Infestations

Question 1

What organism causes scabies?

Answer 1

Sarcoptes scabies variety hominis

Question 2

What exam finding is pathognomonic of scabies?

Answer 2

Burrows

Question 3

Can the scabies hominis live on other animals?

Answer 3

No, the scabies species are host specific, they only live on their natural host

Question 4

How long is the life cycle of the scabies mite in the human skin?

Answer 4

30-day life cycle

• Lives in the stratum corneum only

Question 5

How long can a scabies mite live off of a human host?

Answer 5

1 week

Question 6

What are the most commonly affected locations of scabies?

Answer 6

Classically affects interdigital web spaces, wrists, genitals and trunk. Can cause chronic, reactive inflammatory nodules

Question 7

In what patients does crusted or Norwegian scabies most often occur?

Answer 7

Immunocompromised host

Question 8

Treatments for scabies?

Answer 8

Permethrin 5% cream, ivermectin, lindane

Question 9

What are the 3 varieties of louse?

Answer 9

Head louse, body louse, and pubic louse

Question 10

What is the name of the organism that causes pediculosis capitis?

Answer 10

Pediculus humanus

Question 11

What are the most common locations for pediculosis capitis?

Answer 11

Occipital and post auricular areas

Question 12

How long can head lice live without a blood meal?

Answer 12

Can live for 36 hrs for the organisms. Nits are strongly adherent to hair and can survive 10 days

Question 13

What organism causes body lice?

Answer 13

Pediculus humanus corporis

Question 14

What diseases can be spread by body lice?

Answer 14

epidemic typhus (R. prowazekii), louse-borne relapsing fever (B. recurrentis), and trench fever (B. quintana)

Question 15

Where do the body lice live and lay eggs usually?

Answer 15

Live and lay eggs on clothing

Question 16

What organism causes pubic lice?

Answer 16

Pthirus pubis

Question 17

How are pubic lice different looking from other lice?

Answer 17

They are short broader body and have 4 frontal crab-like appendages

Question 18

What are the blue-gray macules seen in pubic areas or trunk from pubic lice called?

Answer 18

Maculae ceruleae

Question 19

How do you treat pubic louse?

Answer 19

Permethrin 1% pyrethrins or malathion (flammable, only for age >2 years old)

Question 20

What organism causes burrowing flea?

Answer 20

Tunga pernetrans

Question 21

How does tungiasis occur?

Answer 21

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.

Question 22

In what areas is tungiasis common?

Answer 22

Caribbean, Central/South America, and sub-Saharan Africa

Question 23

Treatment for tungiasis?

Answer 23

Surgical removal or ivermectin. Patients also need to have tetanus prophylaxis

Question 24

What organisms can cause myiasis?

Answer 24

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

Question 25

What is wound myiasis?

Answer 25

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)

Question 26

Treatment of myiasis?

Answer 26

Surgical removal, antibx for secondary infxn