Parasitic Infections

Question 1

Pediculosis

Answer 1

Lice!
- Belong to order Anoplura (sucking lice)
o Sucking mouthparts penetrate skin & feed on blood
- 1-3 mm flat creatures with 3 pairs of legs. Females lay 300 nits during a lifetime
o Nits are opalescent, found on hair shafts, and hatch in about 1 week

Question 2

what are the 3 forms taht are parasitic to humans?

Answer 2

body, head, and pubic

Question 3

Body louse

Answer 3

Pediculosis humanus corporis

Question 4

Head louse

Answer 4

pediculosus humanus capitus

Question 5

pubic

Answer 5

phthirus pubis

Question 6

how are they transmitted?

Answer 6

P2P

Question 7

Lice CF

Answer 7

pruruitus is variable in severity, excoriations may become secondarily infxn
o Classic: small erythematous papules (papular urticaria)
Axillae, neck, shoulders
Hemorrhagic puncta and linear excoriations also common (former represent intradermal hemorrhage at site of bite)
nits may be seen on hair shaft

Question 8

maculae caerulaea

Answer 8

bluish-brown or gray macules at site of bite, may be heme breakdown product

Question 9

first line tx of lice

Answer 9

prevention is key
Permethrin
pyrethrins
malathion
*** Need to reapply in 7-10 days to kill any newly hatched lice

vasaline can be used to suffocate lice

Question 10

alternative tx of lice

Answer 10

lindane or ivermectin

Question 11

scabies

Answer 11

• Sarcoptes scabiei – an 8-legged mite

- can live as long as 48 hours on clothing bedding and furniture

Question 12

scabies CF

Answer 12

• Itching, scabs, burrows – intensely pruritic rash that is usually worse at night
  o Excoriations and crusting
• Infants get nodular eruption, including head

Question 13

scabies pathogenesis

Answer 13

hypersensitivity (immediate and delayed. normal incubation period is 21 days for first infestation

Question 14

scabies dx

Answer 14

• Lesions  tunnels (0.5-1 cm); excoriated papules & pustules
• Sites of predilection  finger webs, flexor aspects of wrist, elbows, axillae, penis, external genitalia, feet & ankles
  o Most commonly distributed on the hands, genitalia, and axillary areas
• Clinical diagnosis… look for burrows. Place mineral oil over burrows and scrape off with a #15 blade, then examine under microscope and look for mites

Question 15

what are most secondary infections caused by in scabies?

Answer 15

GAS

Question 16

scabie tx

Answer 16

1 %5 permethrin

Question 17

alternate scabies tx

Answer 17

1% lidocane

ARD: neurotoxicity, avoid in those <2 o, extensive dermatitis, and preg/lactating

Question 18

how does scabe tx work?

Answer 18

apply to skin and leave on overnight (8 hours) was off in am. repeatt in 7 days

Question 19

clinical pearls for scabies

Answer 19

humans can be infested by mites of dogs, (self-limiting, no tx) wash bedding, clohtes in hot water

Question 20

spider bite

Answer 20

brown recluse (Laxaxceles reclusa)

black widow

Question 21

progression of a spider bite

Answer 21

pain 3 hrs after bite, systemic sx begin 4-6 hours, the acute necrotic injury to skin (lasts 10-15 days)

Question 22

what can black widows cause?

Answer 22

neurologic overstimuation (muscle aches, spasms, rigidity)

Question 23

brown recluse rxn

Answer 23

red, white and blue

1) infarct of skin caused by rapid blood coagulation w/in vessles
2) leion is sinking macule, pale grey in color, slightly eroded in cener, halo of tender inflammation and hemorrhage
* can often extend into muscle

Question 24

tx of spider bites

Answer 24

mostly mananged wtih local care and analgesics

antivenom is rarely indicated

Question 25

tx of black widow bites?

Answer 25

diazepam and calcium gluconate