2. Introduction:
Skin scraping is a common
diagnostic technique used to
identify external parasites
and skin diseases in
animals.
It involves scraping the skin
with a scalpel blade and
examining the collected
material under a
microscope.
Skin scraping can be
superficial or deep,
depending on the type and
location of the parasite.
In this presentation, I will
focus on skin scraping in
dogs and cats, and discuss
the different techniques,
uses, instruments, and
interpretation of the
procedure.
3. History of
Skin Scraping:
Skin scraping is one of the
oldest and most widely used
diagnostic techniques in
veterinary medicine
first performed by Johann
Christian Gustav Lucae in
1847, who scraped human
skin lesions to demonstrate
Sarcoptes scabiei mites
It was later adopted by
veterinarians to diagnose
various parasitic skin
diseases in animals, such as
mange, ringworm and
cheyletiellosis
It has remained a valuable
tool for decades, despite the
development of newer and
more advanced methods,
such as molecular
diagnostics,
immunohistochemistry and
PCR
It is still considered the gold
standard for diagnosing
demodicosis in dogs and
cats
4. Diagnosis: Can help
identify the cause of
skin lesions, itching,
hair loss, or infection
in dogs and cats. Can
confirm or rule out
parasitic infestation or
fungal infection as the
primary or secondary
cause of dermatitis.
- Prognosis: Can help
assess the severity
and progression of
parasitic infestation or
fungal infection in
dogs and cats. It can
also indicate the level
of reproduction,
inflammation, or tissue
damage caused by
the parasites or fungi.
- Treatment: Can help
monitor the response
to treatment of
parasitic infestation or
fungal infection in
dogs and cats. It can
also show the
reduction or
elimination of
parasites or fungi from
the skin after therapy.
Uses for Skin Scrape:
5. Indications
for Skin
Scraping:
Skin scraping is indicated when there is suspicion of parasitic infestation or skin infection
in dogs or cats. Some of the common parasites that can be detected by skin scraping
are:
Demodex mites: These are cigar-shaped mites that live in the hair follicles and
sebaceous glands. They can cause demodicosis, a condition characterized by hair loss,
scaling, redness, and sometimes secondary bacterial infection. Demodex mites are
more common in dogs than cats, and can be found by deep skin scraping.
Sarcoptes mites: These are round mites that burrow into the epidermis and cause
intense itching, crusting, and alopecia. They can cause sarcoptic mange or scabies, a
highly contagious disease that can affect humans as well. Sarcoptes mites are more
common in dogs than cats, and can be found by superficial or deep skin scraping.
6. Indications:
(continued)
- Cheyletiella mites: These
are large mites that live on
the surface of the skin and
hair coat. They can cause
cheyletiellosis or walking
dandruff, a condition marked
by scaling, flaking, and mild
pruritus. Cheyletiellosis is
more common in cats than
dogs, and can be found by
superficial skin scraping or
tape impression.
- Notoedres mites: These
are similar to Sarcoptes
mites but smaller and more
oval-shaped. They can
cause notoedric mange or
feline scabies, a condition
that affects mainly the ears,
face, and neck of cats.
Notoedres mites can be
found by superficial skin
scraping.
7. Instruments
needed:
The basic instruments
needed for skin scraping
are:
A #10 scalpel blade: used to
scrape the skin gently and
collect the material; can be
dulled by scraping it on a
hard surface for superficial
scrapes or kept sharp for
deep scrapes
A glass microscope slide:
used to hold the collected
material and mix it with
mineral oil for examination
Mineral oil: used to lubricate
the scalpel blade and the
slide; also helps preserve
the parasites and prevent
them from drying out
A microscope: used to
examine the slide under low
to high magnification;
preferably with a light source
and adjustable objectives
A coverslip: used to cover
the slide and prevent
evaporation of the mineral
oil; also helps flatten the
material for better
visualization
8. Technique for
Superficial Skin
Scraping:
Used to detect parasites
that live on the surface
of the skin or epidermis,
such as Sarcoptes,
Cheyletiella, or
Notoedres mites.
The steps for superficial
skin scraping are:
Select an affected area
of skin that is not
infected or traumatized,
if possible. Avoid areas
with thick crusts or
scabs.
Place a drop of mineral
oil on a microscope slide
and on the scalpel
blade.
Scrape the skin in one
direction with light and
gentle pressure across a
broad lesional surface.
The goal is to collect
scales and debris
without causing
bleeding.
Transfer the scraped
material from the blade
to the slide with mineral
oil. Repeat 3 to 5 times
to cover the slide.
Apply a coverslip to the
slide and examine
9. Technique for Deep Skin Scraping:
Apply a coverslip to the slide and examine
Transfer the scraped material from the blade to the slide with mineral oil. Repeat 3 to 5
times to cover the slide.
Scrape the skin in one direction with firm and constant pressure until capillary bleeding
occurs. The bleeding indicates that the follicles have been reached.
