Summary

Trichomoniasis ("Trich") is the most common curable sexually transmitted infection (STI) worldwide, caused by the flagellated protozoan parasite Trichomonas vaginalis. It affects approximately 156 million new cases per year globally (WHO). The infection primarily involves the urogenital tract (Vagina, urethra, paraurethral glands) and is transmitted through unprotected sexual intercourse. Women are more commonly symptomatic (50-70%) presenting with frothy, yellow-green, malodorous vaginal discharge, vulval irritation, and dysuria. Men are often asymptomatic carriers. The pathognomonic sign is "strawberry cervix" (colpitis macularis) – punctate red hemorrhages on the cervix. Diagnosis is by NAAT (Gold standard) or wet mount microscopy showing motile flagellated protozoa. Treatment is with metronidazole (400mg BD for 5-7 days or 2g stat). Partner notification and simultaneous treatment are essential. Complications include increased HIV acquisition/transmission risk and adverse pregnancy outcomes (Preterm birth, Low birth weight). Trichomoniasis frequently co-exists with other STIs (Chlamydia, Gonorrhoea) – always screen for co-infections. [1,2,3]

Key Facts

Clinical Pearls

"Most Common Curable STI Worldwide": 156 million cases/year. Often underdiagnosed compared to Chlamydia.

"Protozoan, NOT Bacteria": Trichomonas is a flagellated protozoan. It does not respond to penicillin or doxycycline. It needs nitroimidazoles.

"Strawberry Cervix": Pathognomonic sign, But only seen in ~2% with naked eye. Requires colposcopy to see in 50%.

"Frothy, Fishy, Yellow-Green": The classic triad description for exams. If you hear "Frothy", think Trich.

"Men Carry, Women Suffer": Men are often asymptomatic reservoirs who reinfect their treated female partners.

"Metronidazole is Curative": 400mg BD for 5-7 days is the Gold Standard. Single 2g dose is an alternative but has higher failure rates in women.

"No Alcohol Rule": Disulfiram-like (Antabuse) reaction is severe. Counsel every patient to avoid alcohol for 48 hours.

"Partner Treatment Essential": You treat the couple, not the individual. Without partner treatment, reinfection is inevitable.

"Screen for Co-infections": You are never "just" treating Trichomonas. Always check for Chlamydia, Gonorrhoea, Syphilis, and HIV.

"HIV Link": Trichomonas increases HIV acquisition by 1.5-2x due to recruitment of inflammatory cells (CD4 targets) to the mucosa.

"Pregnancy Matters": Associated with preterm labour and low birth weight. Symptomatic pregnant women must be treated.

"NAAT is Gold Standard": Sensitivity >95%. Wet mount is good for immediate diagnosis but misses 40% of cases.

"pH is HIGH": Vaginal pH is almost always >4.5 (usually 5.0-6.0). If pH is normal (Less than 4.5), Trich is unlikely (think Candida).

Diagnostic Criteria Summary

Why This Matters Clinically

Trichomoniasis is more than just a nuisance infection.

1. Public Health: It is a major driver of the HIV epidemic, facilitating transmission.
2. Reproductive Health: It causes adverse pregnancy outcomes (preterm birth) and pelvic inflammatory disease (PID).
3. Quality of Life: The symptoms can be distressing and debilitating for women.
4. Clinical Skills: Identifying it requires specific skills (microscopy, specific history questions) and excellent communication for partner notification.
5. Antibiotic Stewardship: Using the right drug (metronidazole) at the right dose prevents resistance.

Historical Context

First described by Alfred Donné in 1836, who observed "animalcules" in purulent discharge. It was long considered a harmless commensal until the mid-20th century when its pathogenicity was confirmed. The introduction of metronidazole in 1960 revolutionised treatment, transforming it from a chronic affliction to a curable condition.

Trichomoniasis is the most common curable STI globally but is frequently underdiagnosed, Especially in asymptomatic men who act as reservoirs. It has significant public health implications due to its association with increased HIV transmission (Inflammation facilitates viral entry), Adverse pregnancy outcomes, And high rates of co-infection with other STIs. Effective management requires treatment of both the index patient AND sexual partners to break the transmission cycle. This condition is commonly examined in OSCE stations focusing on STI history, Discharge assessment, And counselling around alcohol avoidance with metronidazole.

