Answer to the Parasite Case of the Week 713: Trichomonas vaginalis trophozoite
As noted by Florida Fan, the Giemsa-stained preparation is ideal for highlighting the key morphologic features of T. vaginalis trophozoites, including the flagella, undulating membrane, and axostyle. In my mind, the Pap stain just doesn't highlight the features as well. Here is an annotated image showing some of these features:
The trophozoites of T. vaginalis are 7-30 micrometers long, are tear drop/pear-shaped (i.e., pyriform), and have 5 flagella. Four flagella are anteriorly directed, while the 5th flagellum runs posteriorly along the undulating membrane. The nucleus is ovoid and there may be visible granules in the cytoplasm.
Trophozoites infect the squamous epithelial cells of the lower female genitourinary tract, as well as the male urethra and prostate. Historically, it was thought that only a trophozoite form existed, and thus transmission could only be sustained through direct intimate contact (and possibly through shared fomites). However, cyst-like structures (CLS) which can survive exposure to detergents, certain chemicals (e.g., chlorine) and dessication were described in 2020, thus raising the potential for non-sexual transmission. Further studies are needed to better understand this potential transmission route.
1 comment:
Detailed/correct Morphology is critical. Other trichomonads from the gut can contaminate the external genitalia and wrongly implicate sexual exposure. This is particularly important in prepubertal females as it may be taken as sexual abuse. If in doubt, confirm by PCR, now available in many labs.
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