Trichomoniasis (Trichomonas vaginalis)

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Chapter 276 Trichomoniasis (Trichomonas vaginalis)

Trichomoniasis, caused by the protozoan parasite Trichomonas vaginalis, is the most common nonviral sexually transmitted disease worldwide. It primarily causes vulvovaginitis in women but has been implicated in pelvic inflammatory disease, adverse outcomes in pregnancy, chronic prostatitis, and an increased risk of transmission of HIV.

Pathogenesis

T. vaginalis is an anaerobic, flagellated protozoan parasite. Infected vaginal secretions contain 101 to 105 or more protozoa/mL. T. vaginalis is pear shaped and exhibits characteristic twitching motility in wet mount (Fig. 276-1). Reproduction is by binary fission. It exists only as vegetative cells; cyst forms have not been described. T. vaginalis damages host cells and tissues by a number of mechanisms. Adhesion molecules allow attachment of T. vaginalis to host cells, and hydrolases, proteases, and cytotoxic molecules act to destroy or impair the integrity of host cells. Parasite-specific antibodies and lymphocyte priming occur in response to infection, but durable protective immunity does not occur.

image

Figure 276-1 Trichomonas vaginalis trophozoites stained with Giemsa (left) and iron hematoxylin (right).

(From the Centers for Disease Control and Prevention: Laboratory identification of parasites of public health concern. Trichomoniasis (website). www.dpd.cdc.gov/dpdx/HTML/ImageLibrary/Trichomoniasis_il.htm. Accessed August 30, 2010.)