Literature review > Issue_2 > Review Wendel et al. 

Trichomonas vaginalis has long been an "orphan pathogen" (poorly understood, under funded, often untreated) whose time may have finally arrived. Trichomonas is remarkably prevalent in developed and developing countries, in both men and women. Many studies have suggested that trichomonas infections could play a significant role in the sexual transmission of HIV.

Detection of trichomonas in a clinic setting depends on visual recognition in a fresh vaginal specimen (wet-mount preparations), a technique with limited sensitivity. Culture of trichomonas has better sensitivity, but the technique is more cumbersome and labor intensive. Men are rarely examined or treated, regardless of high prevalence [1, 2].

In one of many studies to bemoan the status of trichomonas, Wendel et al. compared wet preparations, PCR, and culture in "high risk" women attending Baltimore City STD Clinics. The study cohort included 337 women, most of whom (70%) had symptoms. As expected, T. vaginalis infection was common (detected in 29% of women). PCR had a sensitivity of 84% and specificity of 94%, generally consistent with other studies [3-8]. The results demonstrate that treatment of T. vaginalis would have increased from 69% to 84% if PCR results had been available.

Trichomonas is a prevalent STD pathogen that will not go away because we ignore it. Does the solution to the problem really rest in diagnostic technology? Commercial antigen detection tests can now be used to bypass wet preparations, but such assays are not significantly more sensitive than wet preparations and have not been used in men. While PCR and culture have excellent specificity and much greater sensitivity, it seems unlikely that clinicians will clamor for their usage, give the low status of trichomonas.

Perhaps the solution to trichomonas infection lies in promoting different management schemes, such as targeted screening, syndromic management, or a combination of the two. In targeted screening, trichomonas infection would only be sought in people (men and women) with recognized risk factors associated with an increased pretest probability of infection. In syndromic treatment, people at risk would receive empiric therapy, taking advantage of the low cost and safety of a single dose of metronidazole. Indeed, in our own recent study of men with urethritis in Malawi (in whom prevalence of trichomonas approaches 20%) we concluded that empirical therapy with metronidazole was probably warranted [9].

PCR detection assays for T. vaginalis have been useful tools for heightening awareness of the tremendous prevalence of this sexually transmitted infection. These tests may lead to improved treatment, especially in developed countries. However, global management and control of trichomonas infections may well depend on our success in "spreading the word" and employing novel screening and treatment strategies.

References:

1. Bowden FJ, Garnett GP. Why is Trichomonas vaginalis ignored? Sexually Transmitted Infections 1999;75:372-4.

2. Hook EW, 3rd. Trichomonas vaginalis--no longer a minor STD. Sexually Transmitted Diseases 1999;26:388-9.

3. Lawing LF, Hedges SR, Schwebke JR. Detection of trichomonosis in vaginal and urine specimens from women by culture and PCR. Journal of Clinical Microbiology 2000;38:3585-3588.

4. Madico G, Quinn TC, Rompalo A, McKee KT, Jr., Gaydos CA. Diagnosis of Trichomonas vaginalis infection by PCR using vaginal swab samples. Journal of Clinical Microbiology 1998;36:3205-10.

5. Heine RP, Wiesenfeld HC, Sweet RL, Witkin SS. Polymerase chain reaction analysis of distal vaginal specimens: a less invasive strategy for detection of Trichomonas vaginalis. Clinical Infectious Diseases 1997;24:985-7.

6. Kaydos SC, Swygard H, Wise SL, Sena AC, Leone PA, Miller WC, Cohen MS, Hobbs MM. Development and validation of a PCR-based enzyme-linked immunosorbent assay with urine for use in clinical research settings to detect Trichomonas vaginalis in women. J. Clin. Microbiol. 2002;40:89-95.

7. Mayta H, Gilman RH, Calderon MM, Gottlieb A, Soto G, Tuero I, Sanchez S, Vivar A. 18S ribosomal DNA-based PCR for diagnosis of Trichomonas vaginalis. Journal of Clinical Microbiology 2000;38:2683-2687.

8. van Der Schee C, van Belkum A, Zwijgers L, van Der Brugge E, O'Neill E L, Luijendijk A, van Rijsoort-Vos T, van Der Meijden WI, Verbrugh H, Sluiters HJ. Improved diagnosis of Trichomonas vaginalis infection by PCR using vaginal swabs and urine specimens compared to diagnosis by wet mount microscopy, culture, and fluorescent staining. Journal of Clinical Microbiology 1999;37:4127-30.

9. Price MA, Zimba D, Hoffman IF, Kaydos-Daniels SC, Miller WC, Martinson F,
Chilongozi D, Kip E, Msowoya E, Hobbs MM, Kazembe PN, Cohen MS. The
addition of treatment for trichomoniasis to the syndromic management of
urethritis in Malawi: A randomized clinical trial. Sexually Transmitted Diseases
2003;in press.

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