Demodex

Demodex

Article originally written by Indrakala Khatri , B.V.Sc and A.H, IAAS

1. Introduction

  • Demodex is a genus of very minute follicular mites  (family: Demodicidae) that inhabit the skin and are  usually found in the sebaceous glands and hair  follicles of mammals.
  • They are considered to be host-species specific and  some can be infested with two or more distinct  species such as;
  • D. canis ( in dog)
  • D. injai (in dog)
  • D. Brevis ( in human)
  • D. folliculorum ( in human)
  • D. bovis (in cattle)
  • D. caprae (in goat)

2. Morphology

  • Long and thin, like a cigar and  usually about 0.25 mm long.
  • Body have head, thorax with four  pairs of stumpy legs and elongated  abdomen.
  • Mouth with paired of palps and  chelicerae and an unpaired  hypostome.
  • In male penis protrude dorsally  while in female vulva protrude  ventrally
  • Eggs – spindle shaped

3. Lifecycle

Complete entire lifecycle within hair follicle and sebaceous glands of  single host at about 20-35 days (D. canis).

4. Pathogenesis

  • Usually non pathogenic; remain as commensals under normal health  condition.
  • but under immunosuppressive condition due to stress/illness mite (D. canis) proliferate and demodicosis (demodectic mange) is  diagnosed.
  • Infection may be localized, generalized or pododermatitis

Demodicosis can manifest as lesions of two forms :

A. Squamous form

Distended hair follicles with mites and cellular debris.

Follicular epithelium is atrophic.

Hyperkeratosis.

Hyperpigmentation with copper- red color skin.

Alopecia

Thickened skin and mousy odour.

B. Pustular form

Suppurative bacterial invasion of dermis.

Extensive dermal infiltration of polymorphonuclear leucocyteses and  lymphocytes.

Abcess formation with marked inflammation.

Inextensive form of canine demodicosis, death results from toxaemia  or emaciation.

5. Symptoms

  • Slight to moderate itching.
  • Patchy hair loss and leaves bald.
  • Red, weepy infected areas.
  • Cornified materials exfoliate from  surface.
  • Thickened skin.
  • Emaciation

6. Diagnosis

  • By finding mites in
  • Contents of abscess
  • Skin scraping: initially skin is pinched or squeezed gently then, scraped with  dull tool like back of scapel blade; deep enough to assure sampling of hair  follicle until tiny bleeding by capillary oozing. Finding many mites in  scrapped material under microscope diagnosed    an infection.
  • Pets with cancer, hypothyroid diseases, allergies, heart worm infection may  develop mange infection so following test may be done.
  • Fecal exams.
  • Blood test for heart worm, liver and kidney function.

X-ray for lymphocarcinoma

7. Differential diagnosis

Sarcoptic mange

8. Treatment

  • Amitraz ( mitaban dip) : 1 bottle of amitraz with 2 gallons of warm  water( 250ppm).
  • Ivermectin : 0.4 – 0.6mg/kg, PO, once daily.
  • Bacitracin topical
  • Milbemycin : 0.5-2mg/kg orally once daily for three month

Reference

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