If you are looking for Demodex canis mites on a dog, do you want to do a superficial or deep skin scraping?
Deep
Demodex mites live deep in the hair follicles.
Which mechanism of skin disease of small animals is typically responsible for lesions on the nasal planum, pinnae, and foot pads?
Immune-mediated skin disease
If you are looking for Sarcoptes mites, do you perform a deep or superficial skin scraping?
Superficial
Acantholysis is noted on a skin biopsy. What is the most common cause of this finding?
Autoimmune disease
e.g., pemphigus
What is the pinnal-pedal reflex and which disorder does it suggest?
It is the vigorous scratching motion performed with the hindlimb, typically by dogs
(in response to gentle rubbing of the ipsilateral pinna)
It is a sign of intense pruritus, and is most commonly associated with sarcoptic mange (seen in 80% of cases vs. in 7% of other causes of pruritus).
What is the expected change in appearance of a plate containing a specimen of hair on dermatophyte test medium if a positive result occurs?
The medium turns from clear yellow to deep red in approximately one week
After 10 days, false positive results are possible due to saprophytes.
Intradermal skin testing for Mycobacterium bovis is an example of what type of hypersensitivity reaction?
Type IV hypersensitivity, which is cell-mediated hypersensitivity
(a.k.a. delayed-type hypersensitivity)
In dermatology, what is the difference between a papule and a macule?
- Papule: a small, solid elevation of the skin ≤ 1 cm in diameter (i.e., a pimple, but without pus [which would make it a pustule])
- Macule: a circumscribed, nonpalpable spot of skin pigmentation ≤ 1 cm in diameter (i.e., a freckle)
Define:
Telogen defluxion
Loss of hair occurring one to three months after a stressful event
(e.g., pregnancy/parturition)
The event causes a sudden termination of growth of many anagen hair follicles, then synchronization of these follicles in catagen and ultimately telogen.
What is the name of the cutaneous manifestation of anaphylaxis consisting of pruritic wheals?
Urticaria
(hives)
Wood’s lamp examination is fast and inexpensive when searching for dermatophytosis; however, its major disadvantage is what?
Poor sensitivity
Has high specificity, but a negative test does not rule out disease (low sensitivity).
What is the clinical significance of a fractured hair shaft on microscopic examination of a hair specimen?
Indicates external trauma
(e.g., excessive licking or scratching)
This narrows the differential diagnoses by ruling down endocrine and other atraumatic causes of alopecia, and making allergies/ectoparasites/etc. more likely.
What is the most common cause of fungal infection of the nail (onychomycosis) in dogs? What is it in cats?
- Dogs: Trichophyton mentagrophytes
- Cats: Microsporum canis
Malassezia spp. and candidiasis (yeast) less common in both.
Name three cutaneous manifestations of hepatic failure.
- Icterus
- Superficial necrolytic dermatitis*
- Photosensitization
- Petechiae/ecchymoses/bruising
- Poor wound healing
- Pruritus
*Also called necrolytic migrating erythema and hepatocutaneous syndrome.
Which mite is a normal commensal organism on the skin?
- A. Sarcoptes
- B. Cheyletiella
- C. Demodex
- D. Notoedres
- E. None of the above
C. Demodex
Demodex are normal commensals in the hair follicles and sebaceous glands of mammals.
What bacterium causes these conditions: rainrot in horses, lumpy wool in sheep, and strawberry foot rot? And what are the predisposing factors for infection?
Dermatophilus congolensis
Predisposing factors are young age, chronic exposure to moisture, and immunosuppression.
Culicoides spp. cause insect bite hypersensitivity in horses. What is the typical distribution of lesions?
- Dorsal midline
- Mane
- Tailhead
- Ventral midline
i.e., especially in areas accessible to the biting midges
What causes the characteristic “diamond‑shaped” skin lesions seen in acute erysipelas in pigs?
The bacteria trigger vasculitis and thrombosis in dermal blood vessels
(producing the characteristic diamond-shaped skin lesions)
A 10‑week‑old Landrace pig presents with asymptomatic, symmetrical raised red lesions on the ventral abdomen and inner thighs that expand outward to form ring‑shaped, scaly plaques. Other pigs with similar signs resolved without treatment.
What is the most likely diagnosis?
Pityriasis rosea
(also called porcine juvenile pustular psoriasiform dermatitis)
Characteristic ring‑shaped, self‑resolving plaques in young pigs with no other systemic signs.
What causes “greasy pig disease” in piglets, and how are the skin lesions described?
- Cause: Staphylococcus hyicus produces exfoliative toxins that disrupt superficial epidermis
- Lesions: Erythematous, greasy, moist exudate that crusts and darkens, often affecting face, ears, lips, and feet
What is the main difference between biting/chewing and sucking lice in animals?
- Biting/chewing lice feed on skin debris, hair, or feathers
- Sucking lice feed on blood
Lice species are classified by their feeding method, which influences clinical signs and severity of infestation.
Pox diseases affect many animals, and some are zoonoses. What are the lesions of pox diseases actually comprised of?
- A. Bacterial colonies in the dermis
- B. Accumulations of immune cells
- C. Intracytoplasmic viral inclusions in infected cells
- D. Fibrous scar tissue
C. Intracytoplasmic viral inclusions in infected cells
Poxvirus lesions form where the virus replicates inside cells, producing swelling, vesicles, and pustules.
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