Pinch or fold the skin with one hand and hold the blade firmly with the other hand.
Place a few drops of mineral oil on a microscope slide and on the scalpel blade.
Select an affected area of skin that is not infected or traumatized, if possible. Avoid areas
with thick crusts or scabs.
Deep skin scraping is used to detect parasites that live in the hair follicles or sebaceous
glands, such as Demodex mites. The steps for deep skin scraping are:
10. Alternative Techniques for
Skin Scraping:
In some cases, alternative
techniques may be used instead of or
in addition to skin scraping to detect
parasites. These include:
Tape impression: This involves
applying a piece of clear adhesive
tape to the skin and peeling it off
gently. The tape is then placed on a
microscope slide with mineral oil and
examined under 4X to 10X
magnification. Useful for detecting
Cheyletiella mites and fungal spores.
Hair pluck: This involves grasping a
tuft of hair with a hemostat and
pulling it out firmly. The hair is then
placed on a microscope slide with
mineral oil and examined under 10X
to 40X magnification. Useful for
detecting Demodex mites and fungal
elements.
Skin biopsy: This involves taking a
small piece of skin with a punch or a
scalpel and submitting it for
histopathology. Skin biopsy is useful
for confirming the diagnosis of
demodicosis or other skin diseases
that may mimic parasitic infestation.
11. How to Read a Skin Scraping
on a Microscope:
The following tips can help
read a skin scraping on a
microscope:
Adjust the light source and
focus: use the coarse and
fine adjustment knobs to
obtain a clear image of the
slide; adjust the light
intensity and condenser to
optimize the contrast and
brightness
Identify the parasites: use
a reference guide or atlas
to compare the
morphology, size and
features of the parasites;
note the shape, color,
segmentation,
appendages, mouthparts
and reproductive organs of
the mites;
Quantify the parasites:
count the number of
parasites per field of view
or per slide; note if they are
alive or dead, intact or
fragmented; report results
as negative, positive, low,
moderate or high
Interpret the results:
correlate the findings with
the clinical signs, history
and physical examination
of the animal; consider
other diagnostic tests, such
as culture, cytology or
biopsy, to confirm or rule
out differential diagnoses;
consult Vet if needed
12. Advantages:
Skin scraping has several advantages as a diagnostic technique,
such as:
Simplicity: it can be performed easily and quickly by any veterinary
staff member with minimal training and equipment
Cost-effectiveness: it is inexpensive and does not require expensive
reagents or consumables
Rapidity: it can provide immediate results that can guide treatment
decisions and client education
Sensitivity: it can detect low numbers of parasites that may be
missed by other methods, such as acetate tape impression or flea
combing
13. Disadvantages:
False negatives: May fail
to detect parasites that are
present in low numbers,
deep in the skin, or in
inaccessible areas. Can
lead to missed Dx or
delayed Tx
False positives: Can detect
parasites that are part of
the normal skin flora, such
as Demodex mites, in
asymptomatic animals.
This can lead to
unnecessary Tx or
overdiagnosis
Technique-dependent:
Skin scraping requires
proper technique,
pressure, direction, and
site selection to obtain
adequate samples for
examination. Poor
technique may result in
insufficient material,
bleeding, pain, or infection.
Interpretation-dependent:
Requires proper
magnification,
identification, and
quantification of parasites
on the slide. Poor
interpretation can result in
misidentification,
underestimation, or
overestimation of parasitic
infestation
14. Tips & Tricks:
To improve the accuracy and reliability of skin
scraping, some tips and tricks are:
Choose an appropriate site for scraping: select an area
that is representative of the disease process and has
not been treated with topical medications or shampoos;
avoid areas that are ulcerated, infected or traumatized;
sample multiple sites if possible
Use adequate pressure for scraping: apply gentle
pressure for superficial scrapes and firm pressure for
deep scrapes; scrape until capillary oozing occurs for
deep scrapes; do not cut or damage the skin with the
blade
Use enough mineral oil for scraping: lubricate the blade
and the slide with mineral oil before scraping; mix the
collected material with mineral oil on the slide; use
enough oil to cover the slide but not too much to
overflow
Examine the slide thoroughly: scan the slide in an
orderly fashion under low magnification; look for
parasites in different stages of development; move to
higher magnification for confirmation or identification;
use a reference guide or atlas for comparison
15. Conclusion:(finally!)
Skin scraping is an
invaluable diagnostic
tool in veterinary
medicine.
Identifies parasites,
skin diseases, and hair
loss in dogs and cats.
Benefits: Simple, cost-
effective, and rapid
with immediate results.
Techniques:
Superficial and deep
skin scraping.
Limitations: Variable
results, possible false
negatives and
positives, slight risk of
discomfort.
Tips for success:
Select appropriate
sites, apply right
pressure and oil,
conduct thorough
examination.
Skin scraping remains
reliable for
demodicosis diagnosis
in dogs and cats.
