SCABIES: Types, Causes, Symptoms, Diagnosis and Treatment

The skin condition known as Scabies is caused by the Sarcoptes scabiei var hominis mite. The little red rashes and agonizing itching is caused by these insects which are burrowing into your skin. Scabies spreads quickly, especially among close-knit communities. If one family member has Scabies, a practitioner should check and treat other family members and close contacts at the same time.

Although Scabies is a problem everywhere, it tends to happen more commonly in hot and crowded areas. Infestations are present on the surface of the skin but do not reach the bloodstream.

Scabies is also known as sarcoptic mange. Animals can also get Scabies, but their mites are slightly different. Typically, pet-infesting mites cannot adapt to living on humans. 

Read this blog further to get a quick overview of this important topic for anatomy and ace your NEET PG exam preparation.

 Sarcoptes scabiei 

Mite has four pairs of legs. It has both Male mites and Female mites. After copulation male mites die.Hence, the female mites are responsible for infestations. Normally, in Scabies patients, 10-12 mites are found. Female mite infests the skin and then it starts forming a tract.

The formation of the tract starts from the stratum corneum and goes deeper. At the end of the tract, it lays down its eggs. The tract laid down by the female mite in our skin is called the burrow. This burrow starts from the stratum corneum and goes up to the stratum Malpighi

The lifecycle of the mite is like

• Egg
• Larva
• Nymph
• Adult

Types of Scabies

These are of different types: 

• Crusted Scabies
• Atypical Scabies: It includes
  • Infantile Scabies
  • Nodular Scabies
  • Animal Scabies
  • Genital Scabies

1. Crusted Scabies

It is also known as  Norwegian Scabies (first found in Norway). It is the Most severe form. This occurs in patients who cannot scratch as scratching is a protective phenomenon.It mainly occurs in patients with:

• Neurological disorders
• Down syndrome
• It also occurs in
• Immuno-compromised patients 
• HIV patients
• Older patients

As these patients will not scratch, the burrows will be accumulated. Hence, heaped-up crusts will be formed which are known to be crusted Scabies. In these conditions, millions of mites are present (Severe Scabies). It is responsible for institutional outbreaks. These patients admitted to hospitals. They are treated with both Topical and Oral drugs.

2. Infantile Scabies
   • In this type of Scabies Infants are affected. Regions involved are Face, Palms and Soles.     Vesicles are also formed as the infant is unable to scratch.These regions' involvement is not seen in adults. For treatment local application of cream is given for the face.

3. Nodular Scabies
   • Nodules are formed in the genital and axillary regions.This results in delayed-type hypersensitivity reaction.

4. Animal Scabies
   • In this type of Scabies Burrows are absent.

5. Genital Scabies

 In this patient is presented with genital manifestations.We should diagnose the patient for STI (both children and adults).

Clinical Presentations

• The incubation period is 3-4 weeks. If the patient is getting a secondary  infection then the Incubation period is 2 weeks

• Symptoms- Nocturnal itching (increased itching at night)  and Positive family history 

• Site
• Interweb space (fingers)
• Wrist
• Popliteal fossa
• Axilla
• Chest
• Umbilicus
• Genitals
• Mites will form an imaginary circle in the body called as Circle of Hebra 

 Presentation            

• Scabies- papules

These are Itchy and Excoriated papules. Vesicles are rarely present and are not seen because patients excoriate them. These papules are mainly Present on interweb fingers with nocturnal itching and Positive family history

 Other classical lesions are

• Burrow

Burrow, is a special lesion in Scabies. It is a tract created by the female mite. Clinically it appears as a linear wavy lesion. These are seen in Interweb spaces and Wrist. It is not seen commonly because we scratch the burrow. Scratching is a protection phenomenon through which you are destroying the path where the female lays the eggs. Stratum corneum is affected but it can go up to stratum Malpighi.

Diagnosis

Mostly, diagnosis is based on the clinical examination. Clinical diagnosis can be done based on

• Nocturnal itching
• Positive family history
• Typical sites being involved
• Presence of the burrow

Slide preparation

A wet mount can be made if we are not clear about the symptoms. From the burrow, scrap the skin and mount it under normal saline or cuvettes. On the wet mount, we will find

• Mites
• Sometimes eggs

Mite's eggs and fecal material are known as scybala.

Treatment

General measures

• Treat all family members to avoid transmission irrespective of their symptoms.
• Treat linen and clothing 
• Treatment is available against the mite, not against the eggs.
• So, the patient should take the treatment after 1 week (because the eggs will eventually convert to mites)
• Hence, repeat the treatment for 1 week 

Topical drugs for Scabies

• 5% Permethrin
• 1% GBHC (Gamma benzene hexa chloride)
• 25% Benzyl benzoate
• Malathion
• Crotamiton
• Precipitated sulfur
• Permethrin is the only drug of choice for all age group patients.
• Except, if the child is less than 2 months then the recommended drug of choice is Precipitated sulfur.

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