Trichomoniasis

1. Clinical Overview

Summary

Trichomoniasis ("Trich") is the most common curable sexually transmitted infection (STI) worldwide, caused by the flagellated protozoan parasite Trichomonas vaginalis. Global burden is estimated at approximately 156 million new cases annually, with a prevalence of 5.3% in women aged 15-49 years globally. [1] 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 (70-90% asymptomatic), serving as reservoirs for transmission. [2] The pathognomonic sign is "strawberry cervix" (colpitis macularis) – punctate red hemorrhages on the cervix visible in 2% with naked eye examination but up to 50% with colposcopy. [3] Diagnosis is by NAAT (nucleic acid amplification testing - gold standard with sensitivity > 95%) or wet mount microscopy showing motile flagellated protozoa (sensitivity only 50-60%). [4] Treatment is with metronidazole 400mg BD for 5-7 days (cure rate > 95%) or 2g stat dose (cure rate 85-90%). [5] Partner notification and simultaneous treatment are essential to prevent reinfection, which occurs in 17% of women within 3 months. [6] Complications include increased HIV acquisition risk (relative risk 1.5-2.7) [7], increased HIV transmission in co-infected individuals [8], and adverse pregnancy outcomes including preterm delivery (adjusted OR 1.4) and low birth weight. [9] Trichomoniasis frequently co-exists with other STIs (10-20% with Chlamydia, 10-15% with Gonorrhoea, 30-50% with bacterial vaginosis) – full STI screening is mandatory. [10,11]

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.

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2. Epidemiology

Key Principle

[!NOTE] Trichomoniasis is the most common curable STI worldwide with ~156 million new cases/year. It is underdiagnosed because many cases (Especially in men) are asymptomatic. It has significant public health implications for HIV transmission and pregnancy outcomes.

Incidence & Prevalence

Global Burden by Region

Demographics - Detailed

Healthcare Utilisation Impact

Risk Factors - Detailed

High-Risk Groups:

Predisposing Factors:

Co-infections - Detailed

Public Health Implications

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3. Pathophysiology

Key Principle

[!NOTE] Trichomonas vaginalis is an extracellular, flagellated protozoan parasite. It is an obligate parasite (cannot survive long outside the host). Pathogenesis involves adhesion to the cervicovaginal epithelium, cytotoxicity, and a robust inflammatory response (neutrophil influx) which characterises the clinical discharge and facilitates HIV transmission.

Organism Characteristics - Detailed

Virulence Factors

Pathophysiology Steps - Detailed

Step 1: Transmission and Colonisation

• Entry via sexual intercourse (inoculum).
• Flagella aid movement through vaginal mucus.
• pH Preference: Thrives in higher pH (5.0-6.0). Normal vaginal acidity (Less than 4.5) is protective.
• Menstrual blood (pH 7.4) facilitates establishment (hence symptoms often post-menses).

Step 2: Adhesion (Contact-Dependent)

• Parasite transforms from free-swimming to amoeboid form upon contact.
• Adhesins bind to laminin and fibronectin on host epithelium.
• This "kiss of death" contact is required for cytotoxicity.

Step 3: Cytotoxicity and Epithelial Damage

• Micropinocytosis: Parasite rarely ingests host cells but "nibbles" them.
• Release of perforin-like proteins and proteases.
• Induction of host cell apoptosis and necrosis.
• Disruption of epithelial barrier integrity.

Step 4: The Inflammatory Response (The "Purulent" Phase)

• Host epithelial cells release chemokines (IL-8).
• Massive influx of Neutrophils (PMNs) into the vaginal lumen.
• Discharge: The frothy, yellow-green discharge is largely composed of neutrophils and dead epithelial cells.
• Free Radical Release: Neutrophils release ROS, causing further tissue irritation.

Step 5: Impact on Vaginal Microbiome

• T. vaginalis correlates with loss of healthy Lactobacillus.
• Synergistic relationship with BV-associated bacteria (Gardnerella, Mycoplasma).
• Both thrive in anaerobic, high pH environment.
• The high pH neutralises the protective effect of lactic acid.

Step 6: "Strawberry Cervix" Formation

• Colpitis Macularis: Local dilation of capillaries and punctate hemorrhages.
• Caused by high local concentration of organisms and inflammatory mediators.
• Gives the mottled red appearance.

Immune Evasion Mechanisms

The HIV Connection (Crucial Mechanism)

Trichomoniasis increases HIV transmission risk by 2-fold via:

1. Epithelial Breach: Micro-ulcerations provide entry portal for virus.
2. Target Cell Recruitment: Inflammation recruits CD4+ T-cells and Macrophages (HIV targets) to the genital tract.
3. Viral Shedding: Increase HIV RNA shedding in co-infected individuals.
4. Flora Disruption: Loss of protective H2O2-producing lactobacilli.

