Trichomoniasis — Symptoms, Testing, Treatment

Trichomoniasis ("trich") is the most common curable STI in the United States — and the one most often missed. It affects an estimated 2.6 million Americans, mostly women, and it isn't included in routine STI panels in many clinics. Symptoms are subtle, and partner treatment is essential.

Here's the full practical picture.

The short answer

• What it is: A parasitic STI caused by Trichomonas vaginalis (a protozoan, not a bacterium)
• How common: About 2.6 million US cases — most common curable STI
• Mostly affects: Women (men are usually asymptomatic carriers)
• Main symptoms: Itching, frothy yellow-green discharge, odor in women; usually asymptomatic in men
• Testing: Vaginal swab NAAT (women); urine NAAT (men) — must be specifically requested
• Treatment: Single dose of metronidazole or tinidazole; current guidelines favor 7-day course for women
• Partner treatment: Essential; reinfection common

What trichomoniasis looks like

In women

• Itching, irritation in vulva and vagina
• Frothy, yellow-green or yellow vaginal discharge (classic, not always present)
• Strong, sometimes musty odor
• Painful urination
• Pain during sex
• Sometimes "strawberry cervix" — red spots on cervix during pelvic exam
• About 70% of infections are symptomatic to some degree

In men

• Usually asymptomatic
• When symptoms: mild urethritis (slight discharge, burning), often vague
• About 70-90% of men are completely asymptomatic — they're silent carriers

Atypical patterns

• Sometimes mistaken for BV (similar odor) or yeast (similar itching)
• Some women have only mild itching
• Sometimes only diagnosed by exam findings

How it spreads

• Sexual contact (vaginal, oral, occasionally anal)
• Direct genital contact even without intercourse
• NOT usually spread through:
  • Toilet seats
  • Shared towels (rarely — trich can survive briefly on damp surfaces)
  • Sharing utensils, food
  • Casual contact

Incubation: 5-28 days typically.

How it's tested

NAAT (gold standard)

• Vaginal swab (women — most sensitive)
• Urine NAAT (men — somewhat less sensitive)
• Same lab process as chlamydia/gonorrhea NAAT
• Results in 1-3 days

Microscopy (wet mount)

• Older method; provider examines vaginal sample under microscope
• Less sensitive (50-70%) than NAAT
• Done same-visit; results immediate
• Still useful when NAAT isn't available

Antigen tests

• OSOM Trichomonas Rapid Test — provider-administered, results in 10 minutes
• Available in some clinics

Why it's often missed

• Not in basic STI panels (HIV, syphilis, chlamydia, gonorrhea)
• Men are mostly asymptomatic — no reason for them to test
• Wet mount has variable sensitivity
• Sometimes labeled as "atypical BV" without explicit testing

CDC screening recommendations

• Routine screening: All HIV+ women annually
• High-risk groups: Women with multiple partners, exchange of sex for money/drugs, history of trichomoniasis
• Asymptomatic but exposed: Test if known partner with trich
• Asymptomatic general population: Not routinely recommended

But many clinicians argue this is too restrictive given prevalence and partner treatment needs.

Treatment

Women (current recommendations, 2021 guidelines)

• Metronidazole 500 mg twice daily for 7 days (preferred)
• Or tinidazole 2 g single dose (alternative)
• The 7-day metronidazole regimen reduces reinfection vs the single 2g dose

Men

• Metronidazole 2 g single dose OR
• Tinidazole 2 g single dose

Pregnancy

• Metronidazole 500 mg twice daily for 7 days is safe in pregnancy
• Tinidazole avoided in first trimester
• Some older concern about first-trimester metronidazole has been largely retracted

Allergic to metronidazole?

• Desensitization protocol exists
• Topical treatment is NOT effective for trichomoniasis
• Tinidazole is structurally similar — same allergy risk

Important precautions

• Avoid alcohol for 24-72 hours during and after treatment (disulfiram-like reaction)
• Take with food to reduce nausea

After treatment

• Avoid sex for 7 days after starting treatment AND until partner is treated
• Retest at 3 months — reinfection common (8-25% in 3 months)
• Test of cure not routinely needed unless symptoms persist or persistent partner exposure

Partner treatment

• Sex partners from the past 60 days should be:
  • Tested AND treated, OR
  • Treated empirically (presumptively, without testing)
• This is essential to prevent reinfection
• "Expedited partner therapy" (you take medication for your partner) is widely available

Trichomoniasis and other STIs

• Often co-occurs with: BV, chlamydia, gonorrhea, HIV
• Trichomoniasis increases HIV acquisition and transmission risk
• HPV co-infection is common
• Increases risk of preterm birth and low birth weight in pregnancy

Resistant trichomoniasis

About 4-10% of trichomoniasis cases have reduced susceptibility to metronidazole. Indicators:

• Persistent symptoms despite full treatment
• Recurrent infections without clear reinfection source
• Confirmed treatment failure

Approach:

• Switch to tinidazole (often effective when metronidazole isn't)
• Higher-dose, longer courses
• Specialty consultation if continues to fail

What trichomoniasis is NOT

• Not a virus
• Not a bacterium
• Not transmissible through casual contact
• Not curable with OTC products
• Not the same as Mycoplasma genitalium (also an STI but different)

Trichomoniasis vs BV vs yeast — side by side

See BV vs yeast vs STI for more.

Special considerations

HIV+ patients

• Routine annual trichomoniasis screening recommended
• Treatment longer course (500mg BID x 7d) preferred over single dose
• Higher rates of recurrence

Pregnancy

• Safe to treat with metronidazole
• Untreated trichomoniasis associated with preterm birth, low birth weight, premature rupture of membranes
• Some debate about routine screening in pregnancy — discuss with provider

Postmenopausal women

• Less common but still occurs
• Symptoms can be subtle
• Diagnosis often delayed

Common misconceptions

"I'd know if I had it." Often not — symptoms are mild or absent in women, and most men have nothing.

"My partner doesn't have symptoms, so we're fine." Men are usually asymptomatic carriers. They still need treatment.

"It'll go away on its own." No — without treatment, it persists for months or years.

"I can use OTC products." No effective OTC treatment exists. Prescription oral medication is required.

"It's not a real STI." It absolutely is — and an under-discussed one.

"It's just BV with extra symptoms." No — different cause, different treatment.

When to see a clinician

• New itching, abnormal discharge, painful urination, or pain during sex
• Persistent BV-like symptoms that don't respond to BV treatment
• Symptoms after a possible exposure
• Pregnancy with any STI symptoms
• Annual screening if you have risk factors

What to ask

"Can you specifically test me for trichomoniasis? It's not in the basic panel."

"If I'm positive, will both my partner and I get treated together?"

"Should I avoid alcohol during treatment, and for how long after?"

"When should I retest?"

Bottom line

Trichomoniasis is:

• The most common curable STI in the US
• Most often missed because it's not in routine panels
• Usually asymptomatic in men — they're silent reservoirs
• Curable with single-dose or 7-day metronidazole/tinidazole
• Requires partner treatment to prevent reinfection
• Worth specifically requesting if you have symptoms and your basic STI panel is negative

If you've been treated for "BV" multiple times without resolution, or your basic STI panel keeps coming back negative despite real symptoms — ask about trichomoniasis. It's the answer more often than people realize.

For more, see BV vs yeast vs STI, genital itching causes, Mycoplasma genitalium, and free STI testing.