Exam 1 - Equine Pruritus Flashcards
what is erythema/erythroderma? what does it typically indicate?
redness - inflammatory process
what is this lesion? primary or secondary?
macule/patch - primary
what is this lesion? primary or secondary?
papules - primary
typically less than 1 cm, represents cell infiltration
what is this lesion? primary or secondary? would you sample this?
pustule - primary, yes
what is this lesion type? what animal is it common in?
plaque - coalescing papules that you can palpate change in elevation
cats
what is the difference between a vesicle & bulla?
vesicle is a smaller version of a bulla
what is this lesion? primary or secondary?
vesicle/bulla - primary
what diagnostic test would you use for this primary lesion?
biopsy/culture
this is a nodule - has a large infiltration of cells that can be infectious, inflammatory, or neoplastic in nature
what is this primary lesion type? what animals commonly get these?
wheal/urticaria (hives) - horses
what is this lesion? primary or secondary?
epidermal collarette - secondary lesion
why are epidermal collarettes secondary lesions?
it is a ruptured pustule!!
what is this? how does it occur
erosion/ulcer
a vesicle/bulla ruptures - determined to be an erosion or ulcer by the depth of the lesion
what is the difference between an erosion & an ulcer?
an erosion is more superficial, is only epidermis, & heals without a scar
an ulcer crosses into the dermis & heals with a scar
what is this? what does its presence imply?
lichenification - implies chronicity & is commonly seen with hyperpigmentation
what is this lesion & how is it caused?
excoriation - self-induced version of an erosion/ulcer, typically seen in a linear fashion
what is this lesion? why can it be either primary or secondary?
scale
primary - animal has an inability to make normal skin
secondary - secondary to infection
what is this lesion? why can it be either a primary or secondary lesion?
crust
primary - autoimmune disease
secondary - ruptured pustule (scab)
what is this lesion?
crust
follicular casts can be primary or secondary & are commonly seen with what infection?
dermatophytosis
what is this?
follicular casts - paint brush appearance
what is this lesion? primary or secondary?
comedones - blackhead, plugged follicle that is oxidized
can be either primary or secondary
what is this lesion?
hyperpigmentation - primary (birthmark)
what is the difference in primary & secondary hyperpigmentation?
primary would be something like a birthmark or freckle
secondary - longterm problem, allergies/infection, can go away in time
how can hypopigmentation/depigmentation be a primary or secondary lesion?
primary - vitiligo (autoimmune)
secondary - disruption of the lower layers of the epidermis
why is it important to differentiate inflammatory alopecia from non-inflammatory alopecia?
inflammatory - hair is being pulled/scratched out
non-inflammatory - hair is falling out
helpful to indicate pruritic disease
what are the first 4 steps when approaching dermatological lesions in horses?
- what am I looking at?
- is it a primary or secondary lesion?
- what is the pattern?
- why is it here? need a sound history (pruritic or not)
what are some clinical signs of itching in horses that an owner may not notice?
tail twitching, stomping, rolling, & head shaking
what big 3 categories are you approaching dermatology cases with?
parasites, infections, & allergies
what is xeroderma?
dry skin
big 3 components for working up a pruritic horse?
history
clinical signs
physical examination
why is location so important when looking at dermatological lesions?
helps narrow down your differentials
what is your minimum database when starting a derm case?
parasite combing, skin scrape, anti-parasite trials/fly control, & skin cytology
if your minimum database doesn’t provide many results, what may you pursue diagnostically?
allergy trials
culture
biopsy
what are the two main categories that cause pruritic disease?
parasites & infection
when might you use a skin scrape?
suspect mites - get multiple sites including the feathers
if doing an impression cytology, what do you want to sample?
intact pustule or underneath a crust
what is the most common fungal infection seen in horses?
trichophyton
if doing a fungal culture in horses, what must you do for monitoring & what is required for growth?
monitor daily & keep for 21 days
needs B vitamins
what is pediculosis?
lice!!!!
what kind of lice is this?
biting - werneckiella equi
what kind of lice is this?
sucking - haematopinus asini
if I am concerned about my horse having biting lice, where should I look?
head, mane, & tail base - they loooove exfoliated skin cells & debris
if i’m scared my horse has sucking lice, where do I look?
head, neck, back, thighs, & fetlocks - they looove blood & tissue fluid
why is it good and bad that lice are species/host specific?
good because I can’t get them
bad because their horse/donkey friends will definitely get them because it is contagious
what season am I worried most about lice?
colder months
what animals do lice prefer?
