Sexually transmitted diseases (STDs) caused by parasites are one of the categories into which STDs are conventionally divided (the others being STDs caused by viruses, bacteria, and fungus). The only common parasitic STD-and one of the most common STDs of any kind-that is caused by a protozoa is called trichomoniasis. Estimates of the number of new trichomoniasis cases per year in the United States alone range from five million to seven million.
The protozoa that causes trichomoniasis is of the species “Trichomonas vaginalis.” This parasite is transmitted sexually most commonly from women to men, from women to women, and from men to women. It is typically not transmitted sexually from men to men, though it’s not impossible. The organism can live outside the body briefly in a moist place, so it is also possible but uncommon for it to be transmitted via shared items such as clothing, bedding, or towels.
Trichomoniasis is often asymptomatic, and it is easily cured, so it is typically not the nightmare that some STDs can be. However, it should still be taken seriously, for multiple reasons. One, evidence indicates that sexually transmitted viruses such as the HIV virus that causes AIDS can be more easily passed to and from a woman with trichomoniasis. Two, pregnant women with trichomoniasis are more likely to deliver prematurely or to give birth to a low birthweight baby. Three, for those people with trichomoniasis who are symptomatic, especially women, the symptoms can be quite unpleasant and uncomfortable.
Where there are symptoms, they generally occur within 3 to 28 days. Most men are not symptomatic, but for those who are, the symptoms can include a mild pain or burning sensation during or after urination or ejaculation, discharge from the penis, or a tingling in the penis.
Women are more often, though not always, symptomatic. Women’s symptoms can include a frothy, vaginal discharge with a strong odor; genital burning, itching, or redness; pain during or after intercourse or urination; or abdominal pain.
The most common treatment for trichomoniasis is one megadose pill of the antibiotic metronidazole. Another antibiotic sometimes prescribed is tinidazole. Rather than a megadose, antibiotics are sometimes given in smaller doses 2-3 times a day for 7-10 days. There are also medicated creams or gels that can be used in the vagina to treat the infection, but they tend not to be as effective as the oral antibiotics.
When a person is treated for trichomoniasis it is important that their sex partner(s) be treated at the same time. Otherwise the protozoa could be transmitted right back to the person.
Elizabeth Boskey, “Trichomoniasis.” About.com.
“Trichomoniasis.” Mayo Clinic.