Ectoparasites (Diemert) Flashcards
Name two infestations with parasites that live on or in the skin (common to US)
Scabies (sarcoptes scabiei) and pediculoses (lice)
Name three infestations with parasites that live on or in the skin (seen in travelors)
Tungiasis, myiasis, cutaneous larva migrans
Common characteristics of ectoparasites
do not cause significant disease, higher prevalence in vulnerable groups, elicit strong inflammatory and immune response (not protective)
Sarcoptes scabiei transmission
person-to-person; fomites (towels, clothes); sexually transmitted
Sarcoptes scabiei mechanism (eggs and immune response)
- female burrows into dermis and lays eggs; hatch in 3-4 days
- Type IV hypersensitivity reaction to MITES AND EGGS
Sarcoptes scabiei clinical manifestation
- intense pruritus 3-4 weeks (sooner after re-infestation)
- erythematous papular, vesicular, pustular lesions
- short, serpiginous burros (2-3 mm) in hands, feet, wrist, waistline, genitals
Sarcoptes scabiei diagnosis
- microscopic exam of skin scrapings
- burrow ink-test
Sarcoptes scabiei treatment
- topical permethrin cream (treat 2x 1 week apart because eggs hatching); treat entire house and sexual contacts; apply to whole bodt
- oral: ivermectin (single oral dose, repeat after 1 week)
- wash linens with hot water
What is crusted or Norwegian scabies?
- affects immunocompromised (HIV, HTLV, alcoholic)
- affects entire dermis
- hypertrophic rxn
- NOT pruritic (less inflam)
What is nodular scabies?
- usually on genitals, axillae, but, areolae
- resolves w/ post-inflamm. hyperpigmentation
Pediculoses (lice) mechanism
- hairy parts of body: female deposit eggs/nits on emerging hair shaft (nits hatch after 6-10; resulting nypmh develop into adults in 10 days; adults live for 1-3 months)
- feed on human blood; dies within 24 hours w/o host
Pediculoses capitis (head lice) clinical
-pruritus: hypersensitivity to feeding adult lice saliva
secondary bacterial infection due to scratching
Pediculoses capitis (head lice)
visualize nits or lice
-Wood’s lamp: live nits fluoresce
Pediculoses capitis treatment
topical pediculocides
- gels, lotions, creams or foams better than shampoos bc longer contact time
- pyrethroids, malathion do not kill nits so need to re-treat after 7-10 days
Pediculoses corporis (body lice) mechanism
- person-to-person transmission
- poor socioeconomic conditions and crowding
- found on clothing (adults attach to skin only to feed)
- vector for epidemic typhus and relapsing fever
Pediculoses corporis clinical and treatment
same as head lice
-pruritus: hypersensitivity to feeding adult lice saliva
(secondary bacterial infection due to scratching)
topical pediculocides
- gels, lotions, creams or foams better than shampoos bc longer contact time
- pyrethroids, malathion do not kill nits so need to re-treat after 7-10 days
Pediculoses pubis (Phthirus pubic; crabs) overview
- nits/adult lice attach to hair
- person-to-person (not prevented by condoms)
- clinical: pruritus
- treatment: topical pediculocides (retreat after 7-10 days); treat sex partners; wash everything
Cimex lectularius (common bedbug) characteristics
- nocturnal (hide in furniture during day)
- blood feeding (bites are in CLUSTERS)
- symptomatic treatment: anti-histamines and topical corticosteroids
- killed by heat but difficult
Tungiasis (Jiggers, chigoes) characteristics
- SAND flea
- epidermis affected
- usually feet, under toenails, webs
- feeds on blood and tissue
- travelors
Tungiasis clinical and mechanism
- papule w/ central black dot marking rear of flea; grows rapidly
- painful, itchy
- 2-21 days after penetration, shiny white eggs extrude
- flea dies after 3-5 weeks after penetration
Tungiasis treatment and complication
- extraction
- secondary bacterial infection
Myiasis (maggots) affected areas of world
-tropics
Myiasis transmission
- tumbu fly in southern Africa (eggs laid on damp linen; larvae hatch and penetrate skin when come into contact)
- botfly in South, Central America (captures mosquito, lays eggs on its abdomen, then gets delivered to human during bite)
Myiasis types
- furuncular: most common, subq
- wound: eggs laid on existing wound
- cavitary: intestinal, urogenital (uncommon)
Myiasis typical lesion (furuncular)
- boil-like, non-healing, erythematous lesions
- ooze when squeezed
- central punctum (may see rear of bug)
- pruritus and pain common (may feel larva moving within lesion)
Myiasis management
- asphyxiate larva (vaseline, nail polish, bacon)
- may need to surgically extract
Myiasis prevention
- mosquito repellent and bed nets (Americans)
- iron all clothing prior to wearing
Myiasis if left untreated…
-larva emerges in 5-10 weeks, drops to ground and pupates
