36. <<Primary Lesions>>
• Macules & Patches
- Discoloration of the skin
- macules less than 1 cm in diameter
- patches larger than 1 cm in diameter
37. ***The change is colour may result from pigment
loss or excess, erythema or haemorrhage.
38. Papules & Plaques
• A circumscribed, solid elevation of the skin
• Papules less than 1 cm in diameter often
pink and red
• Plaques larger than 1 cm in diameter
39.
40. Pustules
• Circumscribed elevations of the superficial
layers of the epidemis
• Bacterial infection
• The infiltrate will contain neutrophils,
bacteria, debris and perhaps a few free
keratinocytes
42. Wheals
• More or less well-defined
elevations of the skin due to edema
• Round, oval or plaque-like
• Disappears within minutes or hours
**angioedema
*Localised mast cell
degranulation within
the skin
43. Vesicles & Bullae
• A well-demarcated elevation of the
superficial layers of the skin
• Vesicles less than 1 cm in diameter
• Bullae lager than 1 cm in diameter
58. Diagnostic Test
• Trichogram
Identification of fur mites, adherent egg
cases, fractured ends to the hair shaft
** Trichograms are not a reliable method of diagnosing, or ruling
out, ectoparasite infections
59. Method
• Remove a small tuft of hair with fingers
or forceps
• Laid onto trasparent adhesive tape
• Laid onto a glass slide
• Microscopic examination
60. Adhesive tape stripping
• Allows direct sampling of the coat or skin
surface&hair
• Observes squamous morphology, ectoparasites and
micro-organisms
61. Method
• A commercial, clear, adhesive tape is
gently pressed onto the clipped skin
surface
removed
stained with Diff Quick
Laid across
A glass slide
Laid across a glass slide
62. Skin scraping
• This procedure samples the surface, the
epidermis and the upper dermis
• Indication of Demodex spp., Sarcoptes
scabiei and Cheyletiella spp.
• Indication of dermatophytosis spores
63. Method
• Parasites Clip hair
Liquid paraffin is applied to the skin surface & slide
Dragged across the tensed skin repeatedly by the blade
Transfer accummulated sample to the slide
64. Method
• Dermatophyte
Clip hair
10%KOH applied to the skin surface & slide
Dragged across the tensed skin repeatedly by the blade
Transfer accummulated sample to the slide
Heat fixing
Stained with Lactophenol cotton blue or India ink
65. Wood’s light
• Indication of Microsporum canis,
Microsporum distortum, Microsporum audoinii,
Trichophyton scnoenleinii
• False positive : Pseudomonas spp.,
Corynebacterium spp., keratin, soap,
petroleum and some drugs.
67. Fungal culture
• The scale and hair are inoculated onto a
culture plate containing a medium
68. Otic sampling
• Indication of Malassezia
pachydermatis, bacteria and mites
• Method
the sample is collected with a cotton swab
dry
fixing
staining
69. Impression cytology
• Used to sample cells from the surface of
erosions and ulcers or from the orifices of
discharging fistulae
• Medthod
Pressing a cleaned glass slide against the lesion
dry
Staining with Diff Quick
70. Aspiration cytology
• Used to sample cells from within lymph
nodes, nodules and neplasms
• Method Needle aspiration
smear
dry
Staining with Diff Quick or special stain
72. Intradermal skin testing
• Demonstrate the presence of allergen-
specific IgG on the mast cells at the site of
the intradermal injection
• Method
73. Punch biopsy
• Obtain samples for histopathological
examination
• Method Select site
Local anesthesia
Push biopsy punch through the skin
Remove sample & placed into 10% formaline
