Bites and Infestations Flashcards
General Findings
and
History
General Findings:
-Pruritic, erythematous papules
+/- excoriations
Vesicular and bullous reactions
-Role of immune system
Systemic reactions
Severity / persistence of symptoms
History:
- Environment (work, recreation, home)
- Contacts (social, sexual)
- Pets
- Lesion evolution
- Symptoms: Pruritus
Specific Anthropods
¨ Scabies
¨ Pediculosis (lice)
¨ Fleas **leave an obvious bite rxn
¨ Chiggers ***leave an obvious bite rxn
¨ Bedbugs
¨ Ticks
Lyme Disease
Rocky Mountain Spotted Fever
Scabies Overview
- Sarcoptes scabiei var. hominus
- Usually 10-15 mites on host
- Female burrows 2-3 mm daily in the epidermis (usually at night)
- 30-day lifespan
- Lay 60-90 eggs
-Eggs hatch in ~3 days
*important for treatment choices
- Mites mature in ~14 days
- Mite can survive 2-3 days off host
- Transmission
Close contact, skin to skin, bedding, linens, clothing
-First infestation can take 2-6 weeks before immune system is sensitized
-Symptoms can persist 3-6 weeks after primary infestation
-Hypersensitivity to mites/feces
Scabies Life Cycle
Scabies: Physical Exam Findings
Primary lesions
- Burrows: raised, pink/white lesions with mild surrounding erythema
- Straight, curved, or S-shaped line; 2-5 mm
- Small erythematous papules, vesicles
- Papules rarely contain mites, common on genitals
Secondary lesions (manipulation by patient)
- Excoriations
Physical exam may differ in special types
Variants of Scabies
-Nodular / bullous: Infants
-“Scabies incognito”
*_Topical steroids mask r_esponse (atypical distribution)
-Norwegian (crusted scabies)
- Compromised immune system
- Elderly
- HIV / AIDS
- Solid organ transplant recipients
- Decreased sensory function (leprosy, paraplegia)
Nodular Scabies
- Pink-tan-red-brown nodules 2-20 mm in size
- Mite usually not present in the nodule
- Nodules can persist after treatment
*Much larger than burrows
Scabies Norwegian
- Occurs in the immunocompromised, debilitated
- Itching may be minimal (50% have no itch)
-Very contagious –infested with > 1 million mites
-Primary lesions
- Hyperkeratotic, crusted, plaques
- Cover large areas, nail dystrophy, scalp lesions
- May resemble psoriasis
Scabies Diagnosis
- Clinical suspicion; use a hand lens to examine skin
- Skin scraping
- Higher yield when burrow scraped toward the terminal end
Scabies Treatment
Permethrin 5% cream (Elimite)
- One 30 g application/adult, repeat in 1 week
Lindane 1% lotion (neurotoxicity in children)
- Repeat in 1 week
- rarely used
Ivermectin (PO) 200 mcg/kg
- Repeat in 1 or 2 weeks
Sulfur (5% in petrolatum)
- apply nightly X 3 nights
Anti-pruritics
Scabies: Important treatment notes
- Apply the prescribed amount from neck to toes
- Treat close contacts, even if asymptomatic
- Repeat applications may be required
- Wash clothing and bedding in hot water
- For nursing/pregnant mothers or very young infants, use Permethrin or sulfur
- Itching and lesions may persist after treatment
Pediculosis Overview
“lice” /“louse”
- Wingless, flat-bodied organisms
- Blood-sucking
Nits
- egg casings
- Incubation 9-12 days
Adults
- by 19-27 days
- Can survive off host up to 2-3 days
Types of Pediculosis
- Pediculus humanus capitis*
- Head louse
- Pediculus humanus var corporis*
- Body louse
- Phthirius pubis*
- Pubic louse / “Crabs”
Pediculosis Capitis
Epidemiology
- Affects all socioeconomic levels
- Children most commonly affected (F>M)
Transmission
- Spread via head-head contact and fomites
- Hats, caps, brushes, combs
Symptoms
- Bites are painless
- Pruritus arises from the host’s immune response and depend on the individual’s sensitivity
Clinical Feature
- Scalp – occipital & post-auricular regions
- Pruritic papules, acute hive-like reaction
- Erythema
- Scaling
- Linear excoriations
Pediculosis Capitis
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