Introduction to equine derm

Question 1

Describe type 1 hypersensitivity - give horse example

Answer 1

IgE mediated involving the release of histamine by mast cell.

e.g. Insect-bite hypersensitivity AKA Sweet itch

Question 2

Describe type 2 hypersensitivity - give a horse example

Answer 2

IgG mediated cytotoxic response associated with complement binding.

e.g. Pemphigus complex

Question 3

Describe type 3 hypersensitivity- give a horse example

Answer 3

Immunocomplex deposition on endothelial beds

e.g. Pastern leukocytoclastic vasculitis, purpura haemorrhagica, Lupus..

Question 4

Describe type 4 hypersensitivty- give a horse example

Answer 4

T- cell mediated.
e.g. Insect-bite, drug eruptions

Question 5

if skin lesions are on mane, tail and ventral line what is a likely cause

Answer 5

insect-bite hypersensitivity

Question 6

if skin lesions are on base of tail- list 3 possible causes

Answer 6

Oxyuris equi AKA pinworm
Insect-bite hypersensitivity
Lice infestation (normally more truncal)

Question 7

If skin lesion on group, chest, neck and sometimes face- name a possible cause

Answer 7

fungal infection

Question 8

If skin lesions affect back, chest, rump and sometimes face- what is a likely cause

Answer 8

rain scald

Question 9

if skin lesions affect distal limbs- list 2 possible causes

Answer 9

“Mud fever” : bacterial ± fungal
Mite infestation: Trombiculiasis, chorioptic mange

Question 10

If skin lesion affects truncal, neck and occasional head- list 3 possible causes

Answer 10

urticarias
atopia
lice infestation

Question 11

If skin lesions affect back and girth area- list 2 possible causes

Answer 11

contact dermatitis
fungal infection s

Question 12

List 10 skin lesions that are defined as primary

Answer 12

macule
patch
papule
plaque
vesicle
pustule
wheal
nodule
tumour
abscess

Question 13

List 7 skin lesions that we define as secondary lesions

Answer 13

alopecia
scale
crust
erosion
ulcer
lichenification
hypo/hyperpigmentation

Question 14

what are coat brushing good to diagnose

Answer 14

ectoparasites

Question 15

what can skin scrpaes be used to diagnose

Answer 15

mites
dermatophytes

Question 16

what are skin biopsies ideal for

Answer 16

nodules and deep pyodermas
culture and histolog

Question 17

what can acetate tape be used to diagnose

Answer 17

Oxyrus equi eggs

Question 18

what causes rain scald

Answer 18

Dermatophilus congolensis

Question 19

what are the 2 types of allergy tests in horses

Answer 19

serum (SAT)- poor sensitivity
intradermal (IDT)- better diagnostic yield

Basically neither of them are very good so not done often

Question 20

what does hair coat shedding depend on

Answer 20

daylight hours- melatonin and prolactin driven