Lice and Scabies Flashcards
(90 cards)
1
Q
What is pediculosis?
A
Aka lice
Ectoparasites (on the outside) that live on human hosts
There are 100s of millions of cases every year world wide
Outbreaks occur in schools, day-care centres and long-term care facilities
2
Q
How common is head lice?
A
In North America, there prevalence is about 1-3%
Annual incidence of 25-35% in primary school children
3
Q
Describe a pediculus humanus capitus
A
They are wingless
They about 1-3 mm long
Usually tan but they will change colour with the hair that they are in (darker hair, darker louse)
They feed on blood and they feed several times a day
They live within an inch (or even 1 cm) of the scalp (they don’t live at the ends of long hair)
4
Q
Describe pediculus humanus corpis
A
Aka body louse
They are a bit bigger than head lice; 2-4 mm
They live and hide in the seams of the clothing
They are the only type of louse that can spread disease
5
Q
Describe phthirus pubis
A
Aka pubic louse
Shorter and more round
Pin-sized head; 0.8-1.2 mm long
Appear yellow-brown, dot-like
Coloquial name: crabs (they resemble the crustacean)
They are more wide spread because pubic hair is a little more spread out
6
Q
Where do pubic lice live?
A
They live in the pubic area, but are sometimes found under the armpits, in the eyelashes, in moustaches, beard and eyebrows
7
Q
Describe of the a head louse
A
Starts as an egg
Nymphs emerge after 6-10 days (first nymph, second nymph, third nymph, adult)
Nymphs must undergo 3 molts over 10 days
The female louse can survive for 1 month and lay between 5–10 eggs per day
8
Q
How long can a louse live off a host? What about an egg?
A
The adult can survive 1-4 days off the host
The eggs can survive off the host for about 10 days
9
Q
What are risk factors for head lice?
A
More prevalent in school-aged children (aged 3-11)
More prevalent in females (longer hair and girls tend to play dress up and share hats and brushes)
It is NOT more prevalent when there’s a lack of hygiene (lice prefer clean hair)
10
Q
What hair type do head lice prefer?
A
Straigh hair
African-american has a curl to it and North American lice find it difficult to graph that type of hair.
In North America, lice is more prevalent in caucasians. In Africa, the lice survive better on the cylindrical hair
11
Q
What are the risk factors for body lice?
A
Poverty
Overcrowding
Low hygiene
12
Q
What are the risk factors for pubic lice?
A
If a person is sexually active (females 15-19 years, males 20 years)
More prevalent in young adults
Hygiene is not a factor
13
Q
How is head lice transmitted?
A
Head to head contact or by fomites (hats, hair accessories, brushes, towels)
Lice are very quick; head to head contact take about 30 seconds
14
Q
How is body lice transmitted?
A
Direct body contact with infested person
Shared clothing and linens
15
Q
How is pubic lice transmitted?
A
Mainly sexual or close body contact
Possibly fomites
16
Q
Do pets increase the risk of lice?
A
No, lice only live on humans
17
Q
What are the signs and symptoms of head lice?
A
Itching on the back of the head and near the ears
There are sometimes bite marks (less common)
The pillow case might have thin brown lines (fecal waste)
1/3 of kids will be asymptomatic
18
Q
What causes the itching in head lice?
A
When the lice bite the scalp, they inject vasodilatory and anticoagulant properties that people will develop hypersensitivity (takes 2-6 weeks for development after first exposure; second exposure will take 1-2 days)
19
Q
Describe nits
A
Aka eggs
They are 0.3-0.8 mm in diameter (lice comb should have fine teeth spaced 0.2-0.3 mm apart)
Viable nits generally blench in with hair colour and are located 4-6 mm of the scalp
20
Q
What’s a pseudonit?
A
Not a nit
Could be dandruff
It’s easily detachable from the hair shaft (unlike a nit)
21
Q
If a nice is several inches away from the scalp, what does this mean?
A
The patient has probably had lice for a while and it’s probably an empty nit
22
Q
What are the signs and symptoms of body lice?
A
General itching around the waist, the wrists, etc.
It tends to be worse if the patient is wearing the clothes at night
23
Q
What are signs and symptoms of pubic lice?
