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© Copyright Annals of Internal Medicine, 2014
Ann Int Med. 161 (3): ITC3-1.
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© Copyright Annals of Internal Medicine, 2014
Ann Int Med. 161 (3): ITC3-1.
in the clinic
Common
Cutaneous
Parasites
© Copyright Annals of Internal Medicine, 2014
Ann Int Med. 161 (3): ITC3-1.
Clinical Overview
 Common skin parasites
 Scabies (Sarcoptes scabiei var. hominis mite)
 Bedbug (Cimex lectularius)
 Lice (Pediculus humanus capitis, Pediculus humanus
humanus, Pthirus pubis)
 Fleas
© Copyright Annals of Internal Medicine, 2014
Ann Int Med. 161 (3): ITC3-1.
Are there particular patient populations or
living situations in which adults should be
screened for common cutaneous parasites?
 Scabies
 Elderly persons; sexually active young adults; homeless;
people in institutional settings
 Associated with overcrowding, poor living conditions
 Most common animal vector to humans: pet dogs
 Crusted scabies (mite hyperinfection)
 If immune system unable to control mite replication
 If patient has reduced sensation, neurologic disorder,
physical or mental debilitation
continued…
© Copyright Annals of Internal Medicine, 2014
Ann Int Med. 161 (3): ITC3-1.
 Bedbugs
 Risks: overnight at new home, hotel, hospital, dorm room
 Lice
 Head : common, especially among girls 3-12 y
 Body: urban homeless; adults in overcrowded conditions
 Pubic: more common in men; often sexually transmitted
 Fleas (cat, dog, rat)
 Owning or working with animals increases infestation risk
© Copyright Annals of Internal Medicine, 2014
Ann Int Med. 161 (3): ITC3-1.
Should schools screen for head lice?
 Head lice
 Routine school screening doesn’t reduce incidence
 If infestation found, parents should get education on how
to diagnose and manage
 Body lice
 Consider screening homeless populations
 Once infestation identified, consider screening persons
living in crowded conditions
 Pubic lice
 Don’t screen asymptomatic patients
© Copyright Annals of Internal Medicine, 2014
Ann Int Med. 161 (3): ITC3-1.
CLINICAL BOTTOM LINE: Clinical
overview...
 Do screen: those in contact with patients who have
scabies, lice
 Patients with pubic lice should notify their partners
 Don’t screen: school-wide screening for head lice not
recommended
 Reservoirs for fleas: domestic animals & rodents
 Treat the animals or prevent human contact with them
© Copyright Annals of Internal Medicine, 2014
Ann Int Med. 161 (3): ITC3-1.
Is clinical diagnosis sufficient for diagnosis
or are laboratory tests sometimes needed?
 Scabies
 Diagnose primarily by history and physical exam
 Pruritic burrows at web spaces of fingers, genitalia
 Harvest mite, ova, or fecal pellets by scraping laterally
across the skin at a burrow site
 Skin biopsy may reveal mites surrounded by inflammatory
cells
 Scybala and chitin may fluoresce with a Wood lamp
 Mites may stain with gentian violet
 Crusted scabies: systemic levels of interleukin 4 and
peripheral IgE may be elevated
continued…
© Copyright Annals of Internal Medicine, 2014
Ann Int Med. 161 (3): ITC3-1.
 Bedbugs
 Diagnose primarily by history & physical + if mites in home
 Test for hypersensitivity: intradermal allergy skin testing
 Inspect home with magnifying glass and flashlight
 Monitor passively (adhesives, lubricants, bowls)
 Monitor actively: chemical attractants or heat
 Trained dogs can detect live bedbugs and eggs
 Lice and fleas
 Diagnose based on clinical grounds without added tests
 Examine predisposed sites (scalp, groin) for lice
 Examine seams of clothing to identify body lice
 Fleas may be found on pets but not generally on humans
© Copyright Annals of Internal Medicine, 2014
Ann Int Med. 161 (3): ITC3-1.
What are the clinical symptoms and signs
of infestations with cutaneous parasites?
