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.
ManifestationsFootnote 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
- Permethrin 1% cream [A-l]
- 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.
- 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.
- 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.
- 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.
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
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