young, old, & debilitated animals in over-crowded settings
what clinical signs may I see if my horse has lice?
variable pruritus, scaling, poor hair coat, alopecia, & anemia (rare)
why is this scary!
it’s LICE
why would you scream if you saw this?
it’s lice and there is no other reason needed
when considering ticks as the source of pruritus in a horse, this will be more of a _______ problem (focal/multifocal/diffuse)
focal
with most ticks being 3 host ticks, why does this make our lives more difficult?
parasite control becomes harder
this silly hat will help protect my horse from what tick?
otobius megnini - causes otitis externa
what clinical signs are commonly seen with otobius megnini?
head shaking, head rubbing, abnormal head carriage, seizures (rare), & ataxia (rare)
I have a bunch of itchy horses with distribution seen in the red….why am I concerned?
psoroptes equi!!!! a non-burrowing mite!!!!!!
how is psoroptes equi spread?
direct or indirect contact
T/F: ears are usually affected as well in psoroptes equi infections
true
why should you treat all in-contact animals with psoroptes equi?
10% of your herd????
if my horse is itchy in these locations……why am I scared?
SARCOPTES SCABEI!!!!!
can I get sarcoptes scabei?
yup! zoonotic!
what do I do immediately if my horse has sarcoptes scabei???
REPORT IT!!!! it’s eradicated in the USA
clinical signs of sarcoptes scabei?
INTENSE PRURITUS!!! severe disease :/
what kind of mite is sarcoptes scabei? (burrowing/non-burrowing)
burrowing
if this is where my horse is itchy, what am I thinking??
chorioptes equi!!! in my feathered draft breeds!
how is chorioptes equi spread?
direct or indirect contact - animals may be asymptomatic carriers
what season is chorioptes equi common in?
winter time
top differential?
chorioptes equi
what are the 3 mites you’re looking for when doing a skin scrape?
psoroptes, sarcoptes, & chorioptes
name that mite!
sarcoptes scabei
name that mite!
chorioptes!
name that mite!
psoroptes
what is the fancy name for chiggers?
trombiculiasis
‘papules with an orange dot in the center’ - describes what?
chiggers
dot = chigger larva
what seasons are chiggers more prevalent? what environments?
summer & fall
pasture, paddocks, & trails (tall grass)
why do chiggers cause itching?
the larvae feed on tissue fluid
this distribution is common for what small bug?
chiggers
between our 2 nematode parasites, which one causes pruritic signs & which one causes nodular lesions? (oncocerca cervicalis & habronema)
pruritus - oncocerca cervicalis
nodular lesions - habronema sp.
what is the pathogenesis of oncocerca cervicalis?
the wormies live in the nuchal ligament & produce microfilaria that migrate to the skin & are ingested by the intermediate host culicoides (biting midges)
this leads to non-seasonal pruritus that is highest in populations in the spring - causing idiosyncratic hypersensitivity reactions to microfilarial antigens
this lesion distribution is common in what nematode infestation
oncocerca cervicalis - cutaneous lesions associated with microfilaria deposition
with the prevalence of infection being high with oncocerca cervicalis, how should I treat this?
use ivermectin & moxidectin dewormers
T/F: only some horses will develop clinical signs with oncocerca cervicalis infestations & horses older than 4 years old are more likely to be having issues
true
what ocular lesions may be seen in oncocerca cervicalis infections?
sclerosing keratitis
vitiligo (bulbar conjunctiva)
white nodules (pigmented conjunctiva)
uveitis
depigmentation bordering the optic disk
what is a permanent change seen in oncocerca cervicalis infections?
leukoderma at the site of skin lesions
what is the fancy science name for pinworms??
oxyuris equi
this lesion distribution is commonly seen with what parasitic infection?
oxyuris equi - itchy ass!!!
how do horses get pinworms?
the ingest the eggs from their environment
what are the clinical signs seen with pinworms? what horses does it typically affect?
restlessness, irritability, itchy ass
stabled horses
if I suspect pinworms, what diagnostic test should I do? what would I expect to see?
tape prep!!
eggs on the tape prep of the perineum
what is this?
pin worms - oxyuris equi
T/F: differential diagnoses for pruritus in the horse regarding infections is generally secondary to something else
true
what are my big three differentials for pruritic infections in the horse?
bacteria, dermatophytosis, & malassezia
if I see an itchy horse with this lesion distribution, what am I thinking?
bacterial follicultis - staph spp. (s. aureus, delphini, pseudintermedius)
T/F: bacterial folliculitis is common & is often mistaken for dermatophytosis
true
if I suspect bacterial folliculitis, what is my first line of treatment?