 Scabies
 Pruritus, burrows, excoriations
 Develop 3-4 wk after exposure (1-2 d after reexposure)
 Worse at night and may be worse on genital skin
 Crusted scabies
 Pruritus may be mild or absent due to impaired host
immune response
 Lesions and pruritus resolve within 4 wk after treatment
 Investigate alternate causes if pruritus persists
continued…
© Copyright Annals of Internal Medicine, 2014
Ann Int Med. 161 (3): ITC3-1.
 Bedbugs
 Most patients bitten are asymptomatic
 Small, itchy, red bumps on skin not covered by bedclothes
 After multiple exposures, hypersensitivity may be immediate
 Lice
 Pruritus and excoriated erythematous papules
 Secondary skin infections may occur in excoriated skin
 Head lice: Cervical lymphadenopathy may occur
 Fleas
 Sudden multiple pruritic papules with hemorrhagic crusts
 Bumps often arranged in groups of three
 Hypersensitivity reactions may resemble hives
 Bullous reactions may suggest hematopoietic neoplasia
© Copyright Annals of Internal Medicine, 2014
Ann Int Med. 161 (3): ITC3-1.
What are the usual physical findings in
infestations?
 Scabies
 Diffuse eruption of small pink papules, with burrows,
domed 2- to 3-mm papules, and linear excoriations
 Crusted scabies
 Thickly scaled, erythematous plaques (gritty, sand-like)
 Often misdiagnosed as papulosquamous skin disease
 Bedbugs
 2- to 5-mm erythematous, often excoriated papules
 Bites in linear clusters of ≥3 lesions
 Increased size, itching, vesiculation with repeated bites
continued…
© Copyright Annals of Internal Medicine, 2014
Ann Int Med. 161 (3): ITC3-1.
 Body Lice
 Evidence of eggs or live lice on clothing
 Prefer warmer areas of body (waistband, clothing seams)
 Pubic Lice
 Minute, whitish concretions on pubic hairs shafts
 Perifollicular erythema and firm erythematous nodules
 Inguinal lymphadenopathy may be present
 Rarely: blue-gray macules (thighs, buttocks, anogenital)
 Eyelash infestation: conjunctivitis and crusting and edema
 Examine all body parts once infestation determined
 Fleas
 Papules with central umbilication and hemorrhagic crusts,
often in groups of 3 on ankles and other unclothed areas
© Copyright Annals of Internal Medicine, 2014
Ann Int Med. 161 (3): ITC3-1.
Are there serious complications of infestations?
 Scabies
 Secondary bacterial infections (Staph aureus, Strep
pyogenes)
 Risk: subsequent acute poststrep glomerulonephritis
 Crusted scabies
 Secondary sepsis, with high risk for mortality
 Bedbugs
 Rare systemic reaction (asthma, urticaria, anaphylaxis)
 Secondary infection of excoriations may result in folliculitis,
impetigo, cellulitis, or eczematous dermatitis
 Psychosocial (stress, anxiety, depression, insomnia)
continued…
© Copyright Annals of Internal Medicine, 2014
Ann Int Med. 161 (3): ITC3-1.
 Head Lice
 Severe head lice: iron-deficiency anemia
 Rare allergic reactions (rhinitis and asthma)
 Atypical manifestation: focal alopecia
 Body lice
 Associated with several infections
 Pubic lice
 On eyes: blepharitis, conjunctivitis, corneal epithelial keratitis
 Fleas
 Papular urticaria, psychological distress, phobias, insomnia
 Cat fleas: cat scratch disease, bacillary angiomatosis,
endemic (murine) typhus, rickettsiosis
 Rat fleas: plague, endemic (murine) typhus
© Copyright Annals of Internal Medicine, 2014
Ann Int Med. 161 (3): ITC3-1.
What bacterial organisms do the organisms
transmit?
 Bedbugs
 No evidence able to acquire, maintain, transmit infection
 Lice
 Not considered important vector in bacterial transmission
 Body lice: Borrelia recurrentis and Bartonella quintana
 Fleas
 Bartonella henselae: cat scratch disease, bacillary
angiomatosis
 Rickettsia: endemic (murine) typhus, rickettsiosis
 Y. pestis: plague, which can lead to sepsis and
disseminated intravascular coagulation
© Copyright Annals of Internal Medicine, 2014
Ann Int Med. 161 (3): ITC3-1.
