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[Trichomonas vaginalis]

Causal Agent

Trichomonas vaginalis, a flagellate, is the most common pathogenic protozoan of humans in industrialized countries.

Life Cycle


Trichomonas vaginalis resides in the female lower genital tract and the male urethra and prostate The number 1, where it replicates by binary fission The number 2. The parasite does not appear to have a cyst form, and does not survive well in the external environment. Trichomonas vaginalis is transmitted among humans, its only known host, primarily by sexual intercourse The number 3.

Geographic Distribution

Worldwide. Higher prevalence among persons with multiple sexual partners or other venereal diseases.

Clinical Presentation

Trichomonas vaginalis infection in women is frequently symptomatic. Vaginitis with a purulent discharge is the prominent symptom, and can be accompanied by vulvar and cervical lesions, abdominal pain, dysuria and dyspareunia. The incubation period is 5 to 28 days. In men, the infection is frequently asymptomatic; occasionally, urethritis, epididymitis, and prostatitis can occur.

Trichomonas vaginalis trophozoites.


Trophozoites of Trichomonas vaginalis are pyriform and 7-30 ┬Ám long. They have five flagella: four anteriorly directed flagella and one posteriorly along the outer membrane of the undulating membrane. The large nucleus is usually located at the wider, anterior end and contains many chromatin granules and a small karyosome. The cytoplasm also contains many granules, but these are often not seen in Giemsa-stained specimens.
	Figure A

Figure A: Two trophozoites of T. vaginalis obtained from in vitro culture, stained with Giemsa.

	Figure B

Figure B: Trophozoite of T. vaginalis in a vaginal smear, stained with Giemsa.

	Figure C

Figure C: Trophozoite of T. vaginalis in a vaginal smear, stained with Giemsa.

	Figure D

Figure D: Trophozoite of T. vaginalis in a vaginal smear, stained with Giemsa.

Laboratory Diagnosis

Microscopic examination of wet mounts may establish the diagnosis by detecting actively motile organisms. This is the most practical and rapid method of diagnosis (allowing immediate treatment), but it is relatively insensitive. Direct immunofluorescent antibody staining is more sensitive than wet mounts, but technically more complex. Culture of the parasite is the most sensitive method, but results are not available for 3 to 7 days. In women, examination should be performed on vaginal and urethral secretions. In men, anterior urethral or prostatic secretions should be examined.

Treatment Information

Trichomoniasis can be cured with a single dose of prescription antibiotic medication (either metronidazole or tinidazole), pills which can be taken by mouth. It is okay for pregnant women to take this medication. Some people who drink alcohol within 24 hours after taking this kind of antibiotic can have uncomfortable side effects.

People who have been treated for trichomoniasis can get it again. About 1 in 5 people get infected again within 3 months after treatment. To avoid getting reinfected, make sure that all of your sex partners get treated too, and wait to have sex again until all of your symptoms go away (about a week). Get checked again if your symptoms come back.

DPDx is an education resource designed for health professionals and laboratory scientists. For an overview including prevention and control visit

  • Page last reviewed: May 3, 2016
  • Page last updated: May 3, 2016
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