Skin and hair sampling - lab session

Question 1

How do you perform a tape impression?

Answer 1

Cut a length of Sellotape
- longer than a microscope slide

Apply tape onto skin area
- separate hair to get good contact
- try not to touch sticky side (edges fine)

Rub tape with thumbnail to ensure good contact

Fold the tape over the slide with the sticky side facing out ready for staining

Diff-quick the slide

Question 1

What can be diagnosed from a tape impression?

Answer 1

X10 X40 objective lens
- superficial ectoparasites
- eg fleas, flea dirt, lice, cheyletiella, otodectes, harvest mite

X100 oil immersion objective lens
- Bacteria
- Fungi-spores
- Yeasts (e.g. Malassezia)
- Cells (e.g. neutrophils(

Question 2

How do you perform direct impression?

Answer 2

Perform on exudative lesions
- If non–exudative can be ‘picked’ with a needle to express fluid

Gently press the slide onto the lesion

Air-dry
Stain with diff-quick

Question 3

What can you diagnose with a direct impression?

Answer 3

X100 objective lens oil immersion
- Bacteria, Fungi and Yeast
- Inflammatory cells - neutrophils, eosinophils, lymphocytes, macrophages
- Smears from biopsies - Mast Cell tumours

Question 4

How do you perform hair brushing sample?

Answer 4

Brush hair over black consulting table or white/brown paper

Place hairs in petri dish and cover in liquid paraffin
OR
Place scale/parasites on slide with liquid paraffin

Examine under microscope

For fleas: rub suspected flea excrement on damp paper towel - if red/brown then present

Question 5

How do you perform skin scrapes?

Answer 5

Place 1 drop of liquid paraffin in the centre of the microscope slide ready for the scraped material

Apply one drop of paraffin to the skin surface and spread with your finger
- pinch and roll the skin prior to scraping – this will force demodex from the hair follicles

Scrape the blade at a 45 degree angle along the skin following the direction of the hair
- continue until there is ‘capillary ooze’

Tap or scrape the blade in the drop of paraffin on the slide to dispense your sample

Place a coverslip over the area and gently press onto the sample

Question 6

How do you swab a sample?

Answer 6

Rub swab over skin / gently around external ear
- if area is dry then dampen area with saline/paraffin

Roll swab along microsope slide
- can also suspend large blobs of earwax in paraffin

Add cover slip

Question 7

What can you diagnose with a swab sample?

Answer 7

X4/ X10 objective lens
- Otodectes cynosis

X100 oil immersion
- Fungi
- Ringworm
- Yeast- Malassezia
- Bacteria
- Inflammatory cells - neutrophils, eosinophils, macrophages, lymphocytes