Trichomonas vaginalis-No Longer A Minor STD

IN THIS ISSUE Hobbs et al.1 describe a greater than 17% prevalence of Trichomonas vaginalis in men attending sexually transmitted disease (STD) and dermatology clinics in Malawi. These data add to an all too slowly growing body of T. vaginalis research which, taken in aggregate, suggests that the time has come to encourage increased investigation of this common sexually transmitted protozoan. The paper by Hobbs et al. illuminates three important facets of T. vaginalis morbidity in men. First, the high prevalence of infection in men helps to emphasize that trichomoniasis is not only a source of morbidity in women. Early studies found T. vaginalis to be the causal agent of nongonococcal urethritis in less than 5% of men with the syndrome.2 More recently, as chlamydial infection rates have declined, the proportion of nongonococcal urethritis attributable to trichomoniasis appears to be increasing and accounts for as much as 17% of nonchlamydial nongonococcal urethritis,3 a finding which lead to the recommendation of inclusion of trichomoniasis therapy for men with recurrent nongonococcal urethritis.4 Nonetheless, as in women 10% to 50% of trichomoniasis in men may also be asymptomatic. Clearly, T. vaginalis in not a rare STD in men. Second, in this study, human immunodeficiency virus (HIV)-infected men with symptomatic trichomonas urethritis had an approximately sixfold increased HIV concentration in semen as compared to men without urethritis, thereby suggesting an important role for the organism in the continuing male to female spread of HIV. The increased HIV concentrations in men with T. vaginalis urethritis are similar in magnitude to increments described for men with gonococcal urethritis.5 Third, the investigators used both nucleic acid amplification tests (polymerase chain reaction [PCR]) and an easily used culture system to diagnose trichomoniasis, demonstrating that the infection may be readily diagnosed in males with a high degree of sensitivity/specificity. Although these findings are important contributions to our understanding regarding the spectrum of illness attributable to trichomoniasis in men, they only add to an increasingly compelling body of evidence which suggests the need for further investigation of trichomoniasis epidemiology, treatment, and diagnosis to assist implementation of control strategies. Numerically, trichomoniasis has never been a minor STD, at least for women. Recent estimates confirm that trichomoniasis is the most common curable STD among sexually active women, causing about 5,000,000 new cases per year.6 Thus, the sheer volume of this disease in women warrants attention and reflection regarding control strategies. As efforts to define chlamydial prevalence in different male populations proceed, estimates of disease burden could likely also increase. As well as being a common STD, trichomoniasis may also contribute to long-lasting morbidity for women and children born to infected mothers. Several African studies have found vaginal trichomoniasis, like other STDs, to be associated with increased risk for HIV infection.7,8 Furthermore, limited data have been available for years suggesting a role for T. vaginalis in causation of prematurity and delivery of low-birth-weight infants, some of the same serious reproductive health consequences used to argue for the importance of control of other treatable STDs. In one of the more recent studies, Cotch et al.9 found that trichomoniasis was associated with a 30% increase in preterm birth and low birth weight. Given the ease of testing and treatment, efforts should be made to assure routine inclusion of trichomoniasis care in pregnancy. Finally, as a target for intervention, available albeit underutilized tools make trichomonas control a readily attainable, realistic goal. There is little reason why clinicians should continue to accept wet-mount microscopy as an appropriate diagnostic standard for evaluation of trichomoniasis in women. Studies have repeatedly demonstrated that wet mount microscopy has a sensitivity of only 60 to 80% when compared to culture diagnosis.10–12 We now have a readily affordable (less than $3.00 per test device), highly sensitive culture system for T. vaginalis which permits accurate diagnosis of trichomoniasis.10–12 Thus, while wet-mount microscopy may continue to be a useful part of testing algorithms or to guide immediate therapy for women with trichomoniasis, it seems that the time is right to implement routine culture diagnosis, including screening, for trichomoniasis in reproductive health settings. The cost is modest, and the potential benefits are likely to be substantial. Similarly, for most individuals, treatment of trichomoniasis is readily affordable and easily accomplished. A single 2-gm dose of metronidazole is judged to be highly effective therapy for the infection,4 and cost of treatment is less than $7.00 (cost to the pharmacist of 2.0 g of metronidazole is $2.25). There remains much to be known about T. vaginalis and the spectrum of disease caused by it. Potential research areas include evaluation of the natural history of asymptomatic infection, better delineation of the prevalence of infection in the general population, control strategies, and vaccine development (a partially effective veterinary vaccine is already available and reduces spontaneous abortion in cattle.13 New tools such as the nucleic acid amplification tests utilized by Hobbs et al.1 are similar to those used by others14 and provide new opportunities to better study the epidemiology and biology of this widespread pathogen. At the same time, we currently know enough to begin to plan and initiate trichomonas control programs based on use of currently available diagnostic and therapeutic modalities. Increasing reports of metronidazole-resistant T. vaginalis15 suggest that the research agenda for trichomoniasis should explore alternate therapies for this organism. Trichomoniasis should no longer be considered a minor STD, nor a problem whose impact in limited to women.