When should a dermatologist or infectious
disease specialist be consulted?
 Dermatologist
 Consider if there’s a high index of suspicion
 Possible inpatient scabies outbreak merits inpatient
consultation
© Copyright Annals of Internal Medicine, 2014
Ann Int Med. 161 (3): ITC3-1.
CLINICAL BOTTOM LINE: Diagnosis...
 Scabies: infestation frequently suspected but often not
clinically confirmed appropriately
 History and physical exam may be sufficiently suggestive
 For suspicious lesions, attempt microscopic exam with
scraping of burrows + mineral oil on glass slide
 Skin biopsy may capture scabies mite (low sensitivity)
 Bedbugs: best confirmed via professional inspection in home
 Flea bites & infestations: hard to confirm w/o home inspection
 Lice: visible to the naked eye
 Adherent whitish concretions on hair shafts
 Refer to dermatologist when suspected diagnosis doesn’t
respond to empiric therapy or follow expected clinical course
© Copyright Annals of Internal Medicine, 2014
Ann Int Med. 161 (3): ITC3-1.
What topical and other therapies are used to
treat cutaneous parasites? What are the
potential toxicities of such treatment?
 Scabies
 Topical permethrin 5%
 Alternative: off-label oral ivermectin
 Lindane 1% use limited by associated neurotoxicity
 Crusted scabies
 Topical permethrin 5% and oral ivermectin
 Alternative: off-label benzyl benzoate 25%
 Monitor rigorously for infection and sepsis
continued…
© Copyright Annals of Internal Medicine, 2014
Ann Int Med. 161 (3): ITC3-1.
 Bedbugs
 Use insecticides to prevent and control infestation
 Pruritic lesions: use intermediate potency topical
corticosteroids or topical antipruritic agents
 Head lice
 Shaving is safe and effective treatment
 Manual wet-combing may be effective if consistent
 Louse-Buster hair drier kills lice by desiccation
 Topical permethrin (1% or 5%), malathion, lindane,
carbaryl, benzyl alcohol 5%
 Topical spinosad 0.9%: kills both lice and their ova
 Oral ivermectin, albendazole, sulfamethoxazole /
trimethoprim, levamisole
continued…
© Copyright Annals of Internal Medicine, 2014
Ann Int Med. 161 (3): ITC3-1.
 Body lice
 Wash clothing and bedding in hot water; high-heat dryer
 Same topical and oral therapeutic options as for head lice
 Pubic lice
 Focal infestation: shaving is safe and effective treatment
 Topical and systemic treatments are helpful
 Treatment of sexual contacts is also recommended
 Eyelashes: ophthalmic-grade petrolatum
 Fleas
 Oral antihistamines and topical corticosteroids for bites
 Remove infestation source: treat pets, prevent contact with
feral animals
 Severe infestations: aerosol insecticide or fogging of
affected areas in the home
© Copyright Annals of Internal Medicine, 2014
Ann Int Med. 161 (3): ITC3-1.
Are there specific safety concerns when
treating pregnant women and children?
 Scabies
 Infants <2 mos: use topical crotamiton 10% or topical
sulfur 8%–10% (in petrolatum)
 Pregnant women and children >2 months: permethrin ok
 Sulfur in petrolatum may be safe alternative in pregnancy
 Oral ivermectin contraindicated for:
 Patients <5 y and <15 kg
 Patients who are pregnant (pregnancy category C)
 Lindane contraindicated for:
 Children <3 y
 During pregnancy (category C)
continued…
© Copyright Annals of Internal Medicine, 2014
Ann Int Med. 161 (3): ITC3-1.
 Bedbugs
 Pregnant women and children: small amounts of mild- to
mod-strength topical corticosteroids safest if needed
 Most topical corticosteroids are pregnancy category C
 Lice
 Mechanical removal safest (shaving, manual wet combing)
 Pregnant/lactating women, children >2 mo: permethrin ok
 Children >4 mo and pregnant women: spinosad ok
 Infants <2 mo: use precipitated sulfur in petrolatum
 Malathion contraindicated during lactation
 Oral ivermectin contraindicated in pregnant or lactating
women and children <5 y
© Copyright Annals of Internal Medicine, 2014
Ann Int Med. 161 (3): ITC3-1.