Pathophysiology Diagram

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Pathophysiology Diagram

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4. Clinical Presentation

Key Principle

[!NOTE] Trichomoniasis Presentation:

• Women: 50-70% symptomatic. Classic triad: Frothy yellow-green discharge, Vulval irritation, Dysuria.
• Men: 70-90% asymptomatic. Key reservoir for transmission.
• Pathognomonic: Strawberry cervix (Colpitis macularis) - Specific but insensitive.

Incubation and Course

Presentation by Sex - Detailed

Women (Symptomatic in 50-70%):

Men (Asymptomatic in 70-90%):

Differential Diagnosis - Vaginal Discharge

Red Flags requiring Urgent/Specialist Assessment

[!CAUTION] Safeguarding Alert: Diagnosis of Trichomonas vaginalis in a child is a definitive marker of sexual abuse until proven otherwise, as it is not commensal and does not survive in the environment.

Assessment of Complications (Algorithm)

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5. Clinical Examination

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

Strawberry Cervix - Detailed

Vaginal pH Interpretation Guide

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6. Investigations

Key Principle

[!IMPORTANT] Diagnostic Approach:

1. NAAT (Nucleic Acid Amplification Test) is the Gold Standard (Sensitivity > 95%).
2. Wet Mount Microscopy provides immediate point-of-care diagnosis but has low sensitivity (50-60%) - A negative result does NOT exclude Trichomoniasis.
3. Vaginal pH > 4.5 supports the diagnosis (but is non-specific).

Diagnostic Tests Comparison

NAAT Testing Strategy (Gold Standard)

Sample Sites:

Protocol:

• Often included in "Triple Screen" panels (Chlamydia + Gonorrhoea + Trichomonas).
• Can use same swab technology as for CT/NG (e.g. Aptima).
• Window Period: Can detect reliable DNA 4-7 days after exposure.

Wet Mount Microscopy (Point-of-Care)

Procedure:

1. Take High Vaginal Swab (HVS) from posterior fornix.
2. Place directly into tube of normal saline (0.9%).
3. Place drop on slide with cover slip.
4. Examine immediately (within 10-15 mins) under phase-contrast (x400).

Findings:

• Trichomonads: Pear-shaped, slightly larger than WBCs.
• Motility: Characteristic jerky / twitching / tumbling motion.
• WBCs: Usually abundant (> 10 per HPF).
• Clue Cells: May be present (Concurrent BV).

[!WARNING] Negative Microscopy: If wet mount is negative but symptoms persist or suspicion is high, you MUST send a NAAT. Do not rely solely on microscopy.

Vaginal pH Testing

Procedure:

• Touch pH paper to vaginal wall (mid-vagina).
• Avoid cervical mucus (pH 7.0) or lubricant.

Interpretation:

• Normal: pH Less than 4.5
• Trichomoniasis: pH > 4.5 (Often 5.0-6.0)
• Bacterial Vaginosis: pH > 4.5
• Candida: pH Less than 4.5 (Normal)

Additional Investigations and Screening

Full STI Screen (Recommended for all):

Speculum Examination Checklist:

1. Inspect Vulva: Dermatitis, discharge.
2. Insert Speculum: Note discharge characteristics.
3. Inspect Cervix: Look for "Strawberry" signs (Colpitis macularis).
4. Take Swabs: HVS (pH/Wet mount) + NAAT.
5. Bimanual: Check for tenderness (PID).

Why Culture is Rarely Used Now

• InPouch TV System was historic gold standard.
• Requires incubation for up to 7 days.
• Lower sensitivity than modern NAAT.
• Now primarily used for Resistance Testing (sending isolates to reference labs).

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7. Management

Key Principle

[!IMPORTANT] Metronidazole is curative (More than 90% cure rate) Partner notification and treatment essential Avoid alcohol during treatment (Disulfiram reaction)

Management Algorithm

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First-Line Treatment - Detailed

7-Day vs Single Dose Comparison:

Second-Line Treatment - Detailed

Metronidazole Pharmacokinetics & Interactions

Key Drug Interactions:

Prescribing in Special Populations (Detailed)

1. Pregnancy:

• First Trimester: Metronidazole 400mg BD for 7 days is safe. Avoid high-dose stat regimens if possible (theoretical risk, though evidence supports safety).
• Second/Third Trimester: Metronidazole 400mg BD for 7 days.
• Preterm Risk: Symptomatic infection must be treated to reduce preterm birth risk.
• Asymptomatic Screening: Not routinely recommended.

2. Breastfeeding:

• Metronidazole is excreted in breast milk.
• Standard Advice: Safe to use. Large doses (2g stat) may cause bitter taste in milk.
• Strategy: Can withhold breastfeeding for 12-24 hours after 2g stat dose if concerned, or use 400mg BD regimen (levels lower).
• British National Formulary (BNF): "Amount too small to be harmful."

3. Renal Impairment:

• CKD 1-3 (eGFR > 30): No dose adjustment needed.
• CKD 4-5 (eGFR Less than 30): No dose adjustment usually needed for short course, but monitor for metabolites.
• Dialysis: Metronidazole is removed by dialysis. Administer dose after dialysis session.

4. Hepatic Impairment:

• Mild/Moderate: No adjustment.
• Severe (Child-Pugh C): Reduce dose by 50% or increase interval (e.g. 400mg OD), as metabolism is slowed.

5. Metronidazole Allergy:

• True allergy (anaphylaxis) is rare but challenging.
• Alternatives:
  • Tinidazole: Often cross-reactivity exists (contraindicated).
  • Desensitisation: Oral desensitisation protocols available in specialist centres.
  • Non-Nitroimidazole agents: Paromomycin (intravaginal) or high-dose Clotrimazole have very low cure rates (Less than 50%) and are not recommended unless absolute necessity.
  • Referral: All true allergy cases require GUM Specialist management.

Metronidazole Counselling - Detailed

Essential Counselling Points:

Sample Counselling Script (OSCE):

"I'm prescribing you an antibiotic called Metronidazole. You'll take one tablet twice a day for 7 days. It's very important that you take all the tablets, Even if you feel better. There's one very important thing – You must NOT drink any alcohol while taking these tablets, And for 48 hours after finishing. If you do, You'll become very unwell with severe vomiting, Flushing, And headaches. Common side effects include nausea and a metallic taste, Which are normal. Your partner must be treated at the same time, Even if they have no symptoms. You should both avoid sex until 7 days after you've both finished treatment. Does that all make sense? Any questions?"

Partner Notification - Detailed

Partner Notification Counselling:

Test of Cure

Management of Treatment Failure (Step-by-Step)

If symptoms persist or test remains positive:

Step 1: Check Compliance & Sexual History (The Basics)

• Adherence: Did they take the pills? (Did they vomit?)
• Timing: Did they complete the course?
• Alcohol: Did they stop alcohol (avoiding vodka-vomiting)?
• Re-exposure: Did they have sex? Was partner treated? (Most common cause)

Step 2: Reinfection vs Relapse

• Reinfection: Most likely (> 90%). New exposure or untreated partner.
  • Action: Retreat with standard course (Metronidazole 400mg BD x 7 days).
  • Partner: Ensure partner is treated (Supervised therapy if needed).
• Relapse: Persistence despite adherence and no re-exposure.
  • Action: Suspect resistance or poor absorption.

Step 3: Empiric Second-Line (If compliance confirmed)

• Regimen: Metronidazole 400mg TDS for 7 days (UK) or Tinidazole 2g single dose.
• Alternative: Tinidazole 500mg QDS for 1 week (High dose).
• Note: High dose metronidazole/tinidazole has more side effects (nausea, neurotoxicity).

Step 4: Refractory / Resistant Cases

• Definition: Failure of nitroimidazole treatment after excluding reinfection/non-compliance.
• Action:
  1. Culture: Swab for Culture and Sensitivity (Reference Lab).
  2. Specialist Management: Referral to GUM consultant.
  3. High Dose Tinidazole: 1g BD or TDS for 14 days (Specialist only).
  4. FemCure Trial Regimens: Dequalinium Chloride (10mg PV OD x 6 days) – Shows promise.
  5. Paromomycin: Intravaginal cream (Poor efficacy, side effects).
  6. Boric Acid: Low cure rate, salvage only.

[!WARNING] Metronidazole Resistance:

• Rare (Less than 5%) but increasing worldwide.
• Mechanisms involve reduced nitroreductase activity in the hydrogenosome.
• Do not keep repeating the same failing dose. Escalate to specialist.

Alternative / Natural Remedies (Facts and Myths)

Patients frequently ask about non-antibiotic treatments. It is important to be clear:

[!TIP] Counselling Tip: "This is a parasite that 'swims'. Flushing it with water or using herbal remedies won't kill it. You need the specific antibiotic that stops its engine (hydrogenosome) working."

Follow-Up Strategy

OSCE Station: Trichomoniasis Counselling

Expected Competencies:

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8. Complications

Overview

Pregnancy Complications - Detailed Mechanisms

Preterm Birth and Low Birth Weight:

• Risk: 1.4-1.8x increased risk of preterm delivery (Less than 37 weeks).
• Mechanism:
  1. T. vaginalis produces proteases that degrade the chorioamniotic membrane.
  2. Induces local inflammation (IL-8, Prostaglandins).
  3. Prostaglandins trigger uterine contractions.
  4. Weakening of membranes leads to PROM (Premature Rupture of Membranes).

Implication for Management:

• Symptomatic pregnant women MUST be treated.
• Screening asymptomatic pregnant women is controversial (some studies suggested treatment might increase PTB, but recent guidelines suggest treating).

The HIV Synergy (Public Health Critical)

1. Increased Acquisition (Getting HIV):

• T. vaginalis causes microscopic ulcerations in the epithelium.
• It recruits CD4+ T-cells (HIV targets) to the vaginal/cervical mucosa.
• Result: An HIV-negative person with Trichomoniasis is 1.5-2 times more likely to acquire HIV if exposed.

2. Increased Transmission (Passing HIV):

• In HIV-positive individuals, Trichomoniasis increases genital viral shedding.
• Result: An HIV-positive person with Trichomoniasis is more infectious to their partners.

[!IMPORTANT] Conclusion: Effective control of Trichomoniasis is a crucial HIV prevention strategy.

Pelvic Inflammatory Disease (PID)

• T. vaginalis is an independent risk factor for PID.
• Can transport bacteria into the upper genital tract ("Trojan Horse" effect).
• Presentation: Pelvic pain, deep dyspareunia.
• Management: If PID suspected, treat for PID (covering GC/CT/Anaerobes) + add Metronidazole for TV.

Male Complications (Under-recognised)

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9. Prognosis & Outcomes

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.

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10. Evidence & Guidelines

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.

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11. Patient/Layperson Explanation

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).

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12. References

Primary Guidelines and Meta-Analyses

1. Rowley J, Vander Hoorn S, Korenromp E, et al. Chlamydia, gonorrhoea, trichomoniasis and syphilis: global prevalence and incidence estimates, 2016. Bull World Health Organ. 2019;97(8):548-562P. DOI: 10.2471/BLT.18.228486 PMID: 31384073

2. Sherrard J, Ison C, Moody J, et al. United Kingdom National Guideline on the Management of Trichomonas vaginalis 2014. Int J STD AIDS. 2014;25(8):541-549. DOI: 10.1177/0956462414525947 PMID: 24616115

3. Wolner-Hanssen P, Krieger JN, Stevens CE, et al. Clinical manifestations of vaginal trichomoniasis. JAMA. 1989;261(4):571-576. DOI: 10.1001/jama.1989.03420040111028 PMID: 2783346

4. Schwebke JR, Gaydos CA, Davis T, et al. Clinical evaluation of the Cepheid Xpert TV assay for detection of Trichomonas vaginalis with prospectively collected specimens from men and women. J Clin Microbiol. 2018;56(2):e01091-17. DOI: 10.1128/JCM.01091-17 PMID: 29167291

5. Kissinger P, Muzny CA, Mena LA, et al. Single-dose versus 7-day-dose metronidazole for the treatment of trichomoniasis in women: an open-label, randomised controlled trial. Lancet Infect Dis. 2018;18(11):1251-1259. DOI: 10.1016/S1473-3099(18)30423-7 PMID: 30281989

6. Peterman TA, Tian LH, Metcalf CA, et al. High incidence of new sexually transmitted infections in the year following a sexually transmitted infection: a case for rescreening. Ann Intern Med. 2006;145(8):564-572. DOI: 10.7326/0003-4819-145-8-200610170-00005 PMID: 17043338

7. Masha SC, Wahome E, Vaneechoutte M, et al. High prevalence of curable sexually transmitted infections among pregnant women in a rural county hospital in Kilifi, Kenya. PLoS One. 2017;12(3):e0175166. DOI: 10.1371/journal.pone.0175166 PMID: 28358820

8. Van Der Pol B, Kwok C, Pierre-Louis B, et al. Trichomonas vaginalis infection and human immunodeficiency virus acquisition in African women. J Infect Dis. 2008;197(4):548-554. DOI: 10.1086/526496 PMID: 18275275

9. Silver BJ, Guy RJ, Kaldor JM, Jamil MS, Rumbold AR. Trichomonas vaginalis as a cause of perinatal morbidity: a systematic review and meta-analysis. Sex Transm Dis. 2014;41(6):369-376. DOI: 10.1097/OLQ.0000000000000134 PMID: 24825333

10. Bradshaw CS, Tabrizi SN, Read TR, et al. Etiologies of nongonococcal urethritis: bacteria, viruses, and the association with orogenital exposure. J Infect Dis. 2006;193(3):336-345. DOI: 10.1086/499434 PMID: 16388480

Treatment and Drug Resistance

11. Workowski KA, Bachmann LH, Chan PA, et al. Sexually Transmitted Infections Treatment Guidelines, 2021. MMWR Recomm Rep. 2021;70(4):1-187. DOI: 10.15585/mmwr.rr7004a1 PMID: 34292926

12. Kirkcaldy RD, Augostini P, Asbel LE, et al. Trichomonas vaginalis antimicrobial drug resistance in 6 US cities, STD Surveillance Network, 2009-2010. Emerg Infect Dis. 2012;18(6):939-943. DOI: 10.3201/eid1806.111590 PMID: 22607745

13. Schwebke JR, Barrientes FJ. Prevalence of Trichomonas vaginalis isolates with resistance to metronidazole and tinidazole. Antimicrob Agents Chemother. 2006;50(12):4209-4210. DOI: 10.1128/AAC.00814-06 PMID: 17000740

Pathophysiology and Virulence

14. Hirt RP. Trichomonas vaginalis virulence factors: an integrative overview. Sex Transm Infect. 2013;89(6):439-443. DOI: 10.1136/sextrans-2013-051105 PMID: 23605850

15. Fichorova RN, Buck OR, Yamamoto HS, et al. The villain team-up or how Trichomonas vaginalis and bacterial vaginosis alter innate immunity in concert. Sex Transm Infect. 2013;89(6):460-466. DOI: 10.1136/sextrans-2013-051052 PMID: 23903808

Diagnostics and Screening

16. Hobbs MM, Seña AC. Modern diagnosis of Trichomonas vaginalis infection. Sex Transm Infect. 2013;89(6):434-438. DOI: 10.1136/sextrans-2013-051057 PMID: 23633669

17. Van Der Pol B, Williams JA, Taylor SN, et al. Detection of Trichomonas vaginalis DNA by use of self-obtained vaginal swabs with the BD ProbeTec Qx assay on the BD Viper system. J Clin Microbiol. 2014;52(3):885-889. DOI: 10.1128/JCM.03104-13 PMID: 24391199

HIV and Complications

18. McClelland RS, Sangare L, Hassan WM, et al. Infection with Trichomonas vaginalis increases the risk of HIV-1 acquisition. J Infect Dis. 2007;195(5):698-702. DOI: 10.1086/511278 PMID: 17262712

19. Kissinger P, Amedee A, Clark RA, et al. Trichomonas vaginalis treatment reduces vaginal HIV-1 shedding. Sex Transm Dis. 2009;36(1):11-16. DOI: 10.1097/OLQ.0b013e318186decf PMID: 19008776

Pregnancy Outcomes

20. Cotch MF, Pastorek JG 2nd, Nugent RP, et al. Trichomonas vaginalis associated with low birth weight and preterm delivery. The Vaginal Infections and Prematurity Study Group. Sex Transm Dis. 1997;24(6):353-360. DOI: 10.1097/00007435-199707000-00008 PMID: 9243743

21. Klebanoff MA, Carey JC, Hauth JC, et al. Failure of metronidazole to prevent preterm delivery among pregnant women with asymptomatic Trichomonas vaginalis infection. N Engl J Med. 2001;345(7):487-493. DOI: 10.1056/NEJMoa003329 PMID: 11519502

Partner Notification and Public Health

22. Schwebke JR, Hobbs MM, Taylor SN, et al. Molecular testing for Trichomonas vaginalis in women: results from a prospective U.S. clinical trial. J Clin Microbiol. 2011;49(12):4106-4111. DOI: 10.1128/JCM.01291-11 PMID: 21998423

Additional Key Reviews

Kissinger P. Trichomonas vaginalis: a review of epidemiologic, clinical and treatment issues. BMC Infect Dis. 2015;15:307. DOI: 10.1186/s12879-015-1055-0 PMID: 26242185

Seña AC, Miller WC, Hobbs MM, et al. Trichomonas vaginalis infection in male sexual partners: implications for diagnosis, treatment, and prevention. Clin Infect Dis. 2007;44(1):13-22. DOI: 10.1086/511144 PMID: 17143809

Schwebke JR, Burgess D. Trichomoniasis. Clin Microbiol Rev. 2004;17(4):794-803. DOI: 10.1128/CMR.17.4.794-803.2004 PMID: 15489349

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Glossary of Terms

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14. Advanced Topics

Molecular Biology and Genome Insights

Recent genomic sequencing of Trichomonas vaginalis has revealed:

Mechanism of Metronidazole Action:

1. Drug enters cell by passive diffusion
2. Nitroreductase enzymes in the hydrogenosome reduce the nitro group
3. Reduction creates toxic intermediates (nitro radicals, nitroso compounds)
4. These damage DNA, proteins, and membranes
5. Selective toxicity: mammalian cells lack anaerobic environment needed for activation [12,13]

Resistance Mechanisms

Types of Metronidazole Resistance:

Resistance Testing:

