Trichomoniasis (often called trich) is a sexually transmitted disease.  It is caused by a parasite called Trichomonas vaginalis, which is a protozoa made of just one cell. Trichomoniasis can affect both men and women.  It is usually an infection of the urinary system and genitals.

Cause
The Trichomonas vaginalis parasite can only live in the human genital tract.  Trichomoniasis is only spread through sex, or if two people's genitals touch.

Signs and symptoms
Most people with trichomoniasis do not have any symptoms. 

When people do have symptoms, they usually start about 5 to 28 days after the person got infected.  Symptoms may include:
 Pain, burning, or itching in the urethra (urethritis), the vagina (vaginitis), or the penis
 Pain while having sex (dyspareunia)
 Women may have a yellow-green, badly-smelling vaginal discharge
 Lower abdominal pain (this does not happen often)

Complications
Complications are serious problems that can happen because a person has a disease.  These problems do not happen to everyone with trichomoniasis.  They are the most serious problems that trichomoniasis can cause.  Some of the most dangerous problems that can happen to a person with trichomoniasis include:
 People with trichomoniasis are more likely to get (or spread) HIV, the virus that causes AIDS.
 If a woman is pregnant, trichomoniasis can cause her to have a premature infant, or an infant that weighs less than normal.
 Trichomoniasis may work together with human papillomavirus (HPV) to cause cervical cancer, although this has not been proven.
 In men, trichomoniasis can cause inflammation (swelling) of the urethra and the prostate.  In the prostate, trichomoniasis may create chronic (long-term) inflammation that may eventually cause prostate cancer.

Treatment
Treatment for trichomoniasis is usually metronidazole (Flagyl), which kills protozoa like Trichomonas vaginalis.  However, this medication has to be used carefully with woman who are in the early stages of pregnancy.  Anyone the infected person has had sex with should also get treatment, even if they have no symptoms.

About 95% to 97% of people with trichomoniasis are cured after one dose of metronidazole.  

Without treatment, trichomoniasis can stay in a woman's body for months to years.  In many (but not all) men, it seems to go away on its own.

Prevention
Trichomoniasis can be prevented by having safe sex (for example, by using condoms).

The United States Centers for Disease Control and Prevention (CDC) suggests that women who are having vaginal discharge should get tested for trichomoniasis.

How common is trichomoniasis?
Trichomoniasis is the most common sexually transmitted disease in the world that is not caused by a virus.  Every year, about 248 million more people get trichomoniasis.  It is more common in women than men. 

It is also the most common non-viral sexually transmitted disease in the United States.  In the U.S., about 3.7 million people have trichomoniasis, and about 1.1 million more people get infected every year.  Recent research has said that 3% of the U.S. population (3 in every 100 people) have trichomoniasis.  In people who are at higher risk of getting trichomoniasis, like people with HIV and people in prison, between 7.5% to 32% are infected.

Related pages
 Sexually transmitted disease
 Safe sex
 Parasite

References

Sexually transmitted diseases