Infestations Flashcards
What is scabies?
A pruritic condition caused by infestations with the host specific mite - Sarcoptes Scabei var hominis
Sarcoptes Scabei Var canis (and other animal infestations) are NOT a source of infestation for humans. They can produce bite reactions.
What is the name of the mite that causes scabies?
Sarcoptes Scabei var Hominis - in humans.
What are the key clinical features of scabies?
Intense pruritis, symmetrical cutaneous lesions, erythematous papules, excoriations, vesicles, indurated nodules, eczematous dermatitis, acral vesicopustules, burrows.
Burrows are wavy, thread-like, gray-white and 1-10mm in length.
How is scabies transmitted?
Directly - via close personal contact, indirectly - via fomites.
What does the scabies mite look like?
An eight-legged mite.
Describe the scabies life cycle.
30 days, happens within the epidermis. Female copulation occurs ONCE per adult female lifetime. Each female mite lays 2-3 eggs per day. An egg takes ten days to mature.
Who does scabies affect?
Children > Adults, sexually active individuals.
Who does crusted scabies affect?
Patients with a compromised immune system, including those with HIV, HTLV-1, solid organ transplant, decreased sensory function, and inability to scratch (infants).
How many mites are on an infected person?
Varies greatly, normally fewer than 100 (no more than 10-15); crusted scabies = thousands.
How long can a scabies mite live off a human host?
~ 3 days, unless crusted scabies (7 days - as feed off sloughed skin).
How long after infection does a person become symptomatic?
Takes 2-6 weeks for the host to become sensitized to the mite or its byproducts; within 24-48 hours for subsequent infections.
What are some complications of scabies?
Secondary skin infection (Staph Aureus, Strep Pyogenes), post-strep glomerulonephritis, peripheral eosinophilia, sleep disturbance, psychological distress.
What investigations would you do for scabies?
Often a clinical diagnosis, light microscopy examination of mineral oil preparations of skin scrapings, biopsy will only be diagnostic if mites are biopsied.
What are the techniques of performing light microscopy?
Skin scrapings - mineral oil preparation, transparent adhesive tape applied to infestation areas of skin.
What are the dermoscopy features of scabies?
Dark, triangular shape representing the head of the mite within a burrow (‘delta wing’ sign) or jet with contrail.
What are the histological features of scabies?
A patchy to diffuse infiltrate in the reticular dermis, prominent eosinophils, lymphocytes, histiocytes, pink ‘pigtail like structures’ attached to the stratum corneum.
What is a differential diagnosis for scabies?
Insect bite reaction, papular eczema, ID reactions, atopic dermatitis, allergic contact dermatitis, dermatitis herpetiformis, bullous pemphigoid, acropustolosis of infancy, eosinophilic folliculitis.
List 6 topical treatments for scabies and one oral treatment.
- Permethrin 5% cream
- Sulfur ointment (5-10%)
- Benzyl benzoate lotion or emulsion (10-25%)
- Spinosad Suspension (0.9%)
- Crotamiton lotion
- Lindane lotion
- Oral: Ivermectin 200 mcg/kg.
What treatments are safe in pregnancy for scabies treatment?
Permethrin, Spinosad Suspension (0.9%), Sulfur ointment.
How does Permethrin work?
Inhibits sodium transport in the arthropod neurons, causing paralysis.
Apply to the neck down with special consideration to the fingers, web spaces, feet, umbilicus. Leave on overnight.
How does Ivermectin work?
Blocks nerve synapses - causes mite paralysis.
Dose on day 0 and on day 7.
Is Ivermectin safe in pregnancy or breastfeeding?
No.
What are the management options for scabies?
- First line: permethrin 5% cream (category B in pregnancy) and oral ivermectin 200 mcg/kg (avoid in pregnancy)
- Ivermectin for large outbreaks, nodular scabies, crusted scabies.
- Other treatments: benzyl benzoate, crotamiton, lindane, malathion, sulfur in petrolatum.
What is the method for applying Permethrin cream?
Massage thoroughly into skin from the neck down, including areas under fingernails and toenails. Treat every inch of skin.
Special attention to interdigital spaces, intergluteal cleft, umbilicus, and subungual areas.