• Only available at specialized reference laboratories (CDC, PHE)
• Requires culture of organism (difficult, 7-day incubation)
• MIC determination by agar dilution method
• Definitions: Resistance = MIC > 50 μg/mL for metronidazole [12]

Management of Confirmed Resistance:

Step 1: Tinidazole 2g PO daily × 14 days
Step 2: If fails, high-dose therapy with specialist consultation
   - Metronidazole 2-3g PO daily + Tinidazole 2g PO daily × 14 days
   OR
   - Tinidazole 1g BD + Intravaginal paromomycin × 14 days
Step 3: Consider experimental therapies (Dequalinium chloride)

Trichomonas in Men - Underdiagnosed Reservoir

Clinical Manifestations in Men:

Why Men Are Asymptomatic:

1. Anatomical: Urethra is exposed to urine flow (mechanical cleansing)
2. Immunological: Different mucosal immune environment
3. Hormonal: Testosterone may influence susceptibility
4. Organism Load: Lower parasite burden in male urethra [14]

Implications:

• 70-90% of infected men are asymptomatic
• Partners of infected women should be treated empirically without testing
• Single-dose therapy may be acceptable in men (better adherence, lower reinfection if female partner treated) [11]

Trichomoniasis and Cancer Risk

Prostate Cancer Association: Emerging evidence suggests possible link between T. vaginalis and prostate cancer:

• Seroprevalence studies show higher anti-TV antibodies in prostate cancer patients
• Proposed mechanism: Chronic inflammation → oxidative DNA damage
• Current evidence: Observational only, causation not established
• Clinical action: None currently recommended beyond standard screening

Cervical Neoplasia:

• No strong evidence for direct carcinogenesis
• May increase HPV persistence through immune modulation
• Conflicting data on cervical dysplasia progression [15]

Co-Infection Dynamics

Bacterial Vaginosis (BV) Synergy:

T. vaginalis and BV have a bidirectional relationship:

Treatment Implications:

• Metronidazole treats both TV and BV
• Recurrent BV may indicate undiagnosed/untreated TV
• Consider adding lactobacillus replacement therapy post-treatment [15]

HIV Co-Infection:

Pathophysiological mechanisms of TV-HIV interaction:

TV Infection
    ↓
Epithelial Microabrasions
    ↓
↑ Pro-inflammatory Cytokines (IL-8, IL-1β, TNF-α)
    ↓
Recruitment of CD4+ T-cells, Macrophages to Genital Mucosa
    ↓
↑ HIV Target Cells at Site of Exposure
    ↓
INCREASED HIV ACQUISITION RISK (RR 1.5-2.7)

In HIV-positive individuals:

• TV increases genital HIV-1 RNA shedding (↑ viral load in genital secretions)
• Increased HIV transmission to partners
• Treatment of TV reduces HIV shedding [18,19]

Special Populations

1. Immunocompromised Patients:

2. Elderly Patients:

Trichomoniasis in post-menopausal women:

• Often misdiagnosed as atrophic vaginitis
• May have co-existent atrophy (pH > 4.5 in both)
• Strawberry cervix appearance similar to atrophic changes
• Key difference: Motile organisms on wet mount
• Treatment: Standard metronidazole + vaginal estrogen if atrophy confirmed

3. Adolescents:

Special considerations:

• Safeguarding assessment essential (assess for coercion/abuse)
• Fraser competence evaluation (can consent to treatment less than 16 years in UK)
• Partner notification challenging (peer pressures)
• Education about safer sex critical
• Confidentiality paramount

4. Sex Workers:

Novel and Emerging Therapies

1. Dequalinium Chloride:

• Vaginal tablet (10mg) used for 6 consecutive nights
• Mechanism: Disrupts mitochondrial/hydrogenosomal membrane
• Efficacy: Cure rates 70-85% in small studies
• Advantage: No systemic absorption, no alcohol restriction
• Availability: Licensed in some European countries, not FDA-approved
• Use: Salvage therapy for nitroimidazole-resistant cases

2. Secnidazole:

• Single 2g oral dose (FDA approved 2017)
• Nitroimidazole with longer half-life (17 hours vs 8 hours)
• Efficacy: Non-inferior to metronidazole 7-day course
• Advantage: Single-dose, better GI tolerance
• Disadvantage: Expensive
• Role: Alternative for adherence concerns

3. Experimental Approaches:

• Paromomycin gel: Aminoglycoside, intravaginal; low efficacy (~40%)
• Boric acid: 600mg intravaginal; salvage only
• Zinc sulfate: In vitro activity; clinical data lacking
• Probiotics: L. crispatus suppositories for post-treatment flora restoration

Vaccine Development

Current Status:

