Equine Dermatology Flashcards
What are the common dermatological diseases of horses?
- Pediculosis: louse infestation
- Chorioptes
- Insect hypersensitivity: Sweet itch
- Dematophilosis: Rain scald
- Dermatophytosis: Ringworm
- Pastern Dermatitis
- Urticaria: hives
- Equine Coital Exanthema
- Sarcoids: Bovine papillomavirus
- Melanomas
- Squamous Cell Carcinoma
- Miscellaneous Conditions: Autoimmune diseases (Pemphigus)
Where on the horse are lice infestations (pediculosis) more commonly seen?
- Neck, dorsum, maine and tail
But they can occur anywhere on the body
How can you treat/ control Pediculosis in horses?
- Fipronil, permethrin
- Sucking lice (H. asini) can be treated with oral Ivermectin, 2 doses separated by 14 days
- Wash/ clean everything!
note: no pour-ons licensed for use in horses
What are the 2 species of Horse lice?
- Haematopinus asini (sucking lice)
- Damalinia equi (biting)
Where on the horse is the Chorioptes mite usually found?
- Around the feathers of the legs, you will see the horses stamping and scratching their legs
How can you treat Chorioptes mites in horses?
- Fipronil, permethrin
- Oral Ivermectin, 2 doses separated by 14 days
- Wash/ clean everything!
What is the offending ectoparasite that causes Sweet Itch in horses?
Cullicoides midges (usually) - The horse elicits a hypersensitivity reaction to the salivary proteins of the midge
Where on the horse is Sweet Itch skin lesions usually seen?
Face, ears, mane, tail head, ventral midline
How can Sweet Itch be treated/ prevented in horses?
- Anti-inflammatories: usually steroids BUT keep in mind the risk of laminitis
- Anti-itching shampoos
- Increase omega 6 + 3 fatty acids
- Insecticide spray used at dawn and dusk when the midges are most active
- Stabling at dawn and dusk
- Insect rugs
What is the cause of Rain Scald/ Mud Rash in horses?
- Infection of the skin caused by chronic moisture + skin damage
- Etiological agent: Dermatophilus congolensis
How can you treat Rain Scald/ Mud Rash/ Dermatophilosis in horses?
- Gently remove crusts/ scabs/ lesions with moist hibiscrub gauze
- Antibacterial shampoo or cream
- Then keep the animal dry
note: rarely need systemic Ab’s
How can Ringworm be treated in horses?
- This is a self-limiting infection and will go away over 6-12 weeks
- Tx: Imaverol Fungacidal wash
What is Pastern Dermatitis/ Greasy heel/ Mud Fever, in horses?
A condition characterized by bilateral inflammation, crusting, and exudate of the caudal aspect of the pattern region, with multiple etiologies involved
What is the cause of Pastern Dermatitis/ Greasy heel/ Mud Fever, in horses?
Multiple etiologies:
- Bacterial: Staph spp, Dermatophilus
- Parasitic: Chorioptes, Trobiculidae
- Environmental: irritants
- Immunological: Pemphigus, vasculitis, hypersensitivity
What is the treatment for Pastern Dermatitis/ Greasy heel/ Mud Fever, in horses?
1) Clip the area
2) Soak in antiseptics
3) Steroids topically: decrease proliferation of tissue
4) Surgical excision of exuberant tissue
What is the cause of Urticaria (hives) in horses?
- A Hypersensitivity reaction to almost anything, can be a drug, feed, washing powder, brush etc.
What is the treatment for Urticaria (hives) in horses?
1) Steroids if absolutely necessary: oral prednisolone is safer than Dexamethasone
2) Avoid the cause of the hypersensitivity: remove drug, shampoos, insects, diet
3) Hydroxyzine: anti-histamine. Limited value
4) Adrenaline: only used in severe cases where the risk of angioedema is possible
What disease does Equine Herpesvirus 3 cause?
Equine coital exanthema
- Circular vesicles, pustules, and ulcers form around the genitals of both sexes (sexually transmitted)
+/- purulent discharge from secondary bacterial infection
How can Equine Herpesvirus 3 be diagnosed?
- Clinical signs/ lesions are very obvious
- PCR for definitive
How can Equine Herpesvirus 3 be treated?
- Supportive care
- Good hygiene practices
- Rest
- Antimicrobials for secondary bacterial infections
- Ointment of antiviral ancyclovir
What virus causes Equine Sarcoids?
Bovine Papillomavirus
Where on the horse can sarcoids develop?
Anywhere on the body, with a predilection for the head, axilla, and groin
Locally invasive but not metastasis
How can Equine Sarcoids be treated?
- No treatment, just monitor: sometimes best not to aggravate it
- Surgical removal/ debulking (varying efficacy) +/- laser therapy or cryotherapy
What is the range of presentation of Equine Sarcoids?
- Occult: looks like ringworm
- Verrucose: warty-like presentation
- Nodular: Type A is SQ. Type B involves the skin and the skin cant be moved over the nodule
- Fibroblastic: fleshy appearance. Type 1 is pedunculated. Type 2 has a brad base and is locally invasive
- Malignant: Aggressive, locally invasive and can extend widely
- Mixed: the majority of horses have multiple versions of sarcoids
Are melanomas usually benign or metastatic in horses?
Usually benign and slow-growing, but can become problematic depending on their location
Can become malignant and can metastasize though
What are the treatment options for melanomas in horses?
- Surgery
- Cryosurgery
- Injection with Cisplatin
- Medical treatment with Cimetidine: may prevent growth of the tumors, but doesn’t cause regression of the tumor
Where on the horse is squamous cell carcinomas usually seen?
Non-pigmented areas of the face or on the penis
What is the rate of metastasis of squamous cell carcinoma in horses?
~20%
Usually travels to the draining lymph nodes
What is the treatment options for Squamous cell carcinoma in horses?
- Surgical removal
- Cryosurgery
- Radiation therapy
You notice a horse has a tumor-like mass close to its eye, what are the potential tumors that can grow here?
- Squamous Cell Carcinoma
- Melanoma
- Sarcoids
What is the cause of Pemphigus foliaceus?
An Autoimmune disease, where antibodies are produced against the epidermal cell membranes
What is the common presentation of Pemphigus foliaceus in horses?
- Exfoliative dermatitis
- Flaky, crusts, vesicles
- Coronary band inflammation
- Alopecia
- Painful pruritis in 1/3 of cases
How can Pemphigus foliaceus be diagnosed?
- Biopsy: looking for epidermal separation and blistering
- Direct immuno-fluorescence to pick up the antibodies
How can Pemphigus foliaceus be treated in horses, and what is the prognosis?
Tx: Prednisolone
Prognosis: Good in young horses that can grow out of it, Guarded in older horses who will likely be on prednisolone for the rest of their life
What is the difference between Pemphigus foliceus, Pemphigus vulgaris and Pemphigoid?
All are autoimmune diseases, differences lie in their location, severity and prognosis
- Pemphigus foliaceus causes exfoliative dermatitis. It’s milder than pemphigus vulgaris.
- Pemphigus vulgaris affects not just the skin, but also the mucous membranes. It causes painful blisters to form on the mucous membranes
- Pemphigoid affects a lower layer of the skin, between the epidermis and the dermis, creating tense blisters that do not break easily. Sometimes pemphigoid may look like hives without blisters.
