Comprehensive STI Revision Notes

General Features of Sexually-Transmitted Infections (STIs)

  • Asymptomatic nature
    • Most STIs give no symptoms or delay symptom onset.
    • HPV: vast majority are unaware they ever had it.
    • Early symptom-presenters occasionally show signs within ≈ 1 week.

  • Under-estimation of risk
    • Patients regularly “down-play” both STI and unintended-pregnancy risk.
    • Common self-rationalisation: “I’ve had sex a few times and nothing happened, so I must be low-risk / low-fertility.”

  • Bacterial vs viral prognosis
    • Bacterial infections (chlamydia, gonorrhoea, early syphilis) typically curable with single-dose or short-course antibiotics.
    • Viral infections:
    – Hepatitis C now mostly curable (though rarely sexually transmitted).
    – HIV, HSV (herpes), HPV: not yet eradicable; management is suppression + prevention.

  • Numerical timelines
    • HPV high-risk types → cancer in \ge 10 (usually 20\text{–}30) yrs.
    • Untreated syphilis: tertiary manifestations after 5\text{–}30 yrs.

Prevention & Barrier Methods

  • External (male) condom
    • When applied before any genital contact and used correctly, protection against most STIs is \approx 90\text{–}99\%.

  • Female (internal) condom
    • Extra external-skin coverage → probably slightly better for HPV/HSV than male condom.

  • Dams
    • Flavoured latex squares for oral–vulval / oral–anal contact.
    • Decrease HSV and partially decrease HPV, chlamydia, gonorrhoea.

  • Diaphragm
    • Minimal STI protection; may reduce chlamydia/gonorrhoea a little; ineffective for syphilis or HPV.

  • Saliva transmission recap
    • Hep B: yes.
    • Chlamydia/Gonorrhoea: possible.
    • HPV, HSV, trichomonas, syphilis, HIV: no via saliva alone.

Human Papillomavirus (HPV)

  • Epidemiology
    • Historically most common STI.
    • Vaccination (Gardasil 9) now sharply reducing genital-wart presentations (clinician saw last case ≈ 18 months ago).
    • Gardasil 9 composition: 7 high-risk + 2 low-risk (wart) serotypes.

  • Clinical spectrum
    • Low-risk types → genital warts (cosmetic/irritative).
    • High-risk types → cervical, anal, penile, oropharyngeal cancers.

  • Natural history
    • In immunocompetent host, virus usually clears; persistence over \ge 10 yrs produces dysplasia/cancer.

  • Screening
    • Australian cervical screening: HPV test from age 25; earlier if symptoms.

  • Prevention
    • Vaccination at school age.
    • Condoms/dams >90\% protective (not 100 %).

  • Treatment of warts
    • Self-applied imiquimod/Podophyllotoxin vs in-clinic cryotherapy.
    • Recurrence common because surrounding skin still infected.

Herpes Simplex Virus (HSV-1 & HSV-2)

  • Lesions
    • Usually few, small vesicles → shallow ulcers; severe photos shown (coalesced large ulcers).
    • May be asymptomatic or present with tingling/itch only.

  • Transmission windows
    • Highest during lesions & \pm 1 week, but low-level shedding anytime.

  • Vertical transmission
    • Primary episode near delivery → neonatal encephalitis, high mortality ⇒ elective C-section often advised.

  • Prevention
    • Condoms/dams >90\% protective.
    • Daily suppressive antivirals (e.g.
    aciclovir/valaciclovir) cut partner-transmission risk.

  • Diagnosis
    • PCR swab from any suspicious ulcer/split; blood tests unreliable (false-positives, location unknown).

  • Management
    • Episodic antivirals at prodrome, saline baths, analgesia.
    • Suppressive therapy for frequent recurrences.
    • Psychosocial counselling often needed.

Chlamydia trachomatis & Neisseria gonorrhoeae

Shared Features

  • Prevalence
    • Chlamydia: commonest bacterial STI; highest in 15\text{–}25 yr age-group.
    • Gonorrhoea: rising, still < chlamydia.

  • Complications
    • Men: epididymo-orchitis (hot, swollen scrotum).
    • Women: PID → tubal scarring, hydrosalpinx ⇒ sub-fertility, chronic pelvic pain.
    • Both: reactive arthritis.

  • Testing timing
    • Screen \ge 1 week after unprotected sex.

Presentation Clues

  • Dysuria, mucous/purulent discharge, new pelvic pain, new period pain, inter-menstrual or post-coital bleeding.

  • Gonorrhoea discharge often thicker & yellow.

Investigations

  • Screening
    • Women: self-collected low-vaginal swab (better) or first-void urine (FVU).
    • Men: FVU.

  • Symptomatic
    • Culture swab of any discharge + NAAT.

Treatment (2023 guideline update)

  • Chlamydia
    • Preferred: doxycycline 100\,\text{mg} BD × 7 days.
    • Alternative: azithromycin 1\,\text{g} single dose (for poor pill-takers).

