Trichomonas vaginalis

Causative agent of trichomonosis

■ Trichomonas vaginalis is a frequent flagellate species that occurs worldwide and is transmitted mainly by sexual intercourse. It causes vaginitis in women and urethritis in men. ■

Occurrence. The number of new cases is estimated at 170 million annually (WHO, 1998). In average populations of developed countries, infection rates are about 5-20% in women and usually below 5% in men.

Parasite, life cycle, and epidemiology. Trichomonas vaginalis is a pear-shaped protozoon about 10-20 im long and 2-14 im wide (Fig. 9.2). Five flagella emerge from a basal body at the anterior pole, four freely extend forwards and one extends backwards, forming the outer edge of the undulating membrane, which reaches back only just beyond the middle of the cell. An axial rod made up of microtubules (the axostyle) protrudes with its free tip from the posterior end of the cell. The oval cell nucleus lies near the upper pole of the protozoon. Trichomonads are anaerobic protozoa that possess hydrogenosomes, which are specialized organelles producing H2 as a metabolite.

T. vaginalis colonizes the mucosa of the urogenital tract and reproduces by longitudinal binary fission. Trichomonads do not encyst, although rounded, nonmotile forms are observed which are degenerated stages without epide-miological significance.

— Trichomonas vaginalis

Basal body Nucleus Hydrogenosomes

Anterior flagella

— Trichomonas vaginalis

Basal body Nucleus Hydrogenosomes

Anterior flagella

Basal Body And Parabasal Body

Trailing flagellum and undulating membrane

Costa

Parabasal body and Golgi apparatus

Fig. 9.2. Morphology of Trichomonas vaginalis (schematic).

Trailing flagellum and undulating membrane

Costa

Parabasal body and Golgi apparatus

Fig. 9.2. Morphology of Trichomonas vaginalis (schematic).

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