Scabies

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CLINICAL DESCRIPTION

Intensely pruritic skin condition caused by the mite Sarcoptes scabiei. Humans are the only hosts of this mite and therefore infection is from human to human. Transmission is common among overcrowded populations e.g., schools and among those that may have close body contact like household members, children during playing and sexually active adults.

Symptoms are due to delayed type hypersensitivity reaction to the mites, their eggs and their excreta. The hypersensitivity reaction may take several weeks to develop hence patients may become symptomatic only later on after their primary infection.  This period may be shorter during reinfection. Untreated contacts will keep the transmission going in the population and hence all contacts of scabies patients must be treated alongside the patients.

Sites of predilection of scabies

  • Interdigital web spaces of hands
  • Flexor surfaces of wrists
  • Extensor surfaces of elbows
  • Periumbilical skin
  • Genitalia
  • Buttocks

CLINICAL FEATURES

SIGNS AND SYMPTOMS
  • Intense Pruritus in the patient and their contacts or family members.
  • Vesicles, papules, excoriations, burrows and on affected areas
  • Secondary infection may be found due to bacterial colonization of excoriated areas.
  • In babies, lesions may also be found on the palmar and plantar skin.
INVESTIGATIONS
  • KOH exam can detect eggs and mites but not necessary. It is mostly difficult to find the eggs and mite except in crusted scabies where there are many mites

TREATMENT

  • Apply Benzyl Benzoate Emulsion 25% in the evening to the whole body from the neck down
  • Ensure all parts of the skin are covered
  • Allow the medication to remain on the skin overnight
  • Apply on day 1, 2 and 3.
  • Next morning wash off the application with Soap and water
  • Repeat the above treatment on day 8, 9 and 10

Alternative for Benzyl benzoate application

  • Permethrin 5% cream apply at night, wash in morning; repeat after 1week.
  • Apply Lindane 1% lotion, single dose applied as above

Note:

  • Avoid Lindane in children less than 2 years old
  • In children under 1 year, also treat the face (except the area surrounding the eyes)
  • For children under 5 years, use 12.5% benzyl benzoate application
  • Prepare this by diluting 25% benzyl benzoate emulsion in equal volumes of water e.g., mix 1ml of BBE and 1 mL of water.

In cases of secondary bacterial infection, treat that too:

For itch:

  • Chlorpheniramine 4-8 mg at night for 2-3 weeks
  • Note that even after successful treatment, itching may persist for up to 2-3 weeks.
  • There is no need to repeat BBE if both index and contact treatment was adequate but rather just continue treating the itch.