Trichomonas: A single-celled protozoan parasite best known in medicine because one species causes vaginitis (vaginal inflammation). Infection with trichomonas (trichomoniasis) is the most common curable sexually transmitted disease (STD) in young sexually active women.) in young sexually active women. The species of trichomonas responsible for STD is Trichomonas vaginalis. The vagina is the most common site of infection in women, and the urethra (urine canal) is the most common site of infection in men. The parasite is sexually transmitted through penis-to-vagina intercourse or vulva-to-vulva (the genital area outside the vagina) contact with an infected partner. Women can acquire the disease from infected men or women, but men usually contract it only from infected women.
Men and women differ in their response to the infection. Most men with trichomoniasis have no signs or symptoms; however, some men may have an irritation inside the penis, mild discharge, or slight burning after urination or ejaculation. Many women have signs or symptoms of infection which include a frothy, yellow-green vaginal discharge with a strong odor. The infection also may cause discomfort during intercourse and urination, as well as irritation and itching of the female genital area. In rare cases, lower abdominal pain can occur. Symptoms usually appear in women within 5 to 28 days of exposure.
The genital inflammation caused by trichomoniasis increases a woman's susceptibility to HIV infection. Having trichomoniasis also increases the chances a woman can pass HIV to her sex partners. Trichomonas also affects pregnancy. Pregnant women with trichomoniasis may have babies who are born early or with low birth weight (less than five pounds).
The parasite is harder to detect in men than in women. In women, a pelvic examination can reveal small red ulcerations (sores) on the vaginal wall or cervix. Treatment is usually with the drug metronidazole given by mouth in a single dose. The symptoms of trichomoniasis in infected men may disappear within a few weeks without treatment. However, an infected man, even a man who has never had symptoms or whose symptoms have stopped, can continue to infect a female partner until he has been treated. Therefore, both partners should be treated at the same time to eliminate the parasite. Persons being treated for trichomoniasis should avoid sex until they and their sex partners complete treatment and have no symptoms. Metronidazole can be used by pregnant women. Having trichomoniasis once does not protect a person from getting it again. Following successful treatment, people can still be susceptible to re-infection. Latex condoms, when used consistently and correctly, can reduce the risk of transmission of trichomoniasis.