What is Trichomonas Vaginalis?

Trichomonas vaginalis, or T. vaginalis, is a single-celled organism which causes trichamoniasis, a sexually transmitted disease and respiratory that infects both men and women. Trichamoniasis is among the most common infections in developed countries, and over 180 million new cases are reported annually worldwide. Trichamoniasis is generally treated successfully with oral antibiotics.

T. vaginalis is a large, oval-shaped single cell, which measures about 9x7 micrometers (µm). To understand the size of one of these cells, one micrometer is 1,000 times smaller than a millimeter, and red blood cells usually have a diameter of 8 µm. Each T. vaginalis cell contains five whip-like structures called flagella, and a barb-like structure called an axostyle. Flagella are used to help propel the organism through fluid, while the axostyle is often used as a way to attach to the surface of other cells, and damages tissue upon infection.

Trichomonas vaginalis most commonly infects the vagina, but can also infect the urinary tract and fallopian tubes, as well as structures in the airways, causing pneumonia. Infection occurs when the pH balance of the vagina shifts from acidic to slightly basic and allows growth of Trichomonas vaginalis cells. These cells can survive up to 24 hours in urine, semen or water, and can survive on a number of materials for a few hours, which means a person can be infected by coming in contact with infected material.


Vaginal infection can result in abnormal secretions and itching. It may also cause what is known as a “strawberry cervix” or vagina, which is a result of the tissue damage inflicted by Trichomonas vaginalis. If greenish-yellow frothy discharge or discomfort is reported by a patient, the doctor will order a test for T. vaginalis. Trichomonas can be diagnosed by overnight culture or via a pap smear.

In a pap smear, infection is indicated when stain tissue reveals an abundance of the small T. vaginalis cells. Additionally, infected host cells will show a transparent halo around their nucleus, the region of the cell that contains DNA. Corkscrew motility of the single cells, corresponding to the locomotion of Trichomonas, can also be an indicator of infection. The most commonly used method of diagnosis is overnight culturing, a test for the growth of Trichomonas vaginalis, because it is much more sensitive for detecting infection.

Trichomonas can be carried by males, who usually don’t show any symptoms, which means an infected individual may have no knowledge of the infection. As such, the use of condoms during sexual activity can significantly decrease the risk of contracting Trichamoniasis from a carrier. Once Trichamoniasis has been diagnosed, it is important to notify past sexual partners and instruct them to get tested. Additionally, it is important for any current partner to seek treatment because he or she may be an asymptomatic carrier capable of re-infecting new partners. If left untreated, Trichomonas vaginalis increases the risk for other sexually transmitted diseases, including HIV.


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