Key Principle

[!NOTE] Detailed examination is crucial not just for diagnosis, but for assessing complications (like PID) and co-infections (like Herpes or Syphilis).
Always examine:
> 1. Abdomen (Tenderness) > 2. External Genitalia (Ulcers, Dermatitis) > 3. Speculum (Discharge, Cervicitis) > 4. Bimanual (Tenderness - PID check)

Examination Protocol: Women

1. Abdominal Examination:

• Palpate lower abdomen.
• Tenderness in iliac fossae suggests Pelvic Inflammatory Disease (PID) or other pathology.

2. External Genital Inspection:

• Vulvitis: Look for erythema and oedema of the labia and introitus.
• Dermatitis: Excoriations from scratching (itch).
• Discharge: May be visible at the introitus (yellow/green).
• Other STIs: Check for Herpes ulcers, Syphilis chancres, Warts.

3. Speculum Examination (Crucial Step):

• Discharge: Look for pooling in the posterior fornix.
  • Classic: Frothy, Yellow-green, Bubbles visible.
  • Note: Mucopurulent discharge from the OS suggests Gonorrhoea/Chlamydia.
• Vaginal Walls: Erythematous, "Angry" appearance.
• Cervix:
  • "Strawberry Cervix" (Colpitis Macularis): Punctate petechial hemorrhages.
  • Friability: Bleeds easily on contact (swabbing).
• pH Testing: Touch indicator paper to lateral vaginal wall.

4. Bimanual Examination:

• Goal: Exclude PID / Upper Genital Tract Infection.
• Cervical Motion Tenderness (CMT): "Chandelier sign" - pain on moving cervix.
• Adnexal Tenderness: Pain in ovarian regions.
• Uterine Tenderness: Pain on compressing uterus.
• If any of these are positive, treat for PID immediately.

Examination Protocol: Men

1. Inspection:

• Urethral Meatus: Check for discharge (may need to "milk" the urethra).
• Glans/Prepuce: Check for Balanitis (inflammation), Ulcers, Warts.

2. Palpation:

• Testicles: Check for tenderness/swelling (Epididymo-orchitis).
• Epididymis: Tenderness suggests ascending infection.

3. Digital Rectal Exam (DRE):

• Only if prostatitis suspected (Perineal pain, dysuria +++).
• Boggy, tender prostate.

Documentation Checklist (Medico-legal)

"Use of the Speculum" - Clinical Tips

[!TIP] Optimising the Exam: > 1. Warm the speculum: Cold metal causes muscle spasm. > 2. Lubrication: Use water or minimal water-soluble lube (excess lube can interfere with slides/swabs). > 3. Angle: Insert at 45 degrees, then rotate to horizontal. > 4. Visualize: Ensure you can see the cervix fully to rule out "Strawberry" spots. > 5. Swab Order:

• 1st: Charcoal Swab (Bacteria/Candida) - If needed
• 2nd: NAAT (DNA) - Or first if sole test
• 3rd: pH/Wet Mount - Last

Strawberry Cervix - Detailed

Vaginal pH Interpretation Guide

Treatment Efficacy

Prognostic Factors

Good Prognosis Indicators:

• Adherence to 7-day course.
• Partner simultaneously treated.
• Sexual abstinence during treatment.
• No co-infections.

Poor Prognosis Indicators:

• Co-infection (Bacterial Vaginosis).
• Untreated partner (Reinfection is #1 cause of "failure").
• HIV infection (May require longer course).
• Non-adherence (Alcohol use, Nausea).

Reinfection vs Resistance

Reinfection (Common):

• Occurs in ~17% of women within 3 months.
• Usually due to resumption of sex with untreated partner.
• Management: Retreatment + Strict partner notification.

Resistance (Rare):

• Occurs in Less than 5% of cases.
• Mechanism: Altered metabolic pathways (reduced nitroreductase activity in hydrogenosome).
• Classification:
  • Low-level: Responds to higher dose Metronidazole.
  • High-level: Requires Tinidazole or specialist regimens.

Long-Term Sequelae

• No protective immunity: Patients can get Trichomoniasis multiple times.
• No chronic carrier state (after cure): Once cured, the parasite is gone.
• Fertility: Usually preserved if no PID.

