Trichomonas vaginalis: Pathogenesis, diagnosis and treatment

Trichomonas vaginalis: Pathogenesis, diagnosis and treatment

Trichomonas vaginalis: Pathogenesis, diagnosis and treatment

It is a pear-shaped organism with a central nucleus and four anterior flagella; and undulating membrane extends about two-thirds of its length. It exists only as a trophozoite form, and measured 7-23μm long and 5-15μm wide. Transmission is by sexual intercourse.


The trophozoite is found in the urethra and vagina of women and the urethra and prostate gland of men. After introduction by sexual intercourse, proliferation begins which results in inflammation and large numbers of trophozoites in the tissues and the secretions. The onset of symptoms such as vaginal or vulval pruritus and discharge is often sudden and occurs during or after menstruation as a result of the increased vaginal acidity.  The vaginal secretions are liquors, greenish or yellowish, sometimes frothy, and foul smelling. Infection in the male may be latent, with no symptoms, or may be present as self-limited, persistent, or recurring urethritis.



This parasite has worldwide distribution, and sexual intercourse is the primary mode of transmission. Occasionally, infections can be transmitted by fomites (toilet articles, clothing), although this transmission is limited by liability of the trophozoite. Rarely Infants may be infected by passage through the mother’s infected birth canal. The prevalence of this flagellate in developing countries is reported to be 5% –20% in women and 2% –10% in men.

Clinical disease – trichomoniasis.

Most infected women at the acute stage are asymptomatic or have a scanty, watery vaginal discharge. In symptomatic cases vaginitis occurs with more extensive inflammation, along with erosion of epithelial lining, and painful urination, and results in symptomatic vaginal discharge, vulvitis and dysuria.


The infection may induce humoral, secretory, and cellular immune reactions, but they are of little diagnostic help and do not appear to produce clinically significant immunity.

Laboratory diagnosis

• In females, T.vaginalis may be found in urine sediment, wet preparations of vaginal secretions or vaginal scrapings.

• In males it may be found in urine, wet preparations of prostatic secretions or following massage of the prostate gland.


• Contamination of the specimen with faeces may confuse T.vaginalis with T.hominis.


Metronidazole is the drug of choice. If resistant cases occur, re-treatment with higher doses is required.


– Both male and female sex partners must be treated to avoid reinfection

– Good personal hygiene, avoidance of shared toilet articles and clothing.

– Safe sexual practice.


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