  • Gonorrhoea
    • IM ceftriaxone (with lignocaine) + oral azithromycin (dose per local guideline).
    • Emerging antibiotic resistance only a concern for gonorrhoea (not chlamydia) in Australia.

Partner management

  • Test & empiric treat partners from past 3 months.

  • Anonymous notification available when patient cannot inform.

Prevention

  • Condoms > 95\% effective if perfect/consistent.

Trichomonas vaginalis

  • Epidemiology
    • Uncommon in Perth; higher in some rural/remote WA regions.

  • Clinical
    • Women: frothy, malodorous discharge, vulval irritation; intensely inflamed, “beefy red” vagina/cervix on speculum.
    • Men: usually asymptomatic; occasionally mild urethritis/skin irritation.

  • Public-health importance: increases HIV transmission risk significantly.

  • Diagnosis
    • Must request specifically (not on routine NAAT).
    • Swab during speculum if “froth & bubble” seen.

  • Treatment
    • Metronidazole (patient & sexual partner[s]).

  • Prevention
    • Condoms highly effective.

Syphilis (Treponema pallidum)

  • Current trend
    • Rising incidence beyond remote areas & MSM; now includes heterosexual men & women with some unprotected sex.

  • Stages
    • Primary: painless chancre(s); ± tender inguinal nodes.
    • Secondary: rash incl. palms/soles, mucous patches, condylomata lata, patchy alopecia, eyebrow loss.
    • Latent: asymptomatic + serology-positive.
    • Tertiary (5\text{–}30 yrs): neurosyphilis, tabes dorsalis, aortic aneurysm, gummatous skin lesions, sensorineural deafness, vision loss.
    • Congenital: crosses placenta → miscarriage, stillbirth, neonatal disease, long-term disability.

  • Diagnosis
    • Serology mainstay; PCR of ulcer if visible.

  • Treatment
    • Benzathine penicillin G (single IM dose for early), longer courses for late/unknown duration.
    • Tertiary damage may be irreversible.

  • Prevention considerations
    • Condoms good but lesions outside covered area still transmit.

Hepatitis B Virus (HBV)

  • Acute infection
    • Flu-like illness, anorexia, nausea, jaundice; rare fulminant hepatic failure & death.

  • Chronic infection risk
    • Small percentage progress → cirrhosis or hepatocellular carcinoma.

  • Transmission
    • Perinatal (childbirth), blood (needles, sharps), sex, saliva & other body fluids.

  • Prevention
    • Vaccination: childhood + catch-up programs.
    • Condom use; strict single-use injecting equipment.

  • Treatment
    • Long-term antivirals suppress viral replication (not curative yet, unlike modern Hep C therapy).

Human Immunodeficiency Virus (HIV)

  • Untreated natural history
    • Gradual CD4 decline → opportunistic infections & malignancies → death ≈ 12 months after AIDS onset.

  • Treatment revolution
    • Modern ART (1–2 pills OD/BID) = near-normal life expectancy.

  • Acute seroconversion illness
    • 2\text{–}4 weeks post-exposure: high fever, cervical lymphadenopathy, rash.
    • Testing becomes positive at that point.

  • Window period
    • Most serology positive by 6 weeks; definitive negative at 3 months.

  • Per-act transmission risks (if source is untreated, no condoms)
    • Blood transfusion with infected blood: \approx 92\%.
    • Receptive anal sex: highest genital-related risk.
    • Penile–vaginal: female receptive risk > male receptive risk.
    • Oral sex: no documented cases, effectively negligible.

  • Prevention hierarchy
    • Condoms (very high efficacy).
    • PrEP (daily tenofovir/emtricitabine) \approx 99\% effective.
    • PEP (within 72 h, for 28 days) for occupational or sexual exposures.
    • Treat-all strategy: “U=U” (Undetectable viral-load = Untransmittable).

Screening & Testing Cheat-Sheet

  • Annual chlamydia/gonorrhoea screen for 15\text{–}25 yr sexually active individuals.

  • Test \ge 1 week post exposure for C/G; serology at 6 weeks & 3 months for HIV.

  • Cervical HPV screen from 25 yrs ➝ 5-yearly if negative.

  • Syphilis serology in pregnancy, high-risk groups, or if symptoms/rash.

  • Trichomonas test only if symptomatic + visual/frothy discharge.

Treatment Principles & Logistics

  • Single-dose cures: azithromycin 1\,\text{g} (chlamydia option), IM benzathine penicillin (early syphilis), IM ceftriaxone (gonorrhoea, when combined with azithro).

  • Course treatments: doxycycline 7 days, HSV antivirals episodic/suppressive, HBV long-term nucleos(t)ides, lifelong ART for HIV.

  • Partner treatment / contact tracing: vital to prevent reinfection & wider spread; clinics offer anonymous notification if patient unable.

  • Resistant organisms: monitor gonorrhoea; follow evolving guidelines.