8. Equine Dermatology

What are the TWO most common causes of equine dermatitis?

Atopy

insect hypersensitivity

What is the etiology and pathogenesis of atopy in horses?

puritic disease that the horses are sensitized if there are high levels of IgE

What are the TWO things that the history can tell you?

-seasonal

-non seasonal

Where is the distribution of lesions in a horse with atopy?

- faces

- ears

- ventrum

- legs

-tail

- +/- mane

How would you describe how you diagnose atopy?

diagnosis of exclusion

What is the gold standard diagnostic test for equine atopy?

IDAT

What diagnostic is not recommended in horses for atopy?

serum

What are TWO ddx for atopy?

- insect hypersensitivity

- food allergy

What are the FOUR things that you can use to treat Atopy in horses?

Hyposensitization

• Prednisolone

• Dexamethasone

• Hydroxyzine

What are the types of hypersenivities that food allergy can cause?

Type I, III, IV

T/F Food allergy in horses is uncommon

True

What would be a sign in the history that would help you to determine that the allergy is a food allergy?

non-seasonal

Where is the sign of pruritus in food allergy manifest?

• Tail

• Mane

• Face

How do you diagnose food allergy?

elimination diet with grass only

If you give steroids and the issues do not resolve, what should your top ddx be?

food allergy

What are TWO ddx for food allergy in horse?

- atopy

- ectoparasite

What are the TWO treatments for food allergy?

- avoidance

- glucocorticoids

What is always the top DDX if the season is right when it comes to equine dermatology?

Culicoides Hypersensitivity

What type of reactions does Culicoides cause?

Type 1 and Type 4

When are Culicoides most active and when is the seasonality?

active: morning and evening

season: warm flyers

What is super important to know about Culicoides because it can help you to eliminate them?

they are weak flyers

Where is the MOST common area of intense pruritus seen with Culicoides hypersensitivity? ( this is in red)

Maine and Tail

Where else can Culicoides lesions be?

dorsal, ventral, both

How do you diagnose Culicoides hypersensitivity?

- history and finding

- IDAT

What is the limitation to using IDAT?

It can only pick up the type 1 hypersensitivity ( IgE)

T/F A biopsy would be helpful to perform with Culicoides hypersensitivity because you will be able to see the larvae

False, you dont see sh*t

What are the top DDX for Culicoides hypersensitivity?

- atopy

- ecotoparasites

What is the treatment for Culicoides? (it says know this so i would recommend that)

- Permethrin (late afternoon repellant)

- Fine mesh screen

- FANS (them hoes are weak)

- Remove standing water

T/F Some people use off label ear tags to help with Culicoides

True

What are the drugs that you can use to treat Culicoides hypersensitivity?

- prednisolone

- hyroxyzine

- Dexamethasone

T/F You want to get the horse on the lowest dose of steroids possible when treating for allergies

true

What are the FOUR things that you should inform the owner about with Culicoides hypersensitivity?

- there is no cure

- fly control is important

- Steroid abuse

- Move north

What makes Culicoides and Blackfly different in terms of etiology?

blackfly needs moving water to breed

When are blackflys most active?

- evening and morning

- spring and summer

T/F Like Culicoides, Blackflys are weak flyers

False, they are strong flyers

What are the clinical findings of Blackfly hypersensitivity?

- pain

- pruritus

Where is the distribution of Blackfly hypersensitivity?

- ear

- intermandibular

- ventral

- inner legs

How do you diagnose Blackfly hypersensitivity?

-clinical signs

- history

What is the DDX for Blackfly hypersensitivity?

-atopy

- ectoparasites

What is the treatment for Blackfly dermatitis?

- morning and late afternoon spray

- prednisolone

What do stable flies require for breeding?

fresh feces

When are Stable flys most active seasonally?

summer and fall

What are the clinical signs for Stable fly dermatitis?

- hypersensitivity

- pain

- urticaria

What is the distribution of stable fly dermatitis?

ventral and all over

How can you help to control the amount of stable flies present?

fly control: manure removal, fly traps

What disease is a type 1 reaction and see with immune reactions, allergies, and non immune causes, cold/ exercise and 50% of cases are idiopathic?

Urticaria

What are some causes of urticaria? (there is alot)

-drugs

- allergy (insect, atopy, food)

- trauma

- cold

- heat

- exercise

- topical meds

What is the pathogenesis of urticaria?

- mast cell degranulation that causes histamine release and causes an influx of proimflammatory mediators

How do you diagnose urticaria?

-clinical finding

- biopsy

What is the treatment for urticaria?

- find the cause

- hydroxyzine

- prednisolone

Where will you find Onchocerca cervicalis? (i have hella stars by this)

adult worms inhabit ligamentum nuchae

What life cycle stage of Onchocerca causes the skin lesion?

microfilaria

What is the intermediate host for Onchocerca?

Culicoides

T/F Equine cutaneous onchocerciasis is caused by a hypersensitivty to the eggs and they have ocular involvement.

False it is the microfilaria

Why do we not have alot of issues with Equine cutaneous onchocerciasis?

ivermectin

Equine cutaneous onchocerciasis is usually seen in what age horses

> 4 years old

What are the clinical signs of Equine cutaneous onchocerciasis?

- worse in the summer

- focal annular alopecia w scale

How do you diagnose Equine cutaneous onchocerciasis? (also have hella stars by this?

minced tissue to identify microfilaria

What is the treatment for Equine cutaneous onchocerciasis?

ivermectin

What adult worm lives in the stomach and has the eggs and larvae passed in the feces and the reaction causes hypersensitivity?

Habronemiasis (summer sores)

What is a clinical sign of Habronemiasis?

- exuberant granulation tissue

- ulcerated nodules

- draining tracts

Where do the Habronemiasis lesion resign?

- medial canthis

- prepuce

- uretheral process

- lower limbs

T/F When diagnosing Habronemiasis, you should treat for it first then follow up with the other DDX

True

What are the DDX for Habronemiasis?

- pythium

- sarcoid

- SCC

- Proud flesh

What is the treatment for Habronemiasis?

- ivermectin

- Pred

- Fly control