Dermatological diagnostics & interpretation

Question 1

Describe the white paper test.

Answer 1

To look for flea dirt in order to prove flea infestation.

Wet the paper. Comb the animal and put all the hair and dirt on the white paper. Flea dirt consists of ingested blood - will torn to brownish red on the paper.

This test doesn’t work so well on cats because they groom so thoroughly. Always do treatment trial on cats.

Question 2

Describe using a Wood’s lamp.

Answer 2

To diagnose dermatophytosis.

Only 50-90% of Microsporum canis will florescence so you can’t rule out the disease.

A Wood’s lamp is a UV-lamp. Let it warm/your eyes to adjust.

Shows an Apple-green color on the hair!
Wrong positives can be caused by creams, crusts, keratin…

Question 3

Describe Fungal cultures.

Answer 3

Using DTM (Dermatophyte test medium).

Sabouraud agar or Sabouraud dextrose agar (SDA) is a type of agar growth medium containing peptones. It is used to cultivate dermatophytes and other types of fungi, and can also grow filamentous bacteria.

Trichogram/Scrape/McKenzie sample taking by using new toothbrush, brush the animal or lesion (if lesional). Press the medium 5-6 times.

Colonies should appear in 14 days in untreated animal.

Inspect daily. Both colony and color change should happen simultaneously. Keep in Dark room. Check daily!

If suitable colony - you need microscope it (Roth).
False-positives in fomite carriers, false negatives if not enough material.

Question 4

What is the mckenzie technique for fungal culture?

Answer 4

a method used to collect samples for fungal culture

A fresh, unused toothbrush or a sterile brush is used to collect fungal spores and hairs from the coat of the animal. thoroughly brushed for about 2-3 minutes.

The brushing is done all over the body, even if no lesions are visible, as the animal may still be carrying the fungus asymptomatically.

The toothbrush or brush is pressed onto the fungal culture medium (e.g., DTM or Sabouraud dextrose agar) about 5-6 times to transfer spores.

Question 5

Answer 5

neg

no colony no color change

Question 6

neg or pos?

Answer 6

neg

color change and colonies but they are grey so thats just environmental contamination. dermatophytes make fluffy white colonies.

Question 7

pos or neg?

Answer 7

no color change

colonies yes but needs agar color change as well to be pos

Question 8

neg or pos?

Answer 8

contamination due to grey color

dermatophytes grow white colonies

if youre suspicious do cytology

Question 9

neg or pos?

Answer 9

pos for dermatophytes

fluffy white colonies with agar color change

Question 10

whats this

Answer 10

Diascopy: Press the glass slide on the
skin to tell Erythema from hemorrhage

In this pic: erythema multiforma due to drug reaction

Question 11

Describe Bacterial cultures.
When should you culture? (5)

Answer 11

Must differentiate normal microbiota vs cause of the disease.

When should you culture?
1. rod shaped bacteria on cytology
2. empirical treatment doesn’t work
3. suspicion of resistance (post-operative infections, non-healing wounds, multiple or recent courses)
4. life-threatening infections
5. (furunculosis - other deep infections that require 4-6 week AB treatment duration)

staph. intermedius is one of most common pathogenic bacteria

Question 12

How to culture?

Answer 12

Primary lesions (like fluid from pustules) vs under the crust/border of an epidermal colarette.

Sterile procedure, don’t contaminate. Try and aspirate pustules to get the contents onto a slide.

Swabs vs biopsy (like in deep infections)

Disc infusion vs MIC for sensitivity testing.

Typically discontinue the antibiotics for sampling for at least a few days. If not, let the lab know that the animal has been on AB.

Question 13

Describe Skin scrape/trichogram. (6)

Answer 13

• Glass slide + paraffin oil + sample+ cover slide
• not stained
• use low magnification - 5x 10x lens
• close the diaphragm/condensor (gives higher contrast to your sample)
• the lens is NOT to come into contact with the oil
• this is for large things like hair, parasites

Question 14

Describe Cytology. (8)

Answer 14

• Glass + sample + immersion oil
• STAINED
• strong magnification 100x
• open diaphragm/condensor
• clean the 100x lens with alcohol swab after use!
• for viewing small things like cells, bacteria, malassezia
• Info about inflammation (neutrophils, eosinophils, macrophages). Inflammation can be sterile (even with
  pustules)
• Eosinophils in cats and dogs with furunculosis/ autoimmune disease.