CLINICAL BOTTOM LINE: Treatment...
 Topical permethrin effective for scabies and lice
 Spinosad is a good alternative for lice in those >4 mo
 Precipitated sulfur in petrolatum is also a safe alternative
 Oral ivermectin effective for scabies and lice but shouldn’t be
given to pregnant women or children <5
 Shaving effective for lice
 Prevent bedbugs and fleas by targeting the reservoirs where
the parasites may be residing
© Copyright Annals of Internal Medicine, 2014
Ann Int Med. 161 (3): ITC3-1.
How can cutaneous parasites be prevented
in the individual patient?
 Scabies
 Treat close contacts with topical permethrin 5% or oral ivermectin
 Providing education and minimizing overcrowding can also help
 Bedbugs
 Prevention = avoidance (no repellants fully prevent infestation)
 Risks: sleeping in unfamiliar environments, buying used furniture
 Lice
 Hot wash & dry: bedding, towels, clothing close hair
 Screen close contacts and treat if active infestation found
 Body lice: Practice personal hygiene, minimize overcrowding
 Pubic lice: avoid sexual contact, sharing bed with infested person
 Fleas: Use mechanical removal or anti-flea products on pets
© Copyright Annals of Internal Medicine, 2014
Ann Int Med. 161 (3): ITC3-1.
What environmental measures can be
taken to prevent cutaneous parasites?
 Scabies
 Hot-water and hot dryer for bedding, clothing
 Alternative: dry clean, store in sealed plastic bags several
days
 Disinfect other exposed objects and surfaces
 Bedbugs
 Consult professional exterminator
 Use chemical and nonchemical (vacuuming, heat/steam,
mattress encasements, discarding furniture) measures
 Reevaluate 10 d to 21 d after treatment
 May spread in ventilation ducts, walls, suitcases
continued…
© Copyright Annals of Internal Medicine, 2014
Ann Int Med. 161 (3): ITC3-1.
 Lice
 Wash clothing and bedding in hot water + hot dryer cycle
 Alternatives: dry cleaning or sealing clothing and bedding
for 2 wk
 Segregate or discard affected hair care items
 Fleas
 Maintain distance between pets and humans
 Groom pets regularly
 Treat infested pet with veterinary topical medications
 Disinfect surfaces, fabrics, carpets with organophosphates
 Prevent feral animals from taking up residence in a home
© Copyright Annals of Internal Medicine, 2014
Ann Int Med. 161 (3): ITC3-1.
What infection control measures for
cutaneous parasites need to be taken in
hospitals and long-term care facilities?
 Scabies
 Some studies: isolate patients with scabies
 CDC: isolate only patients with crusted scabies
 Use heightened surveillance to detect new cases
 Wash hands + avoid skin-to-skin contact with patients
 Provide treatment to patients + exposed contacts
 If refractory: treat all residents & staff with topical benzyl
benzoate or oral ivermectin
 Wash linens in hot water dry with high heat
continued…
© Copyright Annals of Internal Medicine, 2014
Ann Int Med. 161 (3): ITC3-1.
 Crusted scabies
 Routinely clean and vacuum room
 Don’t use insecticide sprays or fumigants
 Bedbugs
 Practice avoidance and prompt treatment of infested areas
© Copyright Annals of Internal Medicine, 2014
Ann Int Med. 161 (3): ITC3-1.
CLINICAL BOTTOM LINE: Prevention…
 Scabies: treat close contacts and minimize overcrowding
 Wash all contacted bedding and clothing with high heat
 Bedbugs: avoid and beware risk in unfamiliar environments
 Head lice: Wash items in close contact with hair
 Treat infestations among close contacts
 Body lice: Practice personal hygiene, minimize overcrowding
 Pubic lice: notify sexual contacts, screen for other STDs
 Avoid sexual contact, sharing bed with infested person
 Fleas: Use anti-flea products + mechanical removal on pets
© Copyright Annals of Internal Medicine, 2014
Ann Int Med. 161 (3): ITC3-1.