Section 5-3: Canadian Guidelines on Sexually Transmitted Infections – Management and treatment of specific infections – Ectoparasitic infestations

Section 5 - Management and Treatment of Specific Infections

Ectoparasitic Infestations (Pubic Lice, Scabies)

Pubic Lice

Etiology/Epidemiology

• Caused by Phthirus pubis (crab louse).
• Humans are the only reservoir.
• Shorter life span off host (24 hours) than head lice (several days).
• Usually present in pubic hair, but may also be found in chest, armpits, eyelashes or facial hair.
• Transmission occurs through intimate sexual and non-sexual contact.^{Footnote 1}

Prevention and Control

• Patients presenting with concerns about sexually transmitted infections (STIs) and/or prevention of pregnancy should be provided with instructions and encouragement about the consistent practice of safer-sex.
• At the time of diagnosis, review and monitor prevention practices.
• Identify barriers to prevention practices and the means to overcome them.
• See Primary Care and Sexually Transmitted Infections chapter.

Manifestations^{Footnote 2}

• Itching, scratching, erythema, skin irritation and inflammation, all as a reaction to the louse bite.
• Small blue spots can appear where the louse has bitten.
• Extensive infestation can be associated with mild fever and malaise.
• Scratching can lead to a secondary bacterial skin infection.

Diagnosis

• Based on history and index of suspicion.
• Careful examination for adult lice and eggs (nits). Look for an area of scabs with nits in the hair; scabs may be adult lice. Nits attach to hair and are not loose and flaky.

Specimen collection and laboratory diagnosis

• If necessary, submit nits or scabs in a container for microscopic examination.

Management

• Clothes, bedding and fomites: washing in hot water (50˚C) or dry cleaning kills all stages of lice. Alternatively, place in plastic bags for 1 week.
• Vacuum mattresses.
• Sexual partner(s) within the last month should be treated.
• May re-treat after 1 week if no clinical improvement. Pruritus may be controlled with antihistamines such as hydroxyzine or diphenhydramine, as well as mild topical corticosteroids.^{Footnote 2}

Treatment

• Wash the affected area and apply pediculocide formulation (cream, lotion or shampoo) according to package instructions.
  • Permethrin 1% cream [A-l]
    
    OR
  • 0.33% pyrethrin-piperonyl butoxide shampoo [A-l]
    
    OR
  • lindane 1% shampoo [A-l]^{Footnote 2,Footnote 3}
• May repeat in 3 -7 days.

Special Considerations

• Pediculosis of the eyelashes should not be treated with permethrin, pyrethrin or lindane.^{Footnote 2} Recommended treatment: occlusive ophthalmic ointment to the eyelid margins bid for 10 days.
• Gamma benzene hexachloride (lindane) can cause neurotoxicity. Instructions for use must be carefully followed to minimize risk of toxicity.^{Footnote 3} Contraindicated in children <2 years of age, in pregnancy, in lactating women or in patients with extensive dermatitis.
• Permethrin cream has efficacy similar to lindane 1%, with less toxicity and cure rates greater than 80%.^{Footnote 3}
• Pruritus may persist for several days or weeks after treatment.
• In patients with excoriated or damaged skin, consider dose modification to compensate for increased absorption of topical agents.

(See below for Consideration for Other STIs, Reporting and Partner Notification, and Follow-up).

Scabies

Etiology/Epidemiology

• Caused by Sarcoptes scabiei.
• Incubation period is 3 weeks, but reinfestation provokes immediate symptoms (1 to 3 days).^{Footnote 1}
• Transmission:
  • Often non-sexual, through close person-to-person contact (e.g., in families and institutions).^{Footnote 4}
  • May be via shared personal articles (clothes, bedding).
  • Sexual transmission does occur; usually need more than brief contact.

Prevention and Control

• Patients presenting with concerns about STIs and/or prevention of pregnancy should be provided with instructions and encouragement about the consistent practice of safe-sex.
• At the time of diagnosis, review and monitor prevention practices.
• Identify barriers to prevention practices and the means to overcome them.
• See Primary Care and Sexually Transmitted Infections chapter.

Manifestations

• Intense nocturnal itching.
• Burrows under the skin.
• Lesions affecting hands (finger webs, sides of digits), flexor surfaces of the wrists, axillae, waist, nipple areola, periumbilical area and male genitalia.^{Footnote 5}
• Papules or nodules, which result from itching, often affect the genital area.
• Pyoderma of the penis.
• HIV-infected patients may present atypically with crusted or “exaggerated” scabies called Norwegian scabies.^{Footnote 6}

Diagnosis

• Based on history, index of suspicion and examination.
• Diagnosis is often difficult and therefore delayed.

Specimen collection and laboratory diagnosis

• If necessary, take a skin scraping of a burrow to remove the mite or ova for microscopic examination.^{Footnote 1}
• Burrow ink test: apply fountain pen ink or a washable marker to outside of burrow, wipe skin (with alcohol). Burrows will retain the ink and may be visualized.^{Footnote 2}

Management

• Clothes, bedding and fomites: washing in hot water (50˚C) or dry cleaning kills all stages of the organism. Alternatively, place in plastic bags for 3 days to 1 week.^{Footnote 1}
• Vacuum mattresses.
• All household contacts and recent sexual partner(s) in the last month should be treated.
• Pruritus may persist for several weeks. Pruritus may be controlled with antihistamines and mild topical corticosteroids.

Treatment

• Permethrin 5% cream [A-l].^{Footnote 2,Footnote 3,Footnote 7}
  • Apply to the body from the neck down; leave for 8 to 14 hours; shower and wear clean clothes.
  OR
• Gamma benzene hexachloride (lindane) 1% cream or lotion [A-l].^{Footnote 2,Footnote 3,Footnote 7,Footnote 8}
  • Apply to the body from the neck down; leave for 8 hours; shower and wear clean clothes.
  • More potential for toxicity than permethrin.
  • Contraindicated in children <2 years of age, in pregnancy, in lactating women or in patients with extensive dermatitis.
• Alternatives:
  • Crotamiton 10% cream [A-l] (less effective than permethrin or lindane).^{Footnote 7,Footnote 9} This product is available through the Health Canada Special Access Program.
    • Apply nightly for two nights and wash off thoroughly 24 hours after last application.
    OR
  • Sulphur 5% in petroleum [A-l] (less effective than permethrin or lindane).^{Footnote 7,Footnote 9}
    • Apply nightly for three nights and wash off thoroughly 24 hours after last application.

Special Considerations

• In pregnancy, permethrin is the only agent that should be used.^{Footnote 2}
• Gamma benzene hexachloride (lindane) can cause neurotoxicity. Instructions for use must be carefully followed to minimize risk of toxicity.^{Footnote 3} Contraindicated in children <2 years of age, in pregnancy, in lactating women or in patients with extensive dermatitis.
• In patients with excoriated or damaged skin, consider dose modification to compensate for increased absorption of topical agents.

Consideration for Other STIs

• See Primary Care and Sexually Transmitted Infections chapter.
• Obtain a specimen for the diagnosis of Chlamydia trachomatis and Neisseria gonorrhoeae.
• Obtain a blood sample for serologic testing of syphilis (see Syphilis chapter).
• HIV counselling and testing are recommended (see Human Immunodeficiency Virus Infections chapter).
• Immunization against hepatitis B is recommended, unless already immune (see Hepatitis B Virus Infections chapter).

Reporting and Partner Notification

• Pubic lice and scabies are not reportable to local public health authorities.
• Partner notification of ectoparasitic infestations is not required.

Follow-up

• Follow up only if clinically necessary.

References