70% of their male sexual partners are also parasitized, at least transiently. As would be expected, the likelihood of acquiring the disease correlates di-rectly with the number of sexual contacts. Infection is rare in adult virgins, whereas rates as high as 70% are seen among prostitutes, sexual partners of infected patients, and indi-viduals with other venereal diseases. In women, the peak incidence is between 16 and 35 years of age, but there is a relatively high prevalence in the 30- to 50-year age group.
Nonvenereal transmission is uncommon. Transfer of organisms on shared washcloths may explain, in part, the high frequency of infection seen among institutionalized women. Female neonates are occasionally noted to harbor T. vaginalis, presumably acquiring it during passage through the birth canal. High levels of maternal estrogen produce a transient decrease in the vaginal pH of the child, rendering it more susceptible to colonization. Within a few weeks, estrogen levels drop, the vagina assumes its premenar- cheal state, and the parasite is eliminated.
Direct contact of T. vaginalis with the squamous epithelium of the genitourinary tract results in destruction of the involved epithelial cells and the development of a neutrophilic inflammatory reaction and petechial hemorrhages. The precise pathogenesis of these changes is unknown. The organism is not invasive, and extracellular toxins have never been demonstrated. The expression of a 200-kd parasitic glycoprotein, however, has been found to correlate with clinical manifestations. Changes in the microbial, hormonal, and pH environment of the vagina as well as factors inherent to the infecting parasite are thought to modulate the severity of the pathologic changes. Although humoral, secretory, and cellular immune reactions can be demonstrated in most infected women, they are of little diagnostic help and do not appear to produce clinically significant immunity.