6. Scabies

  • Caused by


  • Commonest, pruritic, parasitic disease caused by an itch mite, Sarcoptes scabei var hominis, an acarus (mite)
  • Transmitted by close personal contact and sexual contact
  • Incubation period of 2 to 4 weeks [Duration between entry of organism and the development of the first symptom]


  • 300M cases worldwide
  • All ages, sexes, ethnic and socioeconomic growth
  • More in winter, throughout the year

Modes of Transmission

  • Closed personal contact
  • Sexual
  • Fomites [[Pasted image 20210623102057.png]]


Life Cycle

[[Pasted image 20210623102133.png]]


  • Delayed hypersensitivity to mite or its products are responsible for the lesions and pruritus

Clinical features

  • Itching - worse at night with skin rash
  • Family members affected


  • Characteristic distribution along the circle of Herba

  • Papules, vesicles

  • Burrow-grey-brown line 5mm, seen on webs and genitalia with mite as black dot at end

  • May be a dot, dotted line, curve or curved line [[Pasted image 20210623102714.png]]

  • To confirm diagnosis circle of herba


  • Secondary infection
  • Eczematization
  • Rarely glomerulonephritis when there’s a secondary infection of S
  • Phimosis, Paraphimosis
  • Erythroderma
  • Drug reactions on wrong application may lead to eczematization

Clinical types

Infantile scabies

  • Involvement of palms and soles and face
  • Adult versions do not involve of palms and soles as skin is thick and cannot burrow and face is richly supplied by sebum thus there’s no face involvement
  • Differnetial diagnosis w/ Atopic dermatitis -

Norwegian scabies

  • No itching
  • millions of mites
  • Hyperkeratotic crusted lesions on palms and soles
  • Seen in Mongoloids, Mentally retarded, lepromatous leprosy, tabes dorsalis, immunosuppressive patients [Immunocompromised and De-sensitive group]

Nodular scabies

  • Nodules in

Scabies incognito

  • Secondary to application of topical/oral steroids
  • Symptoms are only treated - subside with steroids
  • Unusual presentation
  • Atypical sites

Animal scabies

  • Sarcoptes scabie var canis
  • Infests dogs, cats, horses etc
  • Differ biologically but morphologically
  • No burrows
  • Human to human transmission does not occur


  • Itching more at night
  • Family history
  • Typical sites of distribution
  • Demonstration of the mite


  • Treat secondary complications first
  • Treat alll the household members
  • Treat all inmates and caretakers in institution
  • Treat fomites by puttng in hot water, insecticides, for 2-4 days
  • Scabicides to be applied behind ears

[[Pasted image 20210623104849.png]] [[Pasted image 20210623104925.png]]

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