Infestations (1/31) Flashcards
What is the cause of head lice?
Pediculosis capitus
What is pediculosis capitus like?
Ectoparasite: lives outside the host
3-4 mm, both males and females have mouth parts to feed on human blood, legs equipped to grasp human hairs
They stay close to the scalp for warmth and to feed several times daily
Human is the only host
What are the 3 stages of peidulosis capitus?
Egg “nits”
Nymph
Adult
What are the symptoms of head lice?
Most cases are asymptomatic!
If symptomatic, itching due to allergy to saliva, tickling of something moving in hair, difficulty sleeping bc they are most active in dark, sores that become infected
Excoriations, cervical/nuchal lymphadenopathy, pyoderma on head/neck, fever
How do you diagnose head lice?
Diagnose by finding live lice, use wet-combing technique
Sometimes you might find nits and not lice. If they are within 1/4 inch of scalp, assume they are present and treat
If they are beyond 1/4 inch & no live lice are seen, you can’t make the diagnosis
Nits can be confused for dandruff, root sheath casts, white piedra (fungal), hair spray, dirt. But nits are firmly adherent to the hair shaft
How do head lice spread?
Head to head contact
Sharing brush/comb, headphones
NOT pets
Lice can’t jump or fly
How do we treat lice?
Treat person & check their family members and close contacts
Topicals: You have to re treat after a week, because it does not kill eggs
OTC options: pyrethrins with piperonyl butoxide = neurotoxic to the lice
Permethrin lotion (similar to above)
Malathion lotion (neurotoxic, kills lice and eggs, takes 12 hours)
Benzyl alcohol lotion- asphyxiates the louse, not ovicidal
Topical ivermeticin: paralyzes lice, single 10 min application to dry hair
Resistance varies by geographc region; also you have to wash clothes and bedding in hot water or seal in plastic bag for 2 weeks
What are crabs?
Phthirus pubis = same thing as hair lice = pediculosis pubis
How are crabs transmitted?
Sexual
Through clothes, bedding, towels
No flying or jumping
30% of people with pubic lice have another STI
What are the symptoms of crabs?
Itching, excoriations
Pale bluish macules in response to anticoagulent in saliva
Lymphadenopathy
Superimposed bacterial infection
Live lice
Nits
How do you treat crabs?
Similar to head lice
First choice = permethrin, pyrethrins
Other: malathion, ivermectin, lindane - not first line
What are scabies?
Sarcopetes sabiei: a human mite
Microscopic, whitish brown 8 legged mite
They live in the stratum corneum in skin, they lay eggs here; burrow using proteolytic enzymes that damage keratinocytes
Extremely itchy, grayish serpentine lines, pimple-like rash
You can get scabies from an animal but these infections are self-limited: don’t reproduce in host
10-15 mites at a time only
Where do you get scabies?
Person to person contact, not necessarily sexual
Classic = between fingers and on wrists
What are the symptoms of scabies?
Sever itching, worse at night, due to type iv hypersensitivity reaction to the mite, its eggs, its feces
Starts with a papule, might be crusted, burrows
Secondary bacterial infections
Do a skin scraping, adhesive tape tests - but if negative, don’t exclude scabies
How do you treat scabies?
Permethrin
Oral ivermectin
Treat close contacts, wash items, bag clothes for 3+ days
Symptoms: antihistamines, topical/oral steroids
