Equine dermatology Flashcards
what should be obtained from a general history?
age gender breed colour management feed
what is a common skin condition seen in young horses that will disappear over time?
papilloma
what should be discussed with regards to the management when obtaining a history?
other horses present other animals stabling feeding work
with regards to the history of the current problem, what needs to be determined?
when it started
has it improved or gotten worse - changes? treatment?
what has been done to treat it - results? duration?
with regards to the lesions present, what needs to be established?
type
distribution
extent/severity
whether it is primary/secondary
what ways can samples be collected on a primary basis? (simple)
skin brush/scrape
hair pluck
adhesive tape
skin biopsy
what ways can samples be collected on a secondary basis? (second stage)
skin biopsy
intradermal skin test
blood test
what is skin brushing good for looking for?
parasites
what are hair plucks useful for looking for?
lice eggs - white dots
what are the reasons to do a skin biopsy?
if there are papules or pustules
neoplastic lesions
when is skin biopsy not useful?
immune-mediated and autoimmune disorders
ulcers and crusts
chronic lesions
what are the golden rules for skin biopsies?
try not to clip
do not scrub the skin
place small amount of local anaesthetic subcutaneously
rotate biopsy punch in one direction
what areas should a skin biopsy not be taken from?
over the coronary band
define pruritus
unpleasant sensation that provokes the desire to scratch/itch
what are the two things that make horses pruritic?
parasitic skin disease
hypersensitivity (allergies)
what is the most common louse found on horses?
Werneckiella
where on the horse is Werneckiella found?
dorsolater trunk
neck
face
what type of louse is Werneckiella?
biting
what does Werneckiella feed on?
epidermal debri
what sucking louse is seen on horses?
Haematopinus asini
where is Haematopinus asini seen on the horse?
mane
tail
fetlock
pastern
what does Haematopinus asini feed on?
blood (sucking louse)
what horses is Werneckiella seen in?
housed younger/older houses in the winter
how are lice transmitted?
direct/indirect contact
how can lice be diagnosed?
coat brush or hair pluck
what can be used to treat lice?
pyrethrins, pyrethroids, permethrin, fipronil
where is Chorioptes equi found on the horse?
distal limbs
what is the major clinical sign of Chorioptes equi?
intense pruritus with stamping/scratching/chewing of feet
what is a common clinical sign of Psoroptes equi in horses?
headshaking - mite present in ears
how can mites be diagnosed?
skin brushing
what can be used to treat mites?
inject macrocyclic lactones
topical macrocyclic lactones
topical shampoos - lime sulphur, selenium sulphate, topical ivermectin
when do injectable MLs need to be administered to treat mites?
2 injections 2 weeks apart
how often do topical MLs need to be administered to treat mites?
once every 4 weeks
what is the name of the poultry mite that can effect horses?
Dermanyssus gallinae
where on the body does the poultry mite effect the horse?
head and legs
what are some nematodes that can cause pruritus in horses?
Oxyuris equi
habronemiasis
Onchocerca cervicalis
what is Oxyuris equi also known as?
pinworm
what body area does the pinworm cause pruritus in?
perianal
what is used to treat Oxyuris equi?
anthelmintics - none specifically designed for Oxyuris
what is habronemiassis spread by?
flies that lay their larvae under the skin
what season is habronemiassis seen in?
spring/summer
what are the clinical signs of habronemiassis?
ulcerative nodules
granulation tissue with yellow granules
what can be used to treat habronemiassis?
ivermectin
corticosteroids - control hypersensitivites that may develop when larvae die under the skin
where do adult Onchocerca cervicalis live?
nuchal ligament
how can Onchocerca cervicalis cause hypersensitivity?
microfilarie migrate to the skin surface
what season is Onchocerca cervicalis worst?
spring/summer
where on the horses body is Onchocerca cervicalis usually seen?
face, neck, ventral chest, abdomen
what can be done to treat Onchocerca cervicalis?
ivermectin
corticosteroids - protect against potential hypersensitivity reaction caused by the death of the worm
what are the hypersensitivities that can be seen in horses?
insect hypersensitivity food allergy contact allergy atopy urticaria
where on the animal is insect bite hypersensitivity seen?
main, back, tail ventrum
what are the risk factors that can increase the likelihood of insect bite hypersensitivity?
standing water
dusk/dawn
what are the clinical signs of food allergy?
pruritus
diarrhoea
respiratory disease
how are food allergies diagnosed?
diet elimination
what is done do diagnose atopy?
exclusion
intradermal skin testing can be helpful
what can be done to teat atopy?
avoid allergen
immunotherapy
corticosteroids/antihistamines
improve skin barrier function
what are the clinical signs of urticaria?
wheals
oedema
pruritus
what is urticaria also known as?
hives
what can be used to treat urticaria (hives)?
corticosteroids
antihistamines
what are some common skin diseases that cause crusting, scaling erosion and/or ulceration?
dermatophilosis (rain scald) bacterial folliculitis dermatophytosis (ringworm) photosensitisation leukocytoclastic vasculitis pastern dermatitis pemphigus foliaceous
what bacteria causes dermatophilosis?
Dermatophilus congolensis
what is dermatophilosis also known as?
rain scald
describe the bacteria Dermatophilus congolensis
gram positive
facultative anaerobe
what factors causes dermatophilosis?
chronic moisture
skin damage
describe the lesions associated with dermatophilosis
crusts
moist mats of hair
where on the body is rain scald seen?
back, gluteal area, face, neck extremities
how can dermatophilosis be diagnosed?
cytology using a pus smear
what can be used to treat dermatophilosis?
topical antimicrobials (mild cases) systemic antimicrobials (severe cases)
what bacteria can cause bacterial folliculitis?
