Review - STIs - Part two

THE ESSENTIALS 

- Chlamydia screening has significant health benefits.

- Undiagnosed genital ulceration should be referred.

- Chronic thrush often represents an undiagnosed skin condition.

- Genital warts and cervical cancer relate to different subtypes of HPV.

- Scabies and pubic lice should be re-treated after one week.

1. DYSURIA AND DISCHARGE

There are a number of causes of dysuria and discharge in men and women (see box).

Chlamydia - Chlamydia is a significant cause of morbidity in the UK. It 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 caused by to damage secondary to chlamydia infection, and ectopic pregnancy accounts for one fifth of all deaths related to pregnancy and childbirth.

The problem is that up to 90 per cent of women infected with chlamydia are asymptomatic and infection may persist for more than a year. Uncomplicated infection in symptomatic men and women presents with discharge and dysuria.

Re-infection is a common cause of treatment failure, so sexual partners must be treated.

Screening for chlamydia - Pilot screening programmes in Portsmouth and the Wirral showed prevalence rates as high as 12 per cent in young women attending their GP. A very low index of suspicion is required in young people, because the peak incidence is at 16-19 years in females and 20-24 years in males. Rates are increasing rapidly in these two groups.

In countries with established chlamydia screening programmes, rates of PID and ectopic pregnancy have fallen dramatically. A community screening programme is currently rolling out in England.

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

Gonorrhoea - In the mid-1980s, the incidence of gonorrhoea declined rapidly, possibly because of changes in sexual behaviour following the initial media coverage of HIV. However, since the mid-1990s, infection rates have risen dramatically, most markedly in 16-19-year-olds. African-Caribbean populations have a disproportionately high prevalence of gonorrhoea in England and Wales.

Asymptomatic carriage occurs in about half of infected women, and more frequently in pharyngeal and rectal gonorrhoea. Typical symptoms, if present, are discharge and dysuria. It is difficult to differentiate clinically between chlamydia and gonorrhoea.

DNA amplification tests, such as polymerase and ligase chain reaction tests, can identify the infection by detecting tiny quantities of the organism's DNA. This means that urine screening for asymptomatic carriage of gonorrhoea and chlamydia should become widely available, which could revolutionise STI control in the UK.

Treatment is either ceftriaxone 250mg IM in a single dose, or cefixime 400mg orally as a single dose.

Non-specific urethritis - Non-specific urethritis (NSU) in men presents evidence of inflammation on a urethral smear and other STIs must be excluded. Mycoplasma and Ureaplasma parvum have been implicated, but routine testing is unhelpful because they may be commensals. Treatment of female sexual contacts is recommended to prevent recurrence or PID. There is no test for NSU in women. Treatment includes azithromycin 1g as a single dose or doxycycline 100mg twice daily for seven days.

KEY POINTS

- Chlamydia is often asymptomatic.

- Complications include pelvic inflammatory disease, ectopic pregnancy and infertility.

- A screening programme for chlamydia is now rolling out in England.

- Gonorrhoea infection is increasing rapidly in the young.

PRINCIPAL CAUSES OF DISCHARGE
Men Women
- Gonorrhoea - Gonorrhoea
- Chlamydia - Chlamydia
- Non-specific urethritis - Trichomonas vaginalis
- Candida
- Bacterial vaginosis

2. NON-STI CAUSES OF VAGINAL DISCHARGE

The main non-STI causes of vaginal discharge are bacterial vaginosis (BV) and candida infection.

Bacterial vaginosis In practice, BV is often diagnosed by the presence of a typical fishy smelling discharge alone, but the discharge should fulfil three of the four Amsel criteria.

These are a thin white vaginal discharge, a positive amine smell after adding potassium hydroxide, a discharge pH of greater than 4.5 and clue cells present on Gram staining. Pain and irritation are not typical features.

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 to be more prone to BV than white women.

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. Women who have recurrent BV should be advised to avoid vaginal douching, bath additives, bubble baths, antiseptics and shower gel, and should not shampoo their hair in the bath.

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

Candida Candida is the most common cause of an 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.

Treatment of asymptomatic male contacts does not reduce recurrence in women. Low-dose combined contraceptive pills are not linked to an increased incidence of symptomatic candida.

Recurrent thrush Many women diagnosed with 'chronic' or recurring thrush usually 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 be helpful, but improvement of symptoms may take several weeks.

Management of recurrent episodes should include dealing with iatrogenic factors, such as oral steroids or antibiotics. The urine should be checked for glucose, and dermatoses considered. The patient should avoid local irritants.

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

KEY POINTS

- Bacterial vaginosis can be suspected by the typical fishy smelling discharge.

- Treatment of sexual partners is not required.

- Treatment of asymptomatic men does not reduce the recurrence rate in women.

- People with 'recurrent' thrush may have an underlying dermatological condition.

