Tricomonas veginalis

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"Trichomonas vaginalis"

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CDC Trichomoniasis STI Treatment Guidelines Trichomonas vaginalis

Trichomonas vaginalis is a protozoan parasite that causes trichomoniasis, a common sexually transmitted infection (STI).
  • In women: may cause frothy yellow-green or thin vaginal discharge, unpleasant odor, itching/burning, pain when urinating, or discomfort during sex. Many people have no symptoms.
  • In men: often no symptoms, but it can cause urethral irritation, burning after urination/ejaculation, or discharge.
  • Diagnosis: a clinician can test a vaginal swab or urine sample, usually with a nucleic-acid test.
  • Treatment: prescription oral antibiotics are needed, typically metronidazole. CDC guidance recommends metronidazole 500 mg by mouth twice daily for 7 days for women; men are often treated with a single 2 g oral dose. The correct regimen depends on sex, pregnancy, HIV status, prior treatment, and allergies. See the CDC trichomoniasis guideline.
  • Partners must be treated at the same time, even if they have no symptoms. Avoid sex until everyone has completed treatment and symptoms have resolved.
  • Women should be retested about 3 months after treatment because reinfection is common, per the CDC follow-up advice.
Trichomoniasis is treatable, but it should not be self-treated with leftover antibiotics. A recent systematic review also confirms that it remains a significant global STI.

Morphology of the trichomonas vaginals

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Trichomonas vaginalis trophozoite microscopy morphology flagella undulating membrane

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"Trichomonas vaginalis" morphology

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Trichomonas vaginalis morphology trophozoite flagella undulating membrane CDC DPDx

Morphology of Trichomonas vaginalis

  • Exists only as a trophozoite. It has no cyst stage.
  • Shape: pear-shaped or oval, with a pointed posterior end.
  • Size: approximately 7-23 µm long and 5-15 µm wide.
  • Nucleus: single, oval nucleus located near the anterior end.
  • Flagella: five flagella:
    • Four anterior flagella project freely from the front.
    • One recurrent flagellum runs backward along the body.
  • Undulating membrane: a short membrane formed along the anterior half of the organism by the recurrent flagellum.
  • Axostyle: a prominent rod-like structure that runs through the body and projects from the posterior end.
  • Motility: rapid, jerky or tumbling movement, demonstrable in a fresh saline wet mount.
  • Cytostome: absent.
Exam description:
A pear-shaped, flagellated trophozoite with four anterior flagella, one recurrent flagellum forming a short undulating membrane, a single anterior nucleus, and a posteriorly projecting axostyle. No cyst form occurs.
Motile trophozoites can be demonstrated in vaginal or urethral secretions, and sometimes urine, by wet-mount microscopy, as described by CDC DPDx guidance.
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