TOPICALS!!!!!!!!! antiseptic therapy!!!!! this is a superficial bacterial problem
why is topical therapy important to use for bacterial folliculitis?
decreases organism adherence & numbers, mechanical removal of infectious debris, decreases the need for antibiotics, additional beneficial properties such as drying/soothing, & there is a greater chance for resistance to antibiotics than an antiseptic
what is the most common MRSA in dogs? horses? which one is a bigger concern?
dogs - s. pseudintermedius
horses - s. aureus
s. aureus - this is a people problem!!
T/F: malassezia dermatitis is historically under-reported in horses
true
what body areas are commonly affected in horses with malassezia problems?
skin folds!! causes a greasy-waxy exudate
what is this?
malassezia
what is the most common cause of equine pruritus??
insect hypersensitivity!!
T/F: insect hypersensitivity is usually a type 1 hypersensitivity that is mediated by IgE & may progress to a type IV hypersensitivity
true
what are the 3 bugs i’m thinking about when it comes to insect hypersensitivity?
flies, mosquitoes, & culicoides
why does it matter that I know what bug is affecting my horse?
controlling the insects causing the problem will control my insect hypersensitivity problem!
how do I know what insect is causing my horse problems??
-feeding location preferences
- time of day for feeding
-environmental requirements
what is the lesion distribution for gnats (culicoides)?
dorsum, ventrum, face, & ears
what bug causes this lesion distribution??
culicoides!
what bug is the most common cause of insect hypersensitivity?
culicoides!!
what is the feeding time for culicoides?
twilight to dawn
what environment is needed for culicoides?
STANDING WATER, manure, & vegetation
T/F: big fans in stables can help with a culicoides problem because they are weak fliers
true
what are common names for culicoides problems?
queensland itch & sweet itch
what is the lesion distribution for mosquitoes?
ventral midline, lower limbs, & may be generalized
what bug causes this lesion distribution?
mosquitoes
what is the feeding time for mosquitoes?
feed dusk to 2 hours past sunset
what is the environment for mosquitoes?
water
what bug causes this lesion localization?
horse flies - tabanus
what is the lesion distribution for horse flies?
ventral midline, neck, ears, lower limbs, & generalized all over because they are mean
what time of day do horse flies feed?
daytime
what is the environment for horse flies?
vegetation & water
like the horse flies, this fly also has a lesion distribution of ventral midline, neck, ears, lower limbs, & generalized all over. what is it?
deer fly - chrysops
what is the feeding time for deer flies? environment?
daytime
vegetation & water
what fly is generally associated with the presence of cattle? why?
horn flies - haematobia
they loooove poop in their environment
what fly causes this lesion distribution?
horn flies
what is the lesion distribution for horn flies?
ventral midline
what time of day do horn flies feed?
daytime
what fly has an environment of rotting vegetation?
stable flies - stomoxys
what time of day do stable flies feed?
daytime
what is the lesion distribution of stable flies?
dorsum, ventrum, midline, neck, & lower limbs
what fly causes this lesion distribution?
stable flies
what fly causes this lesion distribution?`
black flies - simulium
what is the lesion distribution of black flies?
face (especially ventral chin), ears, & ventral midline
what is the feeding time for black flies?
morning & evening feeders
what environment is needed for black flies?
RUNNING water
how can I improve my management of insect control in regards to my horse’s environment?
clean it up!!
remove decaying vegetation, manure, & standing water
how can I improve my management of insect control in regards to my changing my horse’s environment?
use fans in stalls, mesh guards, move them away from cattle, & move from pasture to stable in consideration of feeding times
how can I improve my management of insect control in regards to my horse’s environment when considering time in the pasture?
stall the horses during peak feeding times
T/F: permethrin & oil products last longer than pyrethrins for insect control
true
what should be my first line of treatment for insect control?
topical insecticides, fly mesh, & fly sheets
what is atopic dermatitis?
genetically predisposed inflammatory & pruritic allergic skin disease with characteristic clinical features associated with IgE antibodies most commonly directed against environmental allergens - allergic to something in the environment
why should ‘buyer beware’ in cases of atopic dermatitis?
horse may have been sold in their good season when they are not clinical
can be seasonal or non-seasonal
how does an animal get atopic dermatitis?
inherited predisposition to form sensitizing antibodies to environmental allergens such as pollens, molds, dust, & storage mites
what are some examples of pro-inflammatory mediators in atopic dermatitis?
histamine, heparin, leukotrienes, prostaglandins, bradykinin, chymase, tryptase, & platelet activating factors
what is the lesion distribution of atopic dermatitis?
bilaterally symmetrical!! pruritus may or may not be generalized/seasonal
what clinical sign is commonly seen with atopic dermatitis?
urticaria
how is atopic dermatitis diagnosed?
clinical diagnosis is based on exclusion of other pruritic skin diseases - there is no specific test
but - positive serum/skin testing can support your diagnosis & guide therapy
what does treatment of atopic dermatitis with conservative medical management entail?
bathing, antihistamines, & fatty acid supplementation
what does treatment of atopic dermatitis with more aggressive medical management entail?
corticosteroids & apoquel - 0.25mg/kg
what does treatment of atopic dermatitis by retraining the immune system entail?
allergen specific immunotherapy
what are the downfalls of using steroids in horses?
possibility of developing laminitis, horses lack the ability of effective glucuronidation so use prednisolone instead of prednisone, & dexamethasone may have a lower probability of causing laminitis than other steroids
T/F: contact allergy in horses is rare
true
this lesion distribution in horses involves a type IV hypersensitivity & is rare in horses - what is it?
contact allergy
how do I avoid contact allergy in horses?
avoid the offending agents
what are the non-immunologic causes of urticaria?
cold-induced, exercise-induced, stress/psychogenic, sunlight, genetic, idiopathy, & dermatographism (pressure)
what are some examples of immunologic causes of urticaria?
allergic reaction, stinging insect, snake bite, infections, infestations, drug reactions (medication, vaccine, transfusion), plants, & vasculitis
what is the duration of chronic urticaria?
can last 6-8 weeks even though individual lesions are short lived - work up of the underlying cause/trigger is VERY important in these cases
T/F: with acute urticaria, empirical treatment with steroids/antihistamines can be used but you often won’t find the underlying cause/trigger
true
each individual lesion of urticaria can last as long as _______ hours even without treatment
24-48 hours
what does your history work-up for urticaria include? what else should be looked at?
previous medications, change in temperature, change in exercise, vaccinations, & season
animal’s environment
T/F: skin infections of horses are generally secondary to some other cause
true
what is an allergen?
antigen that favors the development of a hypersensitivity response
what is cellulitis?
diffuse inflammation of deep dermis & subcutaneous tissues
what is dermatophytosis?
fungal infection of keratinized skin, hair, or claws (ringworm)
what is furunculosis?
deep or penetrating folliculitis in which the integrity of the follicular wall has been compromised & follicular contents have escaped into the surrounding tissues
T/F: hyperpigmentation is often a result of chronic inflammation
true
what is leukoderma?
decreased pigmentation of the skin or non-pigmented skin
what is lichenification?
thickened/hardened skin with exaggerated epidermal markings seen in chronic skin disease
what is arguably the most important part of your dermatologic exam?
HISTORY
how do you diagnose lice?
combing - demonstrate nits/adult lice
what is the treatment for lice in warm weather? cold weather?
warm - bathing with insecticidal shampoo 3x a day for 10 days
colder weather/large number of animals affected - topical insecticides at labeled dose, typically 2 applications a day for 2 weeks
how do ticks causes problems in horses?
bite injury (secondary infection & myiasis), sucking blood, disease transmission, & tick paralysis
T/F: it is okay to use amitraz on horses with ticks
FALSE!!! don’t
how are psoroptes mites diagnosed? treatment?
skin scrape may or may not help - response to treatment is often helpful
topical & oral antiparasitics
like psoroptes, how is sarcoptes diagnosed? treated?
skin scrape may or may not help - response to treatment is often helpful
topical & oral antiparasitics
feathered breeds & draft breeds are most commonly affected by what mites?
chorioptes
how is chorioptes diagnosed? treatment?
skin scrape, combing/brushing of feathers, demonstration of mites
clip feathers, thorough cleaning of barn/disinfection of tools/tack, & topical antiparasitics
what would a biopsy look like in a positive animal for oncocerca cervicalis?
superficial & deep perivascular to interstitial dermatitis with numerous eosinophils & microfilariae usually in superficial dermis
how do you diagnose malassezia? treatment?
cytology - yeast adhered to keratinocytes, waxy/greasy areas yield best samples
focal areas - daily cleaning & spot application of antifungals
multifocal/generalized lesions - total body application of shampoo and/or rinse twice weekly for 3 weeks
what is the hallmark of clinical signs with insect bite hypersensitivity?
pruritus
T/F: serum allergy testing and/or intradermal testing for insect bite hypersensitivity does not diagnose allergy
true