A
Itching in the genital area
The nits will be found at the base of the hair follicle and much more difficult to find than head lice
Skin irritation due to hypersensitivity
Rust coloured specks in underwear
24
Q
How is head lice diagnosed?
A
Combing through the hair using a nit comb
If a nit is found in the hair, it’s only a modest predictor of a live infection
More than 5 nits within a cm of the scalp indicates a 32% change of live infection
The wet combing technique is recommended for diagnosis
25
Describe the wet combing technique
Wash hair and apply conditioner (leaving it in the hair)
Brush the hair with a normal brush to remove the tangles
It may help to separate the hair into sections with clips
Comb through hair with lice comb starting comb touching the skin of the scalp and comb to the edge of hair
Look carefully at the teeth of the comb in good light
Wipe the teeth with a piece of paper towel
Do this until the whole head has been combed through (this can take hours)
26
What should be considered for differential diagnosis of head lice?
```
Dandruff
Seborrheic dermatitis
Accumulation of hair cosmetics, paint flecks, or debris
Pseudo-nits
Psychogenic itch
```
27
What should be considered for differential diagnosis of pubic lice?
Seborrheic dermatitis
Folliculitis
Dermatophytosis (jock itch)
28
What should be considered for differential diagnosis of body lice?
```
Seborrheic dermatitis
Folliculitis
Eczema (atopic dermatitis)
Impetigo (bacterial infection of the skin)
Flea or insect bitse
Bed bugs
```
29
What is scabies?
Highly contagious infestation of the skin with the human mite Sarcoptes scabies var hominid
Children, mothers of young children, sexually active adults and elderly in nursing homes are at greatest risk
Epidemics occur in poor living conditions (poverty, poor hygiene, overcrowding) and institutions
30
Describe the scabies mite
Translucent, pearly white, flat
4 legs (compared to 6)
Generally there will be 10-15 mites on the body (there's one exception)
They are difficult to see with the naked eye
They are a mite that burrow under the skin and create a little trail
As they go along, they leave behind their feces and eggs
31
How many eggs do scabies mites lay?
2-3 eggs per day, with a 15-30 days lifespan
| The eggs hatch after 3-4 days and go through a molting process
32
How long can scabies mites live off a host?
Maximum 3-4 days
33
Describe scabies transmission
Primarily skin to skin contact but it can also be transmitted by fomites, such as couches, towels (extremely rare, unless the patient has a high parasite load)
34
What are the signs and symptoms of scabies?
Itch
Classically, there will be burrows between the webs of fingers
It may take 4-6 weeks for symptoms to develop for individuals without previous exposure (with previous exposure it takes 1-4 days)
It looks like almost anything (shingles, poison ivy, etc.), which is why it is important to refer these patients to the doctor to get a proper diagnosis
Scabies is very difficult to diagnosis
35
What is Norwegian or "crusted" scabies?
```
Atypical scabies presentation
Tends to occur in immunocompromised individuals
There are thousands of millions of mites
Lesions are not as red
It's more crusty and there's flakiness
```
36
What should be considered for differential diagnosis of scabies?
```
Seborrheic dermatitis
Impetigo
Body lice
Bed bugs/insect bites
Eczema (atopic dermatitis)
```
37
Are these parasitic skin infections self-treatable?
Head or body lice can be treated without consulting a doctor in most cases (self-treatable)
Patients with suspected pubic lice or scabies should be referred (not self-treatable)
Scabies requires a physicians diagnosis
Pubic lice means the person is at risk for STIs
38
What are red flags?
```
Presence of secondary bacterial infection in lice or scabies infested areas
Resistant/recurrent cases
Patients with suspected scabies
Patients with pubic lice
Lice infestation of eyebrows/lashes
```
39
What are non-pharmacological treatment and prevention options for lice?
Nit removal (decreases diagnostic confusion, decreases possibility of unnecessary re-treatment, decreases small risk of re-infestation)
Avoid sharing personal items
Items should be dry cleaned, washed in hot water (above 50ºC) or stored in plastic bags for 10-14 days
Soak combs and brushes in hot water (above 50ºC) for 5-10 minutes or wash with pediculicide
Carpets, rugs and furniture should be vacuumed
Close contact should be inspected for lice and all infested contacts should be treated at the same time to prevent re-infestation. Bedmates should be treated prophylactically
40
What are the goals of therapy for lice and scabies?
Exterminate scabies or lice
Relieve pruritus
Prevent secondary bacterial infection
Prevent the spread of the infestation
41
What does pediculicide activity mean?
Ability to kill lice
42
What does ovicidal activity mean?
Ability to kill viable eggs
43
What does residual activity mean?
Retention of pediculicide on the hair and scalp after washing
44
What are the chemical products available in Canada for lice and scabies?
```
Permethrin 1% (head lice) and 5% (scabies)
Pyrethrin with Piperonyl butoxide (PPB)
Lindane 1%
Isopropyl myristate 50%
Dimeticone 100 cSt 50%
```
45
What is the brand name, mechanism of action and indication of permethrin?
Brand names: Nix (cream rinse and cream) and Kwellada P (cream rinse and cream)
MOA: respiratory paralysis
Indciation: head lice and scabies (off-label: pubic lice)
46
What is the brand name, mechanism of action and indication of PPB?
Brand names: R&C and Pronto
MOA: respiratory paralysis
Indication: head and pubic lice (off label: scabies)
47
What is the brand name, mechanism of action and indication of lindane 1%?
Brand names: pms-Lindane and Hexit (lotion and shampoo)
MOA: seizures/paralysis
Indication: Head lice and scabies (off label: pubic lice)
48
What is the brand name, mechanism of action and indication of isopropyl myristate 50%?
Brand name: Resultz (liquid)
MOA: dehydration
Indication: head lice
49
What is the brand name, mechanism of action and indication of demeticone 100 cSt 50%?
Brand name: NYDA (spray)
MOA: suffocation (perhaps gut rupture)
Indication: head lice
50
Do the products available for the treatment for lice and scabies have pediculicide activity?
```
Permethrin: Yes
PPB: Yes (less effective than permethrin)
Lindane: Yes (less effective than PPB)
Isopropyl myristate: Yes (limited data)
Dimeticone: Yes (limited data)
```
51
Do the products available for the treatment for lice and scabies have ovicidal activity?
```
Permethrin: 70-80%
PPB: 70-80% (?)
Lindane: 50-70%
Isopropyl myristate: No
Dimeticone: Yes (limited data)
```
52
Do the products available for the treatment for lice and scabies have residual activity?
Only permethrin (maybe)
53
What are precautions for products used to treat lice and scabies
Permethrin: caution in children under 2
PPB: avoid contact with eyes and mucosal tissue (nasal, oral or genital)
Lindane: caution with children under under 10, elderly, and patients with seizure disorders
Isopropyl myristate: not recommended for children under 2 and avoid contact with eyes
Dimeticone: not recommended for children under 2 and void contact with eyes. Mixture is volatile; keep it away from sources of ignition, open flames, lit cigarettes
54
What are the contraindications for products used to treat lice and scabies?
Permethrin: allergies to ragweed and chrysanthemum which may lead to cross-sensitivity
PPB: allergies to ragweed, chrysanthemum or petroluem products which may lead to cross-sensitivity
Lindane: patient with extensively excoriated skin, the elderly and children may have enhanced percutaneous absorption and increased potential for toxicity
Isopropyl myristate: none known
Dimeticone: none known
55
What are the kinetics of the products used to treat lice and scabies?
Permethrin: 2% systemic absorption, rapidly inactivated, no active metabolites, renally excreted in 72 hours
PPB: minimal absorption, rapidly metabolized
Lindane: 10% systemic absorption and is slowly metabolized so accumulates with repeated exposures
Isopropyl myristate: not available
Dimeticone: not available
56
Can patients who are pregnant or breastfeeding use products for the treatment of lice and scabies?
```
Permethrin: considered compatible
PPB: considered compatible
Lindane: not recommended
Isopropyl myristate: no data available
Dimeticone: no data available
```
57
What are the side effects of permethrin?
Mild transient itching, redness and swelling
| Uncommon adverse effects include burning, stinging, rash, tingling and numbness
58
What are the side effects of PPB?
Contact dermatitis due to the petroleum distillates used for solvent purposes in the formulation
59
What are the side effects of lindane?
Slight local irritation.
Neurotoxic (dizziness, nausea, vomiting, hallucinations, abnormal movements, seizures)
Aplastic anemia
60
What are the side effects of isopropyl myristate?
Local irritation with mild erythema and scalp pruritus
61
What are the side effects of dimeticone?
Mild itching, ocular irritation
62
What is pediculicide resistance?
It have developed in countries with heavy pediculicide use (UK, Czech, France)
Prevalence is unknown
Resistance patterns appear highly variable from community to community and country to country
63
What is the possible mechanism of resistance?
```
Knockdown resistance (kdr) - sodium channel gene mutation
Enzyme up-regulation (glutithione S-transferase)
```
64
What choice of non prescription products to treat lice depends on what?
```
Local resistance patterns
Previous treatment
Product efficacy
Safety considerations/patient characteristics (red flags, contraindications, age, allergies, etc.)
Ease of administration
Cost
Patient preference
```
65
Why does lindane have a high risk of toxicity?
It has a 10% systemic absorption rate
It is highly lipid soluble
It's metabolized in the liver
It has a half life of 18-24 hours
66
How should permethrin be applied?
```
Towel dried hair
Short hair 30ml, long hair 60 ml
Shake well, saturate hair and scalp
10 minutes, rinse, remove nits
Reapply 7-10 days later
```
67
How should PPB be applied?
```
Dry hair
Short hair 25 ml, long hair 100 ml
Saturate hair, massage into scalp
10 minutes, add small amounts of cool water, massage until lather forms, rinse, remove nits
Reapply 7-10 days later
```
68
How should lindane be applied?
```
Dry hair
Short hair 15-30 ml, long hair 60 ml
Shake well, saturate hair and scalp
4 minutes, add small amounts of cool water, massage until lather forms, rinse an remove nits
Reapply 7-10 days later
```
69
How should isopropyl myristate be applied?
```
Dry hair
Short hair 30-60 ml, medium hair 60-90 ml, long hair 90-120 ml
Saturate hair, massage into scalp
10 minutes, rinse, remove nits
Reapply 7 days later
```
70
How should dimeticone be applied?
Dry hair
Short hair 10 ml, medium hair 18 ml, long hair 22ml, very long hair 22 ml
Screw pump on, spray hair to saturate and massage into scalp
30 minutes, DO NOT RINSE, remove nits, leave on hair to dry at least 8 hours, wash out with normal shampoo
Reapply 8-10 days later
71
What is important with application of nonprescription products for treating head lice?
When using permethrin, don't use conditioner because it makes the hair smooth.
All other treatments are on dry hair
Second treatment is very important. Day 9 is the best day (the nits will have hatched but the nymphs won't have melted to reproduce
72
What should be done when head lice treatment fails?
```
Consider: midiagnosis, improper application (incorrect technique, insufficient amount, second treatment not given or inappropriate interval), re-infestation, resistance
When properly applied treatment fails, switch to a product in a different pharmacological class
Other therapies including the use of prescription products in conjunction with non-prescription products may also be needed
```
73
What are alternative therapies to treat head lice when standard therapy fails?
Permethrin 5% left on hair overnight covered with plastic shower cap
Septra DS BID 10/7 and Nix 1% applied for 10 minutes on days 1 and 7-10
Crotamiaton applied to scalp for 24 hours or 2 night time applications
Ivermectin 200ug/kg as a single dose followed by a second dose in 7-10 days (do not use in children less than 15 kg)
Herbal treatment, such as tea tree oil, lavender oil, etc. (they lack adequate date to show efficacy of herbal agents and also side effects are possible)
Home remedies (hair day, mayonnaise, petroleum jelly, cetaphil DO NOT WORK)
"Bug busting (wet combing technique every 3 days for 3 weeks - low efficacy)
Head shaving is effective but unnecessary
74
How should pubic lice be treated?
Pediculicides that are used to treat head lice are effective for pubic lice also (lindane is not recommended due to potential toxicity)
Use of permethrin 1% cream rinse or pyrethrins with PPB applied to affect areas are first line options
Sexual contacts within the previous month should be treated
If pediculicide causes itching treat with oral antihistamine or topical corticosteroid
75
How should pubic lice be treated if eyelashes are infested?
