Pruritic Infestations

Question 1

Pediculus

Answer 1

Pruritic Infestations
• 6 legs, no wings, ~size sesame seed
• visible oval eggs= *nits      
   - scalp and pubic forms more often see nits and nymph shells than lice
   - body form see nits and lice in clothing seams
• **itching primary symptom
• lower income, military, schools
      - poor hygiene, infrequent change of clothes, crowded
3 forms in humans:
• pediculosis capitis (head lice)
• pediculosis pubis (pubic)
• pediculosis corporis (body)
Treatment pediculosis
• insecticide shampoos or rinses
• nit-comb
• if secondary infection topical antimicrobial
• clean headwear, towels, bedding

Question 2

Pediculosis capitis

Answer 2

Pruritic Infestations
• adult louse white or grey
• nits yellow to white, firmly attached to hair base
PATH
- eggs hatch to release nymph→dull yellow nymph shell remains attached, more visible than adults→itching→secondary bacterial infection→ skin red, excoriated→ crusty, foul-smelling ‘cap’
- *regional lymphadenopathy common

Question 3

Pediculosis pubis

Answer 3

Pruritic Infestations
• Phthirus pubis
• **‘crab-like’
• usually STI
• intense itching→ eczematization= ‘vagabond’s disease’
• can also attach to hair on other body parts
- Pubic lice are generally spread through sexual contact and may be used as a marker of other sexually transmitted infections
- *Head lice are common in urban areas and spread easily because infected individuals are reluctant to share information w/ contacts owing to the social stigma associated w/ infestation
- *DNA extracted from pubic lice in victims of rape has been used to help identify perpetrators. Lice found on the eyelashes are typically pubic lice rather than head lice

Question 4

Pediculosis corporis

Answer 4

Pruritic Infestations
• feeds on skin but doesn’t remain attached
   • *prefers seams of clothing
• also transmits:
   • epidemic typhus
      • Rickettsia prowazekii
   • trench fever, bacillary angiomatosis, endocarditis
      • Bartonella quintana
   • louse-born relapsing fever
      • Borrelia recurrentis
TX
• insecticide cream
• *clean clothing
   – *HOT WATER, DRYER

Question 5

Sarcoptes scabiei var. hominis

Answer 5

Pruritic Infestations
• 8 legs
• adult mites 0.3-0.4 mm long
• *scabies most common infestation worldwide
• *poverty, overcrowding, poor hygiene
PATHOGENESIS
- female mite *burrows through *stratum corneum (proteases)→lays eggs (2-3/day)→few days larvae hatch→**intense itching →possible widespread *papular rash (immune response w/ multiple excoriation marks→possible secondary bacterial infection
DIAGNOSIS 
• burrows esp. finger webs, finger sides, wrists, hand sides
- linear, palpable ridges w/ black speck→ mite
• tease out w/ needle→ microscope
• if not, burrow scrapings→ microscope
TX
• insecticide cream (permethrin)
• clean bedding, towels, clothing
• close contacts, sexual partners

Question 6

Norwegian scabies=crusted= hyperkeratotic

Answer 6

Pruritic Infestations
• widespread crusted eruption, may not be itchy
• *huge ↑ # mites and eggs
• *very contagious
• direct contact, fomites
• immunocompromised, elderly, disabled, debilitated
• **permethrin + oral ivermectin + keratolytic agents for improved penetration of scabicides through hyperkeratotic crusts