Sexually transmitted infections

Contributed by Dr Alan McOwan, lead clinician, Victoria Clinic for HIV and Sexual Health, London.

Section 1: Dysuria and discharge.

Chlamydia is responsible for 50 per cent of pelvic inflammatory disease (PID), and is the main preventable cause of infertility.

Nearly half of all ectopic pregnancies are thought to be due to damage secondary to chlamydia infection, and ectopic pregnancy accounts for one-fifth of all deaths related to pregnancy and childbirth.

Up to 12 per cent of young women presenting in primary care are infected with chlamydia but up to 90 per cent of women infected with chlamydia are asymptomatic, and infection may persist for more than a year. Where symptoms are present, uncomplicated infection in women presents with discharge and dysuria.

Photograph: Dr P. Marazzi/SPL

Discharge is typical of gonorrhoea infection but is not always present

Re-infection is a common cause of treatment failure, so sexual partners must be treated and intercourse stopped until treatment is completed.

Treatment of uncomplicated chlamydia is with doxycycline 100mg twice daily for seven days, or azithromycin 1g orally as a single dose.

Incidence of gonorrhoea has risen dramatically since the mid-1990s, most markedly in 16- to 19-year-olds. Typical symptoms, if present, are discharge and dysuria. It is difficult to differentiate between chlamydia and gonorrhoea clinically.

Polymerase and ligase chain reaction tests are DNA amplification tests, and can identify the infection by detecting tiny quantities of the organism's DNA.

It is worth noting that chronic Bartholin's infection can be caused by gonorrhoea.

Treatment is a single dose of either ceftriaxone 250mg IM or cefixime 400mg orally.

Trichomonas typically causes an offensive, thin, frothy discharge, often with vulval soreness, swelling and itching. Diagnosis is on microscopy or culture. Although it is sometimes reported on cervical cytology results, this is not a diagnostic test due to the low sensitivity.

Treatment is metronidazole either as a 2g single dose, or 400mg twice daily for five days.

Bacterial vaginosis
Bacterial vaginosis (BV) is often diagnosed by a typical fishy smelling discharge alone, but the discharge should fulfil three of the four 'Amsel criteria': a thin, white vaginal discharge; a positive amine smell after adding potassium hydroxide; a pH greater than 4.5; and clue cells present on Gram staining. Pain and irritation are not typical.

BV is an overgrowth of anaerobic organisms and is not sexually transmitted. Treatment of sexual partners is not required and does not affect recurrence rates. It is most common at the end of a menstrual cycle and may resolve spontaneously after menstruation. It is more common in smokers and IUD users, and black women seem more prone than white.

Oral treatment is with metronidazole 400mg twice daily for five days. Intravaginal metronidazole gel (0.75%) daily for five days or intravaginal clindamycin 2% cream daily for seven days are also effective.

It has been shown that if pregnant women with BV who have a history of preterm or second-trimester labour are given oral metronidazole early in the second trimester, the chance of early labour is reduced.

Candida is the commonest cause of abnormal vaginal discharge. Overgrowth of candida in women causes a thick, white, lumpy vaginal discharge with associated itching, soreness or superficial dyspareunia. In men, candida can cause a balanitis.

Many women diagnosed with 'chronic' or recurring thrush have underlying dermatological conditions such as eczema or psoriasis. Clues include a history of atopy, and a partial response to candida treatments, and vulval itching without typical discharge. Washing with aqueous cream may help but improvement may take several weeks.

Management of recurrent episodes should consider iatrogenic factors such as oral steroids or antibiotics. Urine should be tested for glucose, and dermatoses considered. The patient should avoid local irritants.

Treatments include a single clotrimazole pessary (500mg), econazole pessary (150mg) or oral fluconazole 150mg as a single dose.

Section 2: Genital ulceration
It is important to be able to distinguish the main causes of genital ulceration.

Herpes simplex
Herpes simplex is the most common ulcerative STI in the UK. Lesions typically start as fluid-filled blisters that burst to leave multiple small, painful ulcers. Asymptomatic infection is common, and about 25 per cent of the population have serological evidence of infection.

Most do not have clinically obvious attacks, but episodic shedding of the virus may occur. This means that primary attacks may present within monogamous relationships.

Oro-genital transmission is common. Asymptomatic shedding is more common in symptomatic individuals just before or immediately after an attack.

Treatment of primary attacks with antivirals offers a significant improvement in healing time, but this effect is less for recurrences. Saline bathing and analgesia with NSAIDs can help.

Prophylaxis is appropriate in those whose recurrences have a significant impact on lifestyle, but these patients should be referred for specialist opinion.

Between 1996 and 2007 there has been a 1,665 per cent increase in the diagnosis of infectious syphilis in the UK.1 The majority can be attributed to outbreaks in Manchester, Brighton and London.

Although HIV-positive gay men appear to be at highest risk, rates are rising fast in heterosexual women in their 20s. One in eight cases in 2005 were acquired outside the UK. The presence of an ulcerative genital condition increases the risk of HIV transmission sixfold.

