Lecture 5: Infestations Flashcards
Where is pediculosis capitis MC and how does it present?
- Lice
- MC in schools, day-cares, SNFs, dorms, prisons
- Intense pruiritis of the scalp
- MC in white school aged girls/mothers
Warmer months
What does a louse look like?
- 1-3 mm long, flattened brownish-gray, 3 pairs of legs and claws
- lifespan 14-18d
- Nits are 1 mm and opalescent (eggs)
Humanus are in clothing, capitus on hair shafts
How to differentiate seborrheic dermatitis, tinea capitis, psocid lice, and psoriasis from pediculosis capitis?
- Seborrheic is yellow, greasy, and easy to remove
- Tinea capitis is more closely associated with alopecia
- Psocid lice are MC in plant debris/wooded areas
- Psoriasis is morphologically distinct
What do lice and nits do to the scalp?
- Mauculae cerulae or purpuritic stains may suggest infestation
- Occipital lymph node involvement
- Microscopy shows an oblong structure attached to hair an an acute angle with a breathing appartus at its superior end
Diagnostic pearls for pediculosis capitis
- Pyoderma + occipital/cervical LAN suggest infestation
- Nits are oval and tenacious; they stay stuck
- Nits fluoresce under Wood’s lamp
Best tests for pediculosis capitis
- Microscope
- Wood’s lamp of nits
Management of pediculosis capitis
- Permethrin has increasing resistance
- Manual combing via fine comb
Should you treat a kid with empty nit cases?
No
Only live lice or eggs
OTC tx for pediculosis capitis
- Permethrin (Nix): dry hair then rinse after 10m. Repeat in 1-2 weeks
- Pyrethrins + piperonyl butoxide(RID, Pronto): same as above
Rx tx for pediculosis capitis
- Spinosad/Natroba: children > 4y First line tx
- Malathion lotion
- Permethrin 5% (off-label)
- Ivermectin lotion: 6 months or older & not preggo
- Oral ivermectin (off-label), don’t use under 5y.
Tx for eyelid involvement of pediculosis capitis
Petrolatum BID for x8d
Organism for pediculosis corporis
Pediculus humanus corporis
Lives in clothing
Presentation of pediculosis corporis
- Pruiritis
- Bites of macules and papules in intertriginous areas
- Maculae cerulea: blue gray macules are pathognomic for lice infestation
- 2-4 mm wingless, blood sucking arthropods.
What is vagabond disease?
Body louse infection that goes on for years, developing parasitic melanoderma = darkened/thickened skin
What is characteristic of bed bug bites?
Linear bite distribution
Bfast, lunch, dinner distribution
Best test for pediculosis corporis
- Physical examination
- Finding a live louse/viable nit = confirmation of dx
- Wood’s lamp will show yellow-green
- Check clothing seams
- Shake clothing and use tape to pick up debris
What are the 3 diseases transmitted by P. humanus corporis?
- Typhus (Rickettsia prowazekii)
- Relapsing fever (Borrelia recurrentis)
- Trench fever (Bartonella quintana)
Mainstay is just eradicating infestation
Tx for pediculosis corporis
- Clothing on hot water and high heat
- Iron furniture
- Heavy infestation: 5% permethrin cream or lotion for 8-14 hrs
Overview of pediculosis pubis
- STD, aka crabs
- Can be spread also by fomites
- Not pet related
- Extremely pruiritic
- Condoms do not stop transmission
Why is pediculosis pubis hard to remove?
- Chitin formation to cement themselves.
- However, can’t live without a host for more than 24h.
Clinical signs of pediculosis pubis
- Erythematous macules or papules present at feeding sites
- Wheals
- Small pinpoint bleeding on intimate clothing
Management pearls for pediculosis pubis
- Notify sexual partners in most recent month
- Concomitant STDs is common
- Sexual contact or fomite can be transmission
- Wash in hot water or store away for 2 weeks in air-sealed bags
- Secondarily infected lesions needs abx
Preferred tx by CDC for pediculosis pubis
- Permethrin 1% (> 2 month olds)
- Mousse with pyrethrins
- After tx, can remove nits with fine comb
How does permethrin work?
