Scabies and Lice

Question 1

Define scabies

Answer 1

Skin infestation by a parasitic burrowing mite, Sarcoptes scabei, that is usually spread by skin to skin contact

Question 2

What populations is scabies common in? What are the risk factors?

Answer 2

Common in children, young adults and elderly

Risk factors:

• Poverty and overcrowding
• Institutional care, such as rest homes, hospitals, prisons
• Refugee camps
• Individuals with immune deficiency or that are immune suppressed
• Low rates of identification and proper treatment of the disease

Question 3

What is the 7 year itch?

Answer 3

Chronic undiagnosed scabies

*Note: it is easily missed - should be considered in any patient of any age with persistent generalized pruritus

Question 4

Scabies spread

Answer 4

• quick infestation (holding a child’s hand), can be sexually transmitted and can be spread via bedding (hotels common)
• 3-4 weeks from initial exposure to develop symptoms

Question 5

What is the reproductive cycle of scabies mites?

Answer 5

Male mites die after impregnating females –> females lay ~3 eggs a day that take 10-14 days to hatch –> females life span is 1 month

Question 6

Scabies clinical exam

Answer 6

• Wide range of clinical responses
• Excoriations and eczematous dermatitis that favors the interdigital webs, sides of fingers, volar aspects of the wrists and lateral palms, elbows, axillae, scrotum, penis, labia, and areolae in women
• Head and neck are usually spared

Question 7

How does scabies appear on the skin?

Answer 7

• Burrows appear as 0.5–1.5 cm grey irregular tracks in the web spaces between the fingers, on the palms and wrists.
• Thin thread-like linear “tunnel”
• Excoriations causing erosions are common and can destroy burrows
• Vesicles may also be present
• Red itchy nodules to penis, scrotum are scabies till proven otherwise

Question 8

Complication of scabies

Answer 8

Often impetiginized with staph or strep bacteria from repeated scratching

Question 9

Define crusted scabies

Answer 9

• previously called ‘Norwegian scabies’
• a very contagious variant of scabies in which an individual is infested by thousands or millions of mites living in the surface of the skin.

Question 10

Tx/dx of crusted scabies

Answer 10

• difficult to treat due to extent of infestation (common to become repeatedly infested due to living conditions)
• sometimes requires a biopsy due to significant crusting and thickening of the skin

Question 11

Dx of scabies

Answer 11

• definitive diagnosis when mites, eggs, egg casings or feces are found from the burrows or vesicles and is identified microscopically
• usually diagnosed clinically based on history and exam – solidified by response to tx.

Question 12

When should you consider scabies?

Answer 12

• itchy, red, rash unresolved or unaffected by prednisone is scabies till proven otherwise
• itchy, red, rash starting in finger/toe webs, wrists, waist band, genitalia, consider scabies

Question 13

Tx of scabies

Answer 13

• *No OTC meds are approved for scabies treatment
• 5% permethrin (elimite) is treatment of choice (unless under 2 months old)
• ivermectin 200mcg/kg on day one, then repeat in 1 week: not FDA approved
• 5–10% Precipitated sulphur ointment if allergic to above or if < 2 mo
• Crotamiton cream/lot 10% (Eurax): not FDA-approved for children
• Lindane lot 1% - not recommended 1st line: overuse or accidental swallowing can be toxic to nervous system

Question 14

Patient education regarding tx of home and body after scabies

Answer 14

• Clean bedding in hot water, vacuum carpeting/furniture on treatment days
• Will have post-scabetic pruritus (this is from feces and can last 2 months)

Question 15

Tx of residual scabies pruritus

Answer 15

antihistamines:

• Hydroxyzine HS, Benadryl HS, daily Zyrtec or Claritin
• Topical steroid cream/lot

Question 16

Define pediculosis

Answer 16

This is infestation with lice (plural, louse is singular)

Question 17

How are lice transmitted?

Answer 17

close personal contact or contact with contaminated combs, hats, pillows, clothing, and bed linen

Question 18

What are lice?