The typical ulcers of primary syphilis differ from herpetic lesions in that they are large (0.5-2cm across), often single, painless and usually occur about a month after infection.

Secondary syphilis typically occurs six to eight weeks after infection, and may be characterised by a widespread maculopapular rash involving the palms and soles.

Untreated syphilis typically becomes less infectious two years after the initial infection.

Untreated patients may develop tertiary syphilis, with cardiac complications (10 per cent), neurosyphilis (7 per cent) or tumours (16 per cent).

Serology for syphilis should be part of investigating dementia and unexplained neurological symptoms. Routine screening for syphilis should be performed in pregnant women.

Herpes history

  • Painful
  • Multiple
  • Viral symptoms
  • Previous history

Syphilis history

  • Painless
  • Usually single
  • Travel history

Section 3: Lumps and other lesions
Genital warts and molluscum contagiosum are the most commonly encountered lesions.

Genital warts
Visible genital warts are the most common viral STI in the UK. They usually appear as fleshy growths on areas subject to friction during sex, such as vaginal and anal orifices and the frenulum of the penis. They are characterised by an irregular cauliflower-like surface. Asymptomatic carriage is common.

Nearly all visible warts are caused by HPV types 6 and 11, but it is types 16, 18, 31, 33 and 35 that are associated with over 90 per cent of cervical cancers.

This means that women with visible genital warts are no more likely to have cervical infection with the types linked to cancer than those without, so they do not need additional cervical cytology. Cytology should be guided by previous cytology findings alone.

Topical preparations such as podophyllotoxin and imiquimod allow self-treatment at home, but podophyllotoxin is less useful for keratinised (hard) warts. Other treatment options include trichloracetic acid, electrocautery, hyfrecation or surgery. Treatments other than immune modulators aim to remove the wart and not the virus, so recurrence is common.

The incubation period is highly variable, and subclinical infection is common. This may account for the development of genital warts in monogamous relationships.

Genital warts are almost without exception acquired during sex. Patients can be reassured that transmission between hands and genitals does not occur in adults.

One in 10 people with a new diagnosis of genital warts also has a second STI. Therefore, referral for full STI screening is recommended.

Warts and pregnancy
Warts may recur or increase in size during pregnancy, but podophyllin-related products such as Warticon and Condyline are contraindicated in pregnancy due to the risk of teratogenesis.

Between one in 200 and one in 1,000 women with visible warts may pass infection to the child during delivery, causing laryngeal papillosis.

Molluscum contagiosum
Molluscum contagiosum on the genitals are usually sexually transmitted and can be differentiated from warts by their typical central umbilication.

Lightly freezing the area may highlight the umbilicus and aid diagnosis.

Patients should not shave the area as this spreads the lesions. The condition is self-limiting and recurrence is less common than with genital warts.

Treatments include curettage and cryotherapy. There is evidence that imiquimod and podophyllotoxin are effective, although neither treatment is licenced for this purpose.

Section 4: Itching and rashes
Scabies and pubic lice are frequently implicated as the cause of genital irritation and rashes.

Scabies is spread by close contact. Symptoms may be delayed up to four weeks after acquisition. The itching experienced by patients is due to an allergic reaction to the mite, its saliva and faeces. The itch does not indicate the site of the mites.

Scabies infestation: burrows may be seen between the fingers

Symptoms are made worse by warmth, for example after a bath or in bed. Burrows may be visible in the finger webs and, when sexually acquired, they are commonly seen on the penis as raised lumps.

A faint bilateral pink rash is often present over the entire body but spares the face and the central chest and back. This is due to hypersensitivity and does not indicate the site of the mites.

Washing bedding and clothing during treatment is not usually necessary.

The reaction typically takes up to two weeks to subside. Continued itching in this period does not indicate treatment failure, although the appearance of new burrows does.

Treatments include malathion lotion left on the skin for 24 hours or permethrin lotion left on the skin for 12 hours. Both are repeated after a week.

Failure of treatment
If there is no response to treatment, there may be reinfection. This can occur if all contacts are not treated concurrently.

Other explanations for failure include handwashing, or failure to apply lotion under the fingernails. Patients should be advised not to apply treatment repeatedly as this can cause an irritant dermatitis.

Pubic lice
Unlike scabies, pubic lice (crabs) may survive for up to two hours away from the body, but are usually spread by intimate contact.

Itching is caused by acquired sensitivity. Those who have had previous infection have a rapid onset of symptoms.

Egg cases (nits) are commonly seen attached to the pubic hair. The lice may be seen in underwear. Treatment with malathion lotion left on the skin for 12 hours may not kill eggs, and reapplication is advised after one week. The empty egg cases will remain stuck to the hair until it grows out, so this is not a sign of treatment failure. They can be removed with a nit comb.



1. Health Protection Agency. Health Protection Report: HIV/Sexually Transmitted Infections. 31 Oct 2008; 2(44).

Further reading

  • M Adler (Ed). The ABC of Sexually Transmitted Infections, Fifth Edition. London: BMJ Publishing Group.
  • A Wisdom, D Hawkins. Diagnosis in Colour. Sexually Transmitted Diseases. London: Mosby, 1997.


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