Equine Dermatology Flashcards

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1
Q

What are the common dermatological diseases of horses?

A
  • 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)
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2
Q

Where on the horse are lice infestations (pediculosis) more commonly seen?

A
  • Neck, dorsum, maine and tail

But they can occur anywhere on the body

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3
Q

How can you treat/ control Pediculosis in horses?

A
  • 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

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4
Q

What are the 2 species of Horse lice?

A
  • Haematopinus asini (sucking lice)

- Damalinia equi (biting)

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5
Q

Where on the horse is the Chorioptes mite usually found?

A
  • Around the feathers of the legs, you will see the horses stamping and scratching their legs
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6
Q

How can you treat Chorioptes mites in horses?

A
  • Fipronil, permethrin
  • Oral Ivermectin, 2 doses separated by 14 days
  • Wash/ clean everything!
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7
Q

What is the offending ectoparasite that causes Sweet Itch in horses?

A
Cullicoides midges (usually)
- The horse elicits a hypersensitivity reaction to the salivary proteins of the midge
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8
Q

Where on the horse is Sweet Itch skin lesions usually seen?

A

Face, ears, mane, tail head, ventral midline

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9
Q

How can Sweet Itch be treated/ prevented in horses?

A
  • 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
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10
Q

What is the cause of Rain Scald/ Mud Rash in horses?

A
  • Infection of the skin caused by chronic moisture + skin damage
  • Etiological agent: Dermatophilus congolensis
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11
Q

How can you treat Rain Scald/ Mud Rash/ Dermatophilosis in horses?

A
  • Gently remove crusts/ scabs/ lesions with moist hibiscrub gauze
  • Antibacterial shampoo or cream
  • Then keep the animal dry

note: rarely need systemic Ab’s

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12
Q

How can Ringworm be treated in horses?

A
  • This is a self-limiting infection and will go away over 6-12 weeks
  • Tx: Imaverol Fungacidal wash
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13
Q

What is Pastern Dermatitis/ Greasy heel/ Mud Fever, in horses?

A

A condition characterized by bilateral inflammation, crusting, and exudate of the caudal aspect of the pattern region, with multiple etiologies involved

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14
Q

What is the cause of Pastern Dermatitis/ Greasy heel/ Mud Fever, in horses?

A

Multiple etiologies:

  • Bacterial: Staph spp, Dermatophilus
  • Parasitic: Chorioptes, Trobiculidae
  • Environmental: irritants
  • Immunological: Pemphigus, vasculitis, hypersensitivity
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15
Q

What is the treatment for Pastern Dermatitis/ Greasy heel/ Mud Fever, in horses?

A

1) Clip the area
2) Soak in antiseptics
3) Steroids topically: decrease proliferation of tissue
4) Surgical excision of exuberant tissue

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16
Q

What is the cause of Urticaria (hives) in horses?

A
  • A Hypersensitivity reaction to almost anything, can be a drug, feed, washing powder, brush etc.
17
Q

What is the treatment for Urticaria (hives) in horses?

A

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

18
Q

What disease does Equine Herpesvirus 3 cause?

A

Equine coital exanthema
- Circular vesicles, pustules, and ulcers form around the genitals of both sexes (sexually transmitted)
+/- purulent discharge from secondary bacterial infection

19
Q

How can Equine Herpesvirus 3 be diagnosed?

A
  • Clinical signs/ lesions are very obvious

- PCR for definitive

20
Q

How can Equine Herpesvirus 3 be treated?

A
  • Supportive care
  • Good hygiene practices
  • Rest
  • Antimicrobials for secondary bacterial infections
  • Ointment of antiviral ancyclovir
21
Q

What virus causes Equine Sarcoids?

A

Bovine Papillomavirus

22
Q

Where on the horse can sarcoids develop?

A

Anywhere on the body, with a predilection for the head, axilla, and groin
Locally invasive but not metastasis

23
Q

How can Equine Sarcoids be treated?

A
  • No treatment, just monitor: sometimes best not to aggravate it
  • Surