Infestations Flashcards
What organism causes scabies?
Sarcoptes scabies variety hominis
What exam finding is pathognomonic of scabies?
Burrows
Can the scabies hominis live on other animals?
No, the scabies species are host specific, they only live on their natural host
How long is the life cycle of the scabies mite in the human skin?
30-day life cycle
- Lives in the stratum corneum only
How long can a scabies mite live off of a human host?
1 week
What are the most commonly affected locations of scabies?
Classically affects interdigital web spaces, wrists, genitals and trunk. Can cause chronic, reactive inflammatory nodules
In what patients does crusted or Norwegian scabies most often occur?
Immunocompromised host
Treatments for scabies?
Permethrin 5% cream, ivermectin, lindane
What are the 3 varieties of louse?
Head louse, body louse, and pubic louse
What is the name of the organism that causes pediculosis capitis?
Pediculus humanus
What are the most common locations for pediculosis capitis?
Occipital and post auricular areas
How long can head lice live without a blood meal?
Can live for 36 hrs for the organisms. Nits are strongly adherent to hair and can survive 10 days
What organism causes body lice?
Pediculus humanus corporis
What diseases can be spread by body lice?
epidemic typhus (R. prowazekii), louse-borne relapsing fever (B. recurrentis), and trench fever (B. quintana)
Where do the body lice live and lay eggs usually?
Live and lay eggs on clothing
What organism causes pubic lice?
Pthirus pubis
How are pubic lice different looking from other lice?
They are short broader body and have 4 frontal crab-like appendages
What are the blue-gray macules seen in pubic areas or trunk from pubic lice called?
Maculae ceruleae
How do you treat pubic louse?
Permethrin 1% pyrethrins or malathion (flammable, only for age >2 years old)
What organism causes burrowing flea?
Tunga pernetrans
How does tungiasis occur?
Female organism burrows head-first into the skin, usually on feet or toes and extrudes eggs from punctum before dying and being sloughed off with epidermis.
In what areas is tungiasis common?
Caribbean, Central/South America, and sub-Saharan Africa
Treatment for tungiasis?
Surgical removal or ivermectin. Patients also need to have tetanus prophylaxis
What organisms can cause myiasis?
Dermatobia hominis (human botfly) is the most common. Is transmitted by mosquito
Tumbu (Cordylobia anthropophaga) is another one, larva are deposited on damp clothing and penetrate skin when clothes are worn
What is wound myiasis?
Caused by organisms (Cochliomyia hominivorax, Chrysomyia bezziana) cannot penetrate intact skin; once laid within open wound, they penetrate subcutaneous structures and can even go into cartilage and bone (can penetrate cranium if by nose)
Treatment of myiasis?
Surgical removal, antibx for secondary infxn