• No vaccine currently available
• Challenges:
  • Antigenic variation (65 BspA genes)
  • No protective immunity after natural infection
  • Lack of animal model (TV only infects humans)

Research Directions:

• Surface protein vaccines (targeting adhesins)
• Whole-organism killed vaccines
• DNA vaccines encoding virulence factors
• Subunit vaccines (α-actinin, AP65)

Economic Burden

Healthcare Costs:

Cost-Effectiveness of Screening:

• Universal screening NOT cost-effective in low-prevalence populations (less than 5%)
• Targeted screening cost-effective in:
  • High-prevalence populations (> 10%)
  • Pregnant women with symptoms
  • HIV-positive individuals
  • STI clinic attendees

Public Health and Prevention Strategies

Primary Prevention:

Secondary Prevention (Screening):

WHO Screening Recommendations:

• Symptomatic individuals: Test and treat
• Asymptomatic high-risk groups: Consider screening
• General population: NOT recommended (low yield, resource intensive)

Tertiary Prevention (Preventing Complications):

• Prompt treatment to prevent HIV transmission
• Treatment in pregnancy to prevent preterm birth
• Partner notification to prevent reinfection

Syndromic Management in Resource-Limited Settings

Where laboratory diagnosis unavailable:

Vaginal Discharge Syndrome Algorithm:

Patient with vaginal discharge
    ↓
Risk Assessment (multiple partners, STI symptoms in partner)
    ↓
IF HIGH RISK:
    → Treat for TV + Gonorrhea + Chlamydia
    (Metronidazole + Ceftriaxone + Azithromycin)
    ↓
IF LOW RISK + Normal pH + KOH negative:
    → Treat for Candida
    ↓
IF LOW RISK + High pH + Fishy odor:
    → Treat for TV + BV (Metronidazole alone)

Limitations of Syndromic Management:

• Over-treatment (many non-infectious causes of discharge)
• Under-diagnosis (asymptomatic cases missed)
• Antibiotic resistance concerns
• Cost implications

Advantages:

• No laboratory needed
• Same-day treatment
• Covers common co-infections

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15. Clinical Case Studies

Case 1: Classic Presentation

Presentation: Mrs. JK, 28-year-old woman, presents with 5-day history of offensive vaginal discharge and vulval itching. No abdominal pain. New sexual partner 3 weeks ago (unprotected intercourse). LMP 2 weeks ago.

Examination:

• Vulva: Erythematous, excoriated
• Speculum: Profuse frothy yellow-green discharge pooling in posterior fornix
• Cervix: Punctate hemorrhages visible ("strawberry cervix")
• Vaginal pH: 5.5
• Bimanual: No cervical motion tenderness

Investigations:

• Wet mount: Motile flagellated organisms visible
• NAAT: Trichomonas vaginalis detected
• Full STI screen: Also positive for Chlamydia trachomatis
• HIV: Negative

Management:

1. Metronidazole 400mg PO BD × 7 days
2. Azithromycin 1g PO stat (for Chlamydia)
3. Alcohol avoidance counseling
4. Partner notification for both infections
5. Abstain from intercourse until both treated + 7 days
6. Follow-up in 2 weeks if symptoms persist

Outcome:

• Symptoms resolved by day 4
• Partner attended, treated empirically
• Re-screen at 3 months: Negative

Learning Points:

• Co-infection with Chlamydia in 15-20% of TV cases
• "Strawberry cervix" is pathognomonic but only visible in 2% without magnification
• Partner treatment prevents reinfection (ping-pong effect)

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Case 2: Asymptomatic Male Reservoir

Presentation: Mr. AB, 35-year-old man, attends as sexual contact of confirmed TV case. Completely asymptomatic. No urethral discharge, dysuria, or genital symptoms.

Examination:

• External genitalia: Normal
• Urethral meatus: No discharge expressible
• Testes: Non-tender

Investigations:

• First-void urine NAAT: Trichomonas vaginalis POSITIVE
• Full STI screen: Otherwise negative

Management:

1. Metronidazole 2g PO stat (single dose acceptable in men with treated female partner)
2. Alcohol avoidance for 48 hours
3. Abstain from intercourse × 7 days
4. Advised that female partner must complete full course

Outcome:

• Remained asymptomatic throughout
• Test of cure not performed (asymptomatic, low-risk)

Learning Points:

• 70-90% of infected men are asymptomatic
• Men are key reservoir for transmission
• Partner notification essential to break transmission cycle
• Single-dose therapy acceptable in men (adherence, convenience)

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Case 3: Treatment Failure - Reinfection

Presentation: Ms. CD, 32-year-old woman, returns 4 weeks after completing metronidazole 400mg BD × 7 days for TV. Symptoms have recurred (discharge, itching).