Answer 18

• small insects that live on human hair and clothing and can be seen with the naked eye.
• often they are well-camouflaged and reflect the color of the surroundings.
• lice are ectoparasites, meaning they live ‘on’ rather than ‘in’ a host

Question 19

Biology of lice

Answer 19

• Lice are (< 2 mm in size) wingless and have six legs on which are attached strong claws that they use to grasp on tightly to hair shafts or clothing fibers.
• Their piercing mouthparts puncture the skin to feed on human blood.
• Lice can survive for up to 10 days without feeding if they become detached from their human host.

Question 20

Biology of lice continued

Answer 20

• Lice feed approximately 5x daily and do so by piercing the skin with their claws and injecting irritating saliva and then sucking the human’s blood
• The saliva induces pruritus
• Life cycle from egg to egg is one month
• -Egg incubates 8-10 days
• -Maturity is day 18

Question 21

Which species of lice infects the head?

Answer 21

Pediculus humanus capitis

Question 22

Which species of lice infects the body?

Answer 22

Pediculus humanus corporis

Question 23

Which species of lice infects the pubic region?

Answer 23

Pthirus pubis

AKA crabs :)

Question 24

Etiology of pediculosis capitits

Answer 24

• Usually occurs in children, uncommon in adults
• Lice about the size of sesame seed.
• Girls > boys
• Most commonly involves back of head, neck and behind the ears
• African-American children are less commonly affected, perhaps because their hair shape or texture creates a less amenable environment

Question 25

S/sx seen with pediculosis capitis

Answer 25

• pruritis with papular urticaria &/or excoriations esp on nape of neck
• scratching causes secondary bacterial infection
• avg incubation before sxs 4-6 weeks
• *posterior cervical adenopathy without obvious disease is characteristic and should strongly suggest this disease

Question 26

Differentiating between pediculosis capitis and dandruff

Answer 26

• Egg capsules, nits, cemented to hairshaft - very difficult to as opposed to dandruff which is easily removed
• Nits within 1 cm of scalp- confirmation active infestation

Question 27

Etiology of pediculosis corporis

Answer 27

-lice are slightly larger than head louse but looks similar
-is a disease of the unclean so in the homeless, addicts and alcoholics
uncommon**
-vector for spread of systemic illnesses - typhus, relapsing fever and trench fever
-these lice live in clothing and return to skin surface only to feed-so are only rarely seen
-bite reaction, excoriations and secondary bacterial infections.

Question 28

Etiology of pediculosis pubis

Answer 28

• a sexually transmitted disease
• very common problem
• no sexual or racial differences
• chance of acquiring lice from a single exposure is 90% as opposed to syphilis which is 30%**
• smaller and wider than head lice and resembles tiny crab

Question 29

Location of pediculosis pubis on the body

Answer 29

• MC located on pubic hair, but may spread to involve anal area
• in hairy subjects, may spread to thighs, abdomen, axillae, chest and beard

Question 30

S/sx of pediculosis pubis

Answer 30

• Majority complain of pruritus and half of these have no or little inflammation-so pruritus without rash is characteristic
• May have red papules and wheals from bite reaction
• 30% of adults infected with lice will also have another STD

Question 31

Environmental treatment for head lice

Answer 31

• Clean bedding in hot water (at least 130 deg F)
• Vacuum furniture
• Place unwashable items in plastic bag x 2 weeks

Question 32

Treatment of body lice

Answer 32

• Improvement of personal hygiene
• Regular (at least weekly) change of clean clothes
• Clothing, bedding, and towels laundered using water at least 130 degrees F and dried using hot cycle
• Usually pediculicide not needed but if so, follow head lice recommendations

Question 33

Treatment of pubic lice

Answer 33

• OTC 1% permethrin or a mousse containing pyrethrins and piperonyl butoxide
• Lindane shampoo not first-line
• RX Malathion lot 0.5% (Ovide) – not FDA approved for pubic lice
• RX topical or oral Ivermectin – but only topical is FDA approved for lice