Parasitic Skin Infections Flashcards
What are parasitic dermatoses?
pediculosis and scabies
What causes pediculosis?
ectoparasites that live on body
What is the common term for pediculosis?
lice
What causes the pruritis with lice?
pierce skin and inject saliva
Are lice able to survive away from human host?
yes
How long does it take for lice to die of starvation?
10 days away from host
How many eggs does a female louse lay each day?
3-6, white 1mm long
How long does it take a nit to latch and mature?
8-10 days hatch, 12-15 mature, live for 10 days
What lice infest head?
Pediculosis capitis
What lice infest body?
Pediculosis corporis
What lice infect pubic area?
Pediculosis pubis or Pthirus pubis
What is the most common manifestation of pediculosis?
pruritis
Where does p corporis cause itching?
axilla, truncal and groin
What are associated features of pediculosis?
papules, wheals, bit reaction, excoriation
What is pathognomic for infestation of life?
maculae cerulea
How do maculae cerulea?
blue-gray macules, enzyme in saliva break down human bilirubin
How long does head lice survive away from human?
1-2 days
What are the effected areas in pediculosis capitus?
scalp, neck, postauricular
How do you get head lice?
combs, brushes, hats, scarves, bedding
How do you dislodge lice?
sweater removal, hair combing
How far can head lice travel?
23 cm/min
What are symptoms of p. capitis?
scalp pruritius, occipital lymphadenopathy, impetigo
Where is heaviest infection for p. capitis?
retroauricular scalp
Where do p. corporis lay their eggs?
clothing fibers
How long can p. corporis survive?
10 days
What has p humanus corporis?
typhus, trench fever, relapsing fever
What do you see with p. corporis?
multiple lesions from bites present, uninfected are papules 2-4 mm, located anywhere
What are eyelash nits a manifestation?
pubic louse infestation
What lice species is less mobile?
p. pubis
How long can p pubis survive off human?
1 day
What are the medical treatments for head lice?
permethrin topical melathion topical Invermectin Lindane topical Benzyl alcohol Spinosad topical
What is permethrin topical?
Apply lotion once, can repeat in 7-9 days
First line therapy, although some resistance has developed
Must also use fine-toothed comb to remove nits
Indicated in adults and children over 2 months of age
What is malathion topical?
Apply once, repeat in 7-9 days
Binds to hair for longer lasting effect
Indicated in adults and children over 6 years of age
What is invermectin topical?
Apply once, no combing needed
Indicated in adults and children over 6 months of age
What is lindane topical?
Apply apply 30mL of shampoo once
Do not apply on open wounds
Not safe for use in children, due to transcutaneous absorption/neurotoxicity
although still FDA approved down to 1 month of age
What is benzyl alcohol?
Apply to hair once, then repeat in 7 days
Dosing based on hair length (varies 4oz to 48 oz)
Indicated in adults and children
What is spinosad topical?
Apply once (maximum 120mL), repeat in 7 days Indicated in adults and children over 4 years old
What is the treatment for pubic lice?
Permethrin topical (1% lotion) Malathion topical (0.5% lotion) Lindane topical (1% shampoo) – 30mL repeated in 7-10 days
How do you treat eyelash infestations?
petrolatum ointment
How do you treat body lice?
clean clothes and bed linens, educate about hygiene
Permethrin spray on clothes
Oral ivermectin 12 mg 3 doses 7 days apart - heavy pediculosis
What is the environmental treatment of head lice?
treat fomites launder everything temp 131 for 5 min Place in dryer high heat 30 m in seal in plastic bag 2 weeks vacuuming discard combs and hairbrushes or soak in hot water 5 min
What is intensely pruritic skin infestation caused by host specific mite?
scabies
What causes scabies?
sarcoptes scabiei hominis
What is the pathognomic sign for scabies?
burrow - intreepidermal tunnel by moving female mites
serpiginous grayish threadlike elevations in superficial dermis
2-10 mm long
Where does scabies occur in geriatric?
back, appear as excoriation
Where do you see scabies in infants and small children?
palms and soles
Where are high yield locations for scabies?
Webbed spaces of the fingers Flexor surfaces of the wrists Elbows Axillae Belt line Feet Scrotum (men) Areolae (women)
How does scabies look?
vesicles are discrete lesions filled with clear fluid, although the fluid may appear cloudy if the vesicle is more than a few days old
What is crusted scabies?
lesions are hyperkeratotic and crusted
Cover large areas
Marked scaling is common
Pruritus may be minimal or absent
Nail dystrophy and scalp lesions may be prominent
Hands and arms are the usual locations for lesions
Mites can number in the thousands to millions in this form of scabies
What is nodular scabies?
Nodules occur in 7-10% of patients with scabies
young children (neonates unable to scratch)
pinkish brown nodules
ranging in size from 2-20 mm in diameter
What are scabies agents?
Permethrin or ivermectin (1st line)
Malathion or benzyl benzoate (2nd line)
Lindane (3rd line)
What is special about scabies and preg?
only treat if benefit exceeds risk and + skin scraping
Who is premethrin safe to use in?
pregnant and children >2mo
How do you treat neonates with scabies?
precipitated sulfur 6% petroleum
What is the treatment for crusted scabies?
several different medications used sequentially
Typically permethrin OR benzyl benzoate & invermectin
AND keratolytic (urea topical) allows for drug penetration in crusted areas
How do you treat scabetic nodules?
intranodular steroid injections
What does bed bugs cause?
erythematous papules, somtimes with prominent urticarial component
When do bugs come out?
night, 1 hr before dawn
How do you treat bed bugs?
sysmptomatic - steroids or antihistamines
How do you prevent bed bugs?
insecticides and eliminate bedbug hiding spots, permethrin spray can be applied to clothes, prevent bedbugs from gaining access to the bed
