How Is Trich Passed?

Trichomoniasis, often called “trich,” is a sexually transmitted infection caused by a tiny parasite. It is passed from one person to another through sexual contact, most commonly vaginal sex. The parasite travels in genital fluids, so any genital contact that exchanges those fluids can spread it.

How Is Trich Passed?

Trich is passed through unprotected vaginal sex. The parasite Trichomonas vaginalis lives in the vagina, urethra, and other genital areas. When genitals touch and fluids mix, the parasite can move from one person to another.

Penetrative sex is the main route. But the infection can also spread through vulva-to-vulva contact without penetration. This matters for people who have sex with women. The parasite does not need intercourse to transfer.

Oral sex does not appear to transmit trich. Anal sex is not a documented route either, though research is limited. The parasite prefers the warm, moist tissue of the vagina and urethra, not the mouth or rectum.

Sharing towels, toilet seats, or swimming pools does not spread trich. The parasite cannot survive long outside the body. It needs a human host to live and reproduce.

Who Gets Trich?

Trich is one of the most common sexually transmitted infections in the United States. The Centers for Disease Control and Prevention estimates that millions of new infections occur each year. Women are more likely to have symptoms than men.

Anyone who is sexually active can get trich. People with multiple partners and people who do not use condoms consistently have higher risk. Having had trich before does not protect you from getting it again. You can be reinfected after treatment.

Age matters in the data. Older women tend to have higher rates of trich compared to younger women. One reason may be that older women are less likely to use condoms if pregnancy is not a concern. Regular testing matters for this group.

Symptoms of Trichomoniasis

Many people with trich have no symptoms at all. Estimates suggest that up to 70 percent of infected people never notice anything wrong. They can still pass the parasite to partners without knowing it.

When symptoms do appear, they usually show up within 5 to 28 days after exposure. For women, the most common signs include:

• Vaginal discharge that is thin, frothy, and yellow-green in color
• A strong fishy odor
• Vaginal itching or irritation
• Pain during sex or urination

Men with symptoms typically notice urethral discharge, burning during urination, or a mild itching inside the penis. Many men have no symptoms at all. When men do have symptoms, they are often mild and easily mistaken for other conditions.

Symptoms can come and go. A person might have symptoms for a few days, then feel fine for weeks. This does not mean the infection cleared. The parasite remains until treated.

How Trich Is Diagnosed

Testing for trich requires a laboratory sample. A clinician takes a swab from the vagina or urethra. In some cases, a urine sample can be used. The sample is then examined under a microscope or tested using molecular methods.

Microscopy is fast but not always accurate. The parasite must be alive and moving to be seen this way. If the sample sits too long, the parasite dies and the test misses it.

Molecular tests, such as nucleic acid amplification tests, are more sensitive. These tests detect the parasite’s DNA and can find infections that microscopy misses. Many clinics now use these as the standard test.

If you suspect trich, ask your clinician for a specific trich test. Trich is not always included in routine STI panels. You may need to request it directly.

Treatment for Trichomoniasis

Trich is curable. The standard treatment is a single oral dose of an antibiotic called metronidazole or tinidazole. Both drugs are highly effective. Cure rates exceed 90 percent when the full dose is taken.

Alcohol must be avoided during treatment and for at least 24 hours after the last dose of metronidazole. Mixing the drug with alcohol causes severe nausea and vomiting. For tinidazole, avoid alcohol for 72 hours after the last dose.

Sexual partners need treatment at the same time. If only one person is treated, the other can pass the infection back. This is called the ping-pong effect. Both partners must finish their full course of medication even if they feel fine.

Do not have sex until both partners have completed treatment and symptoms have resolved. For most people, this means waiting about a week. Reinfection is common when partners skip treatment.

Some strains of trich have developed resistance to metronidazole. This is uncommon but possible. If standard treatment fails, a clinician may prescribe a higher dose or a longer course. A test of cure is sometimes recommended after treatment.

Complications of Untreated Trich

Untreated trich can cause problems beyond the genital area. In women, the infection increases the risk of pelvic inflammatory disease. This condition can damage the fallopian tubes and affect fertility.

Pregnant women with trich face additional risks. Some studies suggest a link between trich and preterm birth or low birth weight. If you are pregnant and have trich, treatment is important for your health and your baby’s health.

Trich also raises the risk of acquiring other sexually transmitted infections. The inflammation caused by the parasite makes it easier for HIV to enter the body. People with trich who are exposed to HIV are more likely to become infected.

Preventing Trich

Condoms are the most effective way to prevent trich. When used consistently and correctly, latex condoms block the exchange of genital fluids. This stops the parasite from moving between partners.

Internal condoms, sometimes called female condoms, also provide protection. They cover more of the vaginal area and can reduce skin-to-skin contact.

Regular testing is part of prevention. If you have a new partner or multiple partners, get tested for trich and other STIs. Many people with trich do not know they have it. Testing is the only way to know for sure.

Talking to partners about STI status is awkward but necessary. Honest conversations reduce the chance of passing an infection unknowingly. If you test positive, tell recent partners so they can get tested and treated.