Remove nits and lice using tweezers then apply white petroleum (Tears Naturale is ophthalmic grade) twice daily for 10 days
76
How should body lice be treated?
Pediculicides are unnecessary (exception is if lice are adherent to body hairs)
Hygienic measures treatment of choice are bathing, launder items in hot water/dry clean, seal items in plastic bags for 10-14 days, improve living conditions, isolated from close contacts for 24 hours
77
What are the monitoring parameters for the detection of live lice
Patient should monitor daily for 2 weeks
There should an absence of live lice after 24 hours of applying pediculicide
Treat again with pediculicide 7-10 days after initial application to eradicate any recently hatched immature nymphs. Presence of adult lice may indicate resistance and need for change of therapy
78
What are the monitoring parameters for the presence of nits?
The patient should monitor daily for 2 weeks
There should be an absence of nits
Actions: Vinegar, nit comb to physically remove dead nits
79
What are the monitoring parameters for pruritus?
Patient should monitor daily for 2 weeks
There should be relief of pruritus
Actions: oral antihistamines, topical corticosteroids
80
What are the monitoring parameters for inflammatory pustules?
Patient should monitor daily for 2 weeks
| There should be clearing of any lesions and return to normal appearance of the skin within 1 week of treatment
81
What are nonprescription products used to treat scabies?
Definitive diagnosis is to be made by a physician prior to treatment
Infested persons and their close physical contacts form the previous 2 months should be treated at the same time, whether or not symptoms are present (they don't need to see a physician if the infested person has a confirmed diagnosis)
82
What are non pharmacological treatment and prevention options for scabies?
Wash clothing and linens in hot water with soap and then through the hot cycle of the dryer
Store unwashed clothing in a plastic bag for 5-7 days
Vacuum rugs, furniture and un-washable items
Avoid body contact with others until treatment is complete
83
How is scabies treated?
Apply to clean, cool, dry skin
Massage cream into skin from neck to soles of fee (NB crevices, fingers, toes, nails, armpits, genitalia) and put on clean clothes
If hands are washed, reapply
Move after 8-14 hours by taking a shower/bath and dress in clean clothes
Reapply after 7 days if necessary
84
What are the dosing recommendations for Nix for scabies
Nix 5%
For adults and children over 12: 30 g tube
For children between 5-12: 15 g
Children between 2-5 years: 7.5 g
Children under 2: 4-7 g
Obese people may need more than 30 g
If scalp is involved, it may require more
85
What are second-line treatments for scabies?
Lindane, crotamition an sulfur have produced equivocal results suggesting there is no most effective second-line agent
Some date suggests that crotamion is less effective and resistance has been reported with its use
Precipitated sulfur 7% in petrolatum (applied daily after a bath and left on for 24 hours for 3 days. Watch for unpleasant odour and local irritation)
86
What are the monitoring parameters for burrows (scabies)?
Patient should monitor daily for 2 weeks and pharmacist at next visit
End point: clearing of burrows over the following 2 weeks and return to normal skin appearance
Actions: if new burrows are detected, then pretreatment with a scabicide is necessary. Ensure nonpharmacologic measures are utilized
87
What are monitoring parameters for papules (scabies)?
Patient should monitor daily for 2 weeks and pharmacist at next visit
End point: clearing papules and return to normal skin appearance
Actions: if new papule are detected, then pretreatment with a scabicide is necessary after 7-10 days. Ensure nonpharmacologic measures are utilized
88
What are monitoring parameters for pruritus (scabies)?
Patient should monitor daily for 2 weeks and pharmacist at next visit
End point: Itching should resolve within several (up to 4) weeks. Itching beyond 4 weeks requires reinvestigation of the cause
Action: if itching persists for several weeks, then antihistamines, corticosteroids or crotamiton may be tried as antipruritic agents
89
What are the monitoring parameters for pustules and impetigo (scabies)?
Patient should monitor daily for 2 weeks and pharmacist at next visit
End point: this secondary infection should improve with 3 days of topical antibacterial (bacitracin/polymyxin B) treatment
Action: if not improvement or getting worse within 3 days of treatment, refer patient to a physician
90
For how long can transmission occur?
Transmission can occur as long as the infested person remains untreated and until 24 hours after treatment