Staphylococcus
Streptococcus
how can bacterial folliculitis be diagnosed?
cytology and culture
what is used to treat bacterial folliculitis?
topical and systemic antimicrobials depending on severity
what is dermatophytosis more commonly known as?
ringworm
what causes the pruritus in pinworm infections?
the substance used to glue the eggs onto the outside of the anus
how can Oxyuris equi be diagnosed?
clinical signs and tape strip
why are ticks a worry in horses?
due to the transmission of disease - lyme disease, babesiosis…
what can be used to treat tick infestations?
fipronil spray
ivermectin
topical pyrethroids
what is another name for insect bite hypersensitivity?
sweet itch
what it insect bite hypersensitivity a hypersensitivity to?
female Culicoides spp. saliva
how can insect bite hypersensitivity be treated?
avoid midge contact - fly repellents and rugs
reduce immune reaction - steroids (can lead to laminitis)
what is hives?
small patches of oedema under the skin surface
what does scaling looking like?
it is seen as dry and grey
what is the appearance of crusting?
yellow, red and brown
usually wet and damp
from serous ooze
what is the difference between erosion and ulceration?
erosion is superficial and ulceration is deep
what are the characteristics of bacterial folliculitis lesions?
pain
oozing/wheeping lesions
what are the two most common fungi that cause ringworm in horses?
Trichophyton and Microsporum
what horses is dermatophytosis most commonly seen in?
young and immunocompromised
what do the lesions of dermatophytosis look like?
circular well demarcated patches of alopecia with an ashy appearance
how can ringworm be diagnosed?
fungal culture, PCR, microscopy
what is used to treat ringworm?
topical antfungals - miconhzole, natamycin
what are the two possible causes of photosensitisation?
hepatogenous - liver failure…
ingestion or application of photodynamic agent
on what areas of skin is photosensitisation most common?
areas of white hair
what is used to treat photosensitisation?
treat liver disease
removal of photodynamic agent
what lesion could be linked to photosensitisation?
leukocytoclastic vasculitis
where does leukocytoclastic vasculitis effect?
the lateral distal limbs of horses (white hair)
what can be done to diagnose leukocytoclastic vasculitis?
clinical signs
skin biopsy
what can be done to treat leukocytoclastic vasculitis?
avoid exposure to light
corticosteroids
what is meant by pastern dermatitis?
a skin condition seen on the pastern - can have many causes
what type of disease is Pemphigus foliaceous?
autoimmune disease
what is the major clinical sign of Pemphigus foliaceous?
severe crusting
what is used to treat Pemphigus foliaceous?
immunosuppressive drugs (steroids)
what are the most common cutaneous swellings, nodules and tumours seen in horses?
viral papillomatosis warbles genetic/developmental eosinophilic granuloma tumours - sarcoid, melanoma, squamous cell carcinoma...
what are two examples of viral papillomatosis?
grass warts
Pinnae Acanthosis
what is the treatment of grass warts and pinnae acanthosis?
no need to treat, regress on their own and is purely cosmetic
what are the species of warbles that cause nodules on the skin?
Hypoderma bovis and lineatum
what is used to treat warbles?
ivermectin
surgical removal
what nodular skin condition is notifiable?
warbles
what are some genetic/developmental skin masses/nodules?
dentigerous cyst
atheroma
dermoid cyst
vascular hamartoma
what is a dentigerous cyst?
small cyst of an embryonic remanent around the head area of the house, often containing teeth or hair
what is an atheroma?
a growth on the inside of the false nostril - don’t normally cause problems but can be removed because of cosmetics
what can cause an eosinophilic granuloma?
hypersensitivity reaction to insect bites, trauma or anything else causing necrosis of collagen
what are some common skin tumours?
sarcoid
melanoma
squamous cell carcinoma
what are sarcoids made of?
fibroblasts
what are thought to be possible risk factors/causes of sarcoids?
bovine papillomavirus 1/2
genetic predisposition
flies
how many clinical presentations of sarcoids is there?
6
what are the 6 clinical presentations of sarcoids?
occult verrucose nodular fibroblastic mixed malignant
describe an occult sarcoid
alopecic faded area of skin that turns scaly/dark
describe a verrucose sarcoid
alopecic faded area of skin that turns scaly/dark with a lumpy/warty appearance
describe a nodular sarcoid
small growths under the skin
how can sarcoids be diagnosed?
biopsy
clinical presentation
why should care be taken when taking a biopsy of a sarcoid?
can exacerbate then - be prepared to treat quickly
what can be used to treat sarcoids?
brachytherapy surgery/laser removal cytotoxic photodynamic therapy (lots of therapies because none of them work very well)
what are the general rules for sarcoid prognosis?
more they have the more they get
multiply over summer and grow in winter
single sarcoid indicates genetic susceptibility
what horses are melanoma most common in?
grey horses over 15 years old
where are most melanomas located in horses?
perineum, tail head, parotid region
can appear anywhere
are melanomas benign or malignant?
mostly benign but some are malignant
how care melanomas diagnosed?
clinical signs and biopsy
what can be done to treat melanomas?
surgical excision - sooner rather than later
immunotherapy
where do squamous cell carcinomas commonly grow on horses?
external genitalia
eye
(other locations possible)
how are squamous cell carcinomas treated?
surgical excision
cryotherapy
chemotherapy
where are cutaneous lymphomas most commonly seen on horses?
trunk and neck