History:

• States she completed full course
• Did not drink alcohol
• Resumed intercourse with regular partner 5 days after finishing treatment
• Partner was "given antibiotics" but unsure if he took them

Investigations:

• NAAT: Trichomonas vaginalis POSITIVE (recurrent)
• Culture: Organism sensitive to metronidazole (MIC less than 2 μg/mL)

Diagnosis: Reinfection (not resistance)

• Partner likely not treated or treated incorrectly
• Intercourse before both partners fully treated

Management:

1. Re-treat: Metronidazole 400mg BD × 7 days
2. Directly observed therapy for partner (brought to clinic)
   • Partner treated simultaneously with 2g stat dose in clinic
3. Strict counseling: No intercourse until BOTH completed + 7 days
4. Offer relationship/communication support

Outcome:

• Both partners treated
• 3-month follow-up: Negative

Learning Points:

• Reinfection is the most common cause of "treatment failure" (> 90%)
• Partner treatment verification crucial
• Consider supervised/observed therapy if non-compliance suspected
• Resistance is rare (less than 5%) - exclude reinfection first

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Case 4: Pregnancy Complication

Presentation: Mrs. EF, 24-year-old, G2P1, 18 weeks pregnant, presents with offensive discharge and dysuria. Worried about baby.

History:

• Symptoms started 1 week ago
• No previous STI history
• Husband denies symptoms

Examination:

• Profuse yellow-green discharge
• Cervix friable, no strawberry appearance visible
• No cervical motion tenderness
• Fundus: Appropriate for dates

Investigations:

• NAAT: Trichomonas vaginalis positive
• Full STI screen: Negative for other infections
• Urine culture: No growth

Management:

1. Treat immediately (symptomatic infection in pregnancy must be treated)
2. Metronidazole 400mg PO BD × 7 days (safe in pregnancy at all stages)
3. Counsel re: safety (no evidence of teratogenicity)
4. Husband treated: Metronidazole 2g stat
5. Abstinence until both treated
6. Test of cure at 1 month (recommended in pregnancy)

Counseling:

• Untreated TV associated with preterm birth (1.4× risk)
• Low birth weight
• Premature rupture of membranes
• Treatment reduces these risks
• Metronidazole is safe (Category B in US, extensive human data)

Outcome:

• Symptoms resolved
• Test of cure negative
• Delivered at 39 weeks, healthy baby

Learning Points:

• Symptomatic TV in pregnancy MUST be treated
• Don't avoid treatment due to pregnancy - risks of untreated infection exceed any theoretical drug risks
• 7-day course preferred over single 2g dose in pregnancy
• Test of cure recommended at 1 month
• Asymptomatic screening NOT recommended (Klebanoff trial showed no benefit, possible harm)

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Case 5: Resistant Trichomoniasis (Rare)

Presentation: Ms. GH, 29-year-old, with persistent TV despite multiple treatment courses:

• Course 1: Metronidazole 400mg BD × 7 days (symptoms recurred week 3)
• Course 2: Metronidazole 2g stat (no improvement)
• Course 3: Metronidazole 400mg TDS × 7 days (partial improvement, relapse)

Investigations:

• Sexual history: Monogamous relationship × 2 years
• Partner treated × 3 (confirmed adherence, observed)
• Abstinence maintained during treatment periods
• Culture: Trichomonas vaginalis grown
• Susceptibility testing: Metronidazole MIC 100 μg/mL (RESISTANT)

Diagnosis: Metronidazole-resistant trichomoniasis (confirmed)

Management: Referral to GUM specialist:

1. First-line for resistance: Tinidazole 2g PO daily × 14 days
2. Outcome: Symptoms resolved
3. Test of cure (culture): NEGATIVE

Alternative (if Tinidazole fails):

• High-dose combination: Metronidazole 2g + Tinidazole 2g daily × 14 days
• Intravaginal therapy: Paromomycin 250mg/g pessaries + oral tinidazole
• Experimental: Dequalinium chloride vaginal tablets

Learning Points:

• Resistance is rare (less than 5%) but increasing
• Suspect if treatment failures despite confirmed partner treatment and adherence
• Culture and sensitivity testing required (reference lab)
• High-dose tinidazole usually effective
• Specialist management essential
• Do NOT keep repeating failing regimens

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13. Examination Focus

Audit Standards (Based on BASHH Guidelines)

Quality Indicators

Process Indicators:

1. % of symptomatic vaginal discharge patients tested for TV
2. % of TV diagnoses with documented sexual history
3. % with documented partner notification discussion
4. % with documented alcohol warning

Outcome Indicators:

1. Treatment failure rate (less than 10% expected)
2. Reinfection rate at 3 months (less than 20% expected)
3. Partner treatment rate (> 70% target)
4. Patient satisfaction scores

Common Gaps in Care

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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).

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

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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.