- Neurotoxin resulting in respiratory paralysis of parasite
- Body: leave cream overnight and then rinse
- Head lice: leave 10 mins, rinse and comb out.
Both are repeated in another week PRN.
How does pyrethrin/piperonyl butoxide work and its CI?
- Lotion/shampoo
- Pyrethrin is a neurotoxin
- Piperonyl is a synergist
- Cannot be used in < 2 y/o or allergy to ragweed
- Apply to wet areas for 10 mins and rinse.
How does malathion work and its CI?
- Head lice lotion that is Rx only
- Neurotoxic: inhibits cholinesterase
- CI: < 6y
- Leave in dry hair for 8-12 hrs
- It is flammable
Last resort tx for pediculocide therapy
Lindane/Kwell
What does Lindane do and CIs?
- MOA: neurotoxicity causing seizure and death
- BBW: neurotoxicity, so no children, elderly, light wt ppl
- Banned in CA
- Place on before you shower
- Do not use more than once
What causes scabies and MC mode of transmission?
- Mite: Sarcoptes scabiei var. hominis
- MC: Direct contact
fomite spread is rare
Overview of scabies
- 10-20 mites per infestation
- Extremely pruiritic 2-6 weeks later
- Persists without tx!
Presentation of scabies
- Worse at night
- Diagnostic sign: fine, thread-like line with tiny black speck at the end.
- Small, erythematous papules
- Rarely on head or neck
What location on men and women suggests scabies if itchy/papular?
- Women: areola
- Men: Penis and scrotum
Dermoscopy finding for scabies
Jetliner with a trail
Negative prep != lack of scabies
Who is crusted scabies/norwegian scabies MC in?
- Immunocompromised
- Institutionalized
What is crusted scabies like?
Thousands to millions of mites
Tx of crusted scabies
- Topical Permethrin 5% overnight
- +
- Oral ivermectin x5 dosing
Best tests for scabies
- Scabies prep via scraping and microscopy and mineral oil
- Add on KOH for crusted scabies
Management of scabies
- First-line: permethrin 5% or Rid
- Last resort: Lindane (Avoid in crusted)
- Oral ivermectin (2nd line, 0.2mg/kg/d)
Supplies for skin scrapings
- 15 scalpel blade
- Microscope slide
- Slide cover
- Mineral oil or KOH
- Microscope
KOH is for fungal or crusted
Mineral oil is applied prior to scraping for scabies.
Overview of a black widow
- MC widow spider
- Likes woodpiles
- Makes you extremely sick
- Halo-like lesion around bite
- Females have the red hourglass on their abd
Lactrodenus genus
Overview of recluse spiders
- MC in temperature and tropical regions
- Cause local necrosis primarily
- Loxosceles genus
- Can cause DIC
- Brown recluse spider has a violin shaped figure
Main concern is hemolysis i think
Funnel-web spider overview
- Hobo spider: tegenaria agrestis
- PNW
- Neurotoxic venom extremely fatal
Overview of tarantulas
- Theraphosphidae have relatively harmless bites
- Generally cause local skin reactions/allergies
How to find a spider bite
- 2 small puncta fang marks
- Erythema and edema
- Necrotic/dusky center in a red inflammatory plaque
- Brown recluse: vesicles and bullae quickly
- Black widow: Local sweat, piloerection, mild edema
Gold standard for diagnosing a spider bite
Spider collection with positive identification
What should we check if we suspect brown recluse bite?
- Hemolysis
- Order Serial Hgb and plasma-free haptoglobin if hemolysis suspected.
- Rhabdo, renal, DIC
What controversial drug can we give for necrotic lesions due to spider bites within 36 hrs?
Dapsone