Tape strip, direct smear, indirect smear via swabs, FNA

Most skin diseases usually have primary disease + secondary infections!

Question 15

What can we find on skin/ear cytology?

Answer 15

• Keratinocytes
• Bacteria, yeast
• Neutrophils and other inflammatory cells
• 0 (WNL) up to 3+
• Neoplastic cells
• Artefacts
• Direct smear
• Indirect smear (cottin q-tip etc)
• FNA

Tape strip, direct smear, indirect smear via swabs, FNA

You should not have neutrophils on your skin normally, especially cells that have phagosytized bacteria (visible on microscopy).

Question 16

What are good options to take sample from interdigital region?
Folds of pug?
Crusts on the back?

Answer 16

tape

swab/ q-tip

lift crust up with slide edge then do direct impression smear with slide

Question 17

Answer 17

mostly rods, some cocci here and there

tx with local AB ear drops

cocci are smaller than rods and are really round

Question 18

Answer 18

mostly rods, some cocci here and there

Question 19

Answer 19

malassezia 3+

Question 20

Answer 20

rods

biofilm clusters can be seen, needs to be cleaned out

Question 21

What compound can be used to break up biofilm in ears?

Answer 21

acetylcysteine

tris-nac contains this, similar to triz aural

Question 22

Answer 22

broken cells maybe neutrophils

Question 23

Answer 23

epithelial acanthocytes or acantholytic cells (a type of kertinocyte)

neutrophils in the background

“Acantholysis is the loss of cohesion between keratinocytes as a result of dissolution of intercellular connections.”

very typical to pemphigus foliaceous case which this is. the most common autoimmune disease in small animals.

Question 24

Answer 24

leukocytes

neutrophils
lymphocytes (almost no cytoplasm)
macrophages (have cytoplasm space, suspect infection when they are present)

Question 25

Answer 25

demodex

Question 26

How to confirm dermatophytosis?

Answer 26

Use the Roth method! a tape impression method for diagnosing dermatophytosis (ringworm) by detecting macroconidia (a type of fungal spore) on hair shafts. the tape is stained.

Question 27

Artefacts on cytology - what to ignore? (6)

Answer 27

* Melanin granules * Spores of molds (Alternaria) * Plant pollen * Conchiformibius spp (Simonsiella) (normal microbiota bacteria) * Fibers (textile) * Medication (ears)

Question 28

Answer 28

Conchiformibius (Simonsiella) the bacteria paakut that look like jumbo bacteria or even vaguely like jumbo yeast are actually normal microflora of the mouth. If seen, indicates licking, due to e.g. pruritus!

Question 29

Answer 29

Molds Alternaria spp. environmental contamination you may see on cytology

Question 30

Answer 30

reeeally teeny, smaller than bacteria even cocci Differentiating melanin granules from cocci bacteria in a skin cytology sample can sometimes be challenging, as both can appear as small, dark, round structures. cocci are perfectly round and uniform, melanin granules can be irregular in size and shape. cocci are often found in pairs, clusters or chains and can be intracellular inside neutrophils. melanin granules are usually diffusedly scattered and often seen within melanocytes, macrophages or keratinocytes rather than free floating. cocci stain either dark purple if gram pos. or pinkif gram neg. melanin does not stain with gram stain, may appear black or brown with diff-quik.

Question 31

Answer 31

that big dark cylinder is pollen (image also has malassezia) ## Footnote dont mistake it for a parasite egg.

Question 32

Answer 32

Plant pollen 100X lens, NOT parasite eggs

Question 33

Answer 33

crystals caused by ear medication super sharp edged compared to e.g. urine crystals

Question 34

Describe Trichograms.

Answer 34

You can tell Anagen (active growth) vs telogen (resting phase) by looking at the hair in microscopy. Trichograms are for finding Parasites, dermatophytes. Melanin clumps (color dilution alopecia) may be seen. (melanin clumping refers to the abnormal aggregation of melanin pigment within hair shafts and follicular cells. This occurs due to defective melanin distribution in dilute-colored coats). Tips of hair may show if traumatized - licked, broken? Follicular casting (can indicate infections) ## Footnote follicular casts just means keratin accumulation-inflammation

Question 35

Answer 35

skin mites

Question 36

Describe Allergy skin testing/ serum testing.