3. GENITAL ULCERATION

It is important to be able to distinguish the main causes of genital ulceration (see box).

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 have no clinically obvious attacks, but episodic shedding of the virus can occur. This means primary attacks might often 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 lessened when treating recurrences.

Saline bathing and NSAIDs can help. Prophylaxis is appropriate in patients whose recurrences have significant impact on lifestyle, but they should be referred to a specialist.

Syphilis

There have been recent outbreaks of syphilis in Bristol, Manchester, Brighton and London.

Up to 50 per cent of these syphilis cases are also HIV-positive. The presence of an ulcerative genital condition increases the risk of HIV transmission by six times.

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. If ulceration is not typically herpetic, the patient should be referred to a GUM service for dark ground microscopy and syphilis serology.

Secondary syphilis typically occurs six to eight weeks after infection and can be characterised by a widespread maculopapular rash that unusually often involves the palms and soles.

Untreated syphilis typically becomes less infectious two years after the initial infection. Patients who are untreated can develop tertiary syphilis, with the development of cardiac complications (10 per cent), neurosyphilis (7 per cent), or tumours (16 per cent). Serology for syphilis should form part of any investigations requested for dementia and unexplained neurological symptoms. Routine screening for syphilis is carried out in pregnancy.

KEY POINTS

- Herpes simplex is the most common ulcerative STI in the UK.

- About 25 per cent of the population have serological evidence of herpes infection; most have no clinically obvious attacks.

- About 50 per cent of syphilis cases are also HIV-positive.

- If ulceration is not typically herpetic, refer the patient to a GUM clinic.

TYPES OF GENITAL ULCERATION
Herpes history Syphilis history
- Painful - Painless
- Multiple - Usually single
- Viral symptoms - Travel history
- Previous history

4. 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 more than 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 warts.

Other treatment options include trichloracetic acid, electrocautery, hyfrecation, or surgery. Treatments other than immune modulators, such as imiquimod, aim to remove the wart, not the virus, so recurrence is common. The incubation period is variable and sub-clinical infection is a common occurrence. This can account for the development of genital warts in monogamous relationships.

Anal warts can occur in patients who do not have anal sex. 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, so referral for full STI screening is recommended.

Warts and pregnancy

Warts can recur or increase in size during pregnancy, but podophyllin-related products are contraindicated in pregnancy, owing to the risk of teratogenesis.

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

Molluscum contagiosum

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

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

Patients should not shave the area because this spreads the lesions. Recurrence is less common than in genital warts. Treatments include curettage and cryotherapy.

KEY POINTS

- Warts are not transmitted between hands and genitals.

- Cervical cytology in women with genital warts should be guided by previous cytology findings alone.

- Podophyllin-related products are contraindicated in pregnancy because they might be teratogenic.

- Molluscum contagiosum on the genitals in adults is usually sexually transmitted.

5. ITCHING AND RASHES

Scabies and pubic lice are frequently implicated as the cause of genital irritation and rashes.

Scabies

Scabies is spread by close bodily contact. The symptoms can be delayed up to four weeks after acquisition. Itching is due to an allergic reaction to the mite, its saliva and faeces. The itch does not indicate the site of the mites.

Symptoms are made worse by warmth, such as after a bath or in bed. Burrows may be visible in the finger webs and when sexually acquired, burrows are commonly seen on the penis. A faint bilateral pink rash is often present over the body, sparing the face and the central chest and back. This is due to hypersensitivity and again, 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 during this period does not indicate treatment failure, but the appearance of new burrows does. Treatments include malathion lotion left on the skin for 24 hours and repeated one week later. Permethrin lotion should be left on the skin for 12 hours and repeated after a week.

Failure of treatment

If there is no response to treatment, there might be reinfection. This can occur if all contacts are not treated concurrently. At least two weeks should have lapsed for symptoms to have settled.

Pubic lice

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

KEY POINTS

- Symptoms of scabies might be delayed up to four weeks after acquisition.

- A faint bilateral pink rash, often present over the entire body, is due to hypersensitivity.

- Pubic lice can survive for up to two hours away from the body.

- Egg cases (nits) are commonly seen attached to the hair.

FURTHER RESOURCES

Further reading

Adler M (ed). The ABC of Sexually Transmitted Infections. BMJ Books, 2002

Wisdom A, Hawkins D. Diagnosis in Colour. Sexually Transmitted Diseases.

Mosby-Wolfe, 1997 Websites

See Medicine on the Web, page 52.

Previously in Clinical Review

You can print an A4 copy of any Clinical Review published in the past year by logging on to GPonline.com. Recent issues have covered:

- STIs - part one (3 March)

- Shoulder problems - part two (24 February)

NEXT WEEK: Coeliac disease, by Dr Andrew V Thillainayagam.

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