SAQs

Question 1

Summary of neoplasms of the skin (7)

Answer 1

Question 2

Responses to injury (5)

Answer 2

Question 3

Dermal Patterns (6)

Answer 3

• 1). Perivascular dermatitis - least specific pattern of inflammation, most common, primary cause = hypersensitivity reaction (allergy = eosinophils).
• E.g. Flea allergy dermatitis, canine atopic deramtitis, malassezia dermatitis, sarcoptic mange.
• 2). Small vessel vasculitis - inflammation targeting walls of venules or arterioles.
• E.g. Diamond skin disease in pigs (Erysopelothrix rhusiopathiae), ischaemic areas of skin.
• 3). Interface dermatitis - cell-poor interface pattern (fewer cells present) or cell-rich (lichenoid pattern), always immune - auto + immune-mediated diseases.
• Lupus - e.g. discoid lupus erythematosus
• 4). Folliculitis - bacteria, fungi, parasites
• 5). Nodular dermatitis - nodules or diffuse sheet-like infiltrates of inflammatory cells in dermis/subcutis.
• E.g. Nodular = feline leprosy, caused by mycobacterium; diffuse = Leishmania.
• 6). Vesicular + pustular dermatitis - vesicle in different locations, due to bacterial, fungal, immune-mediated or viral disease + parasites.
• E.g. FMDV.

Question 4

Neoplasms of the skin (7)

Answer 4

Question 5

Describe the pathogenesis of folliculitis and furunculosis (8)

Answer 5

• 1). Infectious agents enter hair follicle, feed off the hair as they like keratin
• 2). Inflammatory cells start to gather nearby - perivascular inflammation
• 3). Inflammatory cells penetrate into the lumen of the follicle - perifolliculitis
• 4). Mural folliculitis - inflammation is within the wall of the follicle
• 5). Luminal folliculitis - inflammatory cells have entered the lumen where the infectious agent is
• 6). Wall of follicle is weakened by enzymes produced by inflammatory cells - furunculosis
• 7). If severe enough, can result in draining tracts away from original lesion
• 8). This can then result in crusting - v common in furunculosis

Question 6

Burrowing vs non-burrowing mites (4)

Answer 6

Burrowing:

• Have shorter legs
• E.g. Sarcoptes, Demodex

Non-burrowing

• Have longer legs
• E.g. Psoroptes, Chorioptes, Otodectes

Question 7

Hard vs soft ticks (13)

Answer 7

Hard:

• (Ixodidae) - have a chitinous dorsal plate (scutum) and visible mouthparts, most common in UK
• Blood feeding at each stage in lifecycle - attaches and feeds
• Temporary ectoparasites - once fed (1-2 weeks), will drop off and live in environment
• Adult female feeds to obtain protein in blood for her eggs, swells to 2-3 times original size.
• Inactive in winter, active to feed in spring and early summer, activity reduces peak summer (drier) and second peak in autumn.
• E.g. I. ricinus (‘castor bean’ or sheep tick) and I. hexagonus (hedgehog tick)
• Transmit diseases e.g. babesiosis, Lyme disease (Borrelia), tick pyaemia, erlichiosis

Soft:

• (Argasidae) - no scutum and can’t see mouthparts from above
• Undergo one larval stage and several lymph stages, taking small feeds from many animals when the opportunity arises
• Mostly active at night
• Live mainly in the host’s pen/nest
• More drought tolerant than hard ticks
• E.g. Argas sp. of birds