Answer 36

NB Can not be used to diagnose allergies! Is used for therapy: allergen specific immunotherapy. Animal must be weaned from corticosteroids before doing! ## Footnote Plain histamine is used for the positive control, plain NaCl is used for the neg one.

Question 37

Describe Skin biopsies - histopathology.

Answer 37

Diagnostic method in case of suspicion of immune-mediated or autoimmune disease, acute diseases, in case of tumor (also non-healing wounds), non- responsive diseases, weird presentation. Autoimmune diseases (before immunosupressive treatment) To diagnose some specific diseases (zinc responsive dermatitis, follicular dysplasias, alopecia x, herpes dermatitis). 1 biopsy is not enough! Take multiple. NB This is not a sterile surgery! ## Footnote Choose a pathologist with interest in dermapathology Give the pathologist all the history. Add your differential diagnoses!

Question 38

zinc responsive dermatitis is

Answer 38

seen in some small animals, particularly in dogs. primarily caused by a zinc deficiency or the body's inability to properly absorb zinc, leading to skin lesions, inflammation, and other dermatological issues. so deficiency + genetic factors + inhibitoes of zinc absorption common signs: erythema, scaling/crusting, alopecia, lesions, itching commonly on face, paws, groin, underbelly Blood Tests: Zinc levels may be measured to confirm a deficiency. ## Footnote supplement zinc, adjust diet, topical tx to sooth skin, address 2ndary infections

Question 39

follicular dysplasias

Answer 39

Follicular dysplasia in small animals refers to a genetic or developmental disorder affecting hair follicles, leading to abnormal hair growth and hair loss. This condition typically results in thinning or patchy hair, often with the appearance of bald spots, and is most commonly seen in certain breeds such as the Chinese Crested, Mexican Hairless, and Dachshund. Follicular dysplasia may cause various skin issues like excessive shedding, hyperpigmentation, and secondary infections due to impaired hair follicle function. It can be inherited, and while there is no cure, management often involves controlling symptoms with supportive care, such as moisturizing the skin, using medicated shampoos, and addressing secondary skin infections.

Question 40

alopecia x

Answer 40

Alopecia X, also known as "coat color dilution alopecia," is a hereditary skin condition primarily affecting dogs, particularly certain breeds like the Pomeranian, Chow Chow, and Keeshond. It is characterized by the progressive loss of hair, starting from the trunk and often affecting the hindquarters, tail, and neck. Despite the hair loss, the skin typically remains healthy, and there is no significant itching or inflammation. The condition is thought to be related to hormonal imbalances, particularly involving the adrenal or pituitary glands, though the exact cause is still unclear. While it does not cause discomfort, it can be a cosmetic concern for pet owners, and management options may include hormone therapy or other treatments to stimulate hair regrowth, though there is no definitive cure.

Question 41

herpes dermatitis

Answer 41

Herpes dermatitis in small animals is a viral skin infection caused by the herpesvirus, most commonly seen in cats (feline herpesvirus) and occasionally in dogs. This condition typically results in the formation of lesions, ulcers, or crusts on the skin, often around the face, eyes, and nose. Infected animals may also exhibit symptoms like conjunctivitis, nasal discharge, and lethargy. While herpes dermatitis is not typically life-threatening, it can cause significant discomfort, and treatment generally focuses on managing symptoms with antiviral medications, supportive care, and maintaining a healthy immune system to prevent flare-ups. In some cases, secondary bacterial infections may also require treatment.

Question 42

skin mites to affect cats? (4)

Answer 42

Ear Mites (Otodectes cynotis) Demodex Mites (Demodex cati and Demodex gatoi) Cheyletiella spp. Sarcoptes scabiei

Question 43

describe flea allergy dermatitis

Answer 43

Flea allergy dermatitis (FAD) is a common skin condition in small animals, particularly in dogs and cats, caused by an allergic reaction to flea saliva. When a flea bites, it injects saliva into the skin, triggering an immune response in sensitive animals. This leads to intense itching, redness, inflammation, and secondary skin infections. The most common areas affected are the back, tail base, and hindquarters. Affected animals may excessively scratch, bite, or lick at the skin, which can lead to hair loss, scabs, and sores. Flea allergy dermatitis is often diagnosed based on clinical signs and flea presence, and treatment involves controlling flea infestations through regular flea prevention, medicated shampoos, and sometimes antihistamines or corticosteroids to manage inflammation and itching.