Key Guidelines Summary

Landmark Trials & Evidence

1. Seven-Day vs Single-Dose Metronidazole (Kissinger et al., 2018)

• Study Type: Multicentre, open-label, RCT.
• Population: Women with Trichomoniasis (n=623).
• Intervention: Metronidazole 500mg BD x 7 days vs 2g Single Dose.
• Outcome: Treatment failure at 4 weeks.
• Results:
  • 7-day Group Failure: 10.6%
  • Single Dose Group Failure: 19.7%
  • Relative Risk: Single dose failure risk RR = 1.87.
• Conclusion: 7-day course is significantly superior.
• Clinical Impact: Changed CDC and BASHH guidelines to prefer 7-day course for women.
• PMID: 30281989 (Link)

2. Treating Trichomoniasis in HIV (Kissinger et al., 2015)

• Study Type: RCT.
• Result: Treating T. vaginalis in HIV-positive women reduces genital HIV RNA shedding.
• Implication: Treatment functions as "Treatment as Prevention" for HIV.
• PMID: 26242185

3. Preterm Birth and Metronidazole (Klebanoff et al., 2001)

• Study Type: Large RCT.
• Finding: Treating asymptomatic Trichomoniasis in pregnancy did NOT reduce preterm birth (and might have slightly increased it in some subgroups).
• Nuance: This refers to asymptomatic screening. Symptomatic women must always be treated.
• PMID: 11516431

4. Partner Treatment Efficacy (Seña et al., 2007)

• Finding: Partner notification and treatment reduces recurrence rates by >75%.
• Implication: Treat the partner or the patient will return.

5. NAAT vs Culture vs Wet Mount (Hobbs et al., 2013)

• Study: Comparison of diagnostic methods.
• Sensitivity Data:
  • Wet Mount: 51%
  • Culture: 75%
  • Aptima TV (NAAT): 98%
• Conclusion: Microscopy misses half of all cases. NAAT is essential.
• PMID: 23392437

Guideline Discordance Areas

Evolving Evidence: Resistance

• Prevalence: Currently low (Less than 5%) but rising.
• Mechanism: Downregulation of biological activation of metronidazole.
• Testing: Only at specialist centres (e.g., CDC, reference labs).
• New Drugs: Secnidazole (single dose 2g) FDA approved (2017) – similar to metronidazole but longer half-life.

What is Trichomoniasis?

Trichomoniasis (or "Trich") is a very common sexually transmitted infection (STI). It is caused by a tiny parasite (not a bacteria or virus).

• It is very common: Millions of people get it every year.
• It is easily treated: Antibiotics usually cure it completely.
• It is not dangerous (mostly): But it can cause problems in pregnancy if untreated.

Signs and Symptoms

In Women: Most women (about 7 in 10) have symptoms:

• Discharge: It might be yellow or green, frothy, and have a strong, fishy smell.
• Itching: Soreness or severe itching around the vagina.
• Pain: Discomfort when passing urine or during sex.

In Men: Most men (9 in 10) have NO symptoms. They carry the parasite without knowing.

• Occasionally: Mild discharge or irritation inside the penis.
• Risk: Because they feel fine, they pass it on unknowingly.

How is it Treated?

The treatment is an antibiotic called Metronidazole.

• usually taken twice a day for 7 days.
• Sometimes given as a single large dose.

⚠️ IMPORTANT: The "No Alcohol" Rule

You MUST NOT drink any alcohol while taking these tablets, and for 48 hours (2 days) after finishing the course.

Partner Notification: The Hard Part

You must tell your sexual partner(s). Even if they feel 100% fine.

• If they are not treated, they will pass it straight back to you.
• Then you will need to take the antibiotics again!

How to say it:

"I've just been diagnosed with an infection called Trichomoniasis. It's easily treated with tablets, but you need to get treated too, even if you have no symptoms. Please go to a clinic this week."

Myth Buster

Frequently Asked Questions (FAQs)

Q: Will it affect my fertility? A: Generally no. Unlike Chlamydia or Gonorrhoea, it rarely damages the tubes. However, treating it creates a healthier environment for conception.

Q: Can I have sex during treatment? A: No. You should wait until you AND your partner have finished the tablets, plus 7 days. This allows the medication to work and ensures you don't pass it back and forth.

Q: I'm pregnant. Is the baby safe? A: Untreated trichomoniasis is linked to having the baby too early (preterm birth). Treating it reduces the infection, although the link to outcomes is complex. The antibiotic metronidazole is generally considered safe in pregnancy.

Q: How did I get it? I haven't had sex in months. A: In some cases, the infection can be present for months or even years without causing major symptoms, then suddenly "flare up." So it doesn't always prove a partner has cheated recently.

When to Seek Help Urgently

Go back to your doctor if:

• You vomit the tablets up (you might need a re-dose).
• Symptoms don't go away after the course.
• You develop severe lower tummy pain or fever (could be a deeper infection).

High-Yield Facts for Exams

"Buzzword Bingo"

Common Exam Questions

Question 1 (SBA): A 24-year-old woman presents with offensive vaginal discharge. Speculum examination reveals a "strawberry cervix" with punctate hemorrhages. The vaginal pH is 5.5. What is the most likely causative organism? A. Candida albicans B. Gardnerella vaginalis C. Trichomonas vaginalis D. Neisseria gonorrhoeae E. Chlamydia trachomatis Answer: C (Pathognomonic sign + pH >4.5)

Question 2 (SBA): A 30-year-old woman is prescribed metronidazole for trichomoniasis. What specific advice must be given regarding alcohol consumption? A. Avoid alcohol for 1 hour after taking B. Alcohol decreases the efficacy of the drug C. Avoid alcohol during treatment and for 48 hours after D. Alcohol causes sedation with this drug E. No specific advice needed Answer: C (Disulfiram-like reaction: Flushing, Vomiting)

Question 3 (SBA): Which of the following complications is most strongly associated with untreated trichomoniasis in pregnancy? A. Congenital malformations B. Preterm delivery and low birth weight C. Neonatal conjunctivitis D. Neonatal pneumonia E. Hydrops fetalis Answer: B (Preterm delivery risk increased 1.4-1.8x)

OSCE Station: STI Counselling

Scenario: "Sarah, 23, has just been diagnosed with Trichomoniasis via a swab taken 3 days ago. She is currently asymptomatic. Please explain the diagnosis, management plan, and partner notification requirements."

Mark Scheme:

Viva Points

Candidate Opening Statement:

"Trichomoniasis is a sexually transmitted infection caused by the flagellated protozoan Trichomonas vaginalis. It has a global incidence of over 150 million cases annually. Clinically, it presents with vulvitis and a characteristic frothy yellow-green discharge, though men are often asymptomatic reservoirs. Management involves 7 days of metronidazole, strict alcohol avoidance, and simultaneous partner treatment to prevent reinfection."

Examiner: "Why is the 7-day course preferred over the single dose?"

Candidate: "Meta-analyses (Cochrane) show the 7-day course has significantly higher cure rates (>95% vs ~85%) and lower reinfection rates compared to the 2g single dose. It is the recommended first-line treatment in UK (BASHH) and US (CDC) guidelines."

Examiner: "What is the mechanism of the alcohol reaction?"

Candidate: "Metronidazole inhibits the enzyme aldehyde dehydrogenase. This causes an accumulation of acetaldehyde when alcohol is consumed, leading to the 'disulfiram-like' reaction of flushing, tachycardia, nausea, and vomiting."

Common Mistakes to Avoid

Clinical Reasoning Scenarios

Scenario A: Recurrent Symptoms

• Situation: Patient treated 3 weeks ago returns with same symptoms.
• Reasoning:
  1. Adherence: Did she take the pills? (And avoid alcohol/vomiting?)
  2. Reinfection: Did partner get treated? Did they have sex too soon? (Most common)
  3. Resistance: Rare, but possible.
• Action: Retreatment (often higher dose) + STRICT partner management.

Scenario B: Pregnancy

• Situation: 10 weeks pregnant, symptomatic.
• Reasoning: Metronidazole generally safe, but avoid high stat doses in 1st trimester.
• Action: Treat with standard 5-7 day course. Symptomatic relief outweighs theoretical risks.

Dangerous Errors (Automatic Fail)

[!CAUTION] OSCE Fail Points: > 1. Failing to warn about Alcohol interaction (Patient safety). > 2. Failing to address Partner notification (Public health). > 3. Dismissing symptoms in Pregnancy (Fetal risk).

Last Reviewed: 2025-12-25 | MedVellum Editorial Team

Medical Disclaimer: MedVellum content is for educational purposes and clinical reference. Clinical decisions should account for individual patient circumstances. Always consult appropriate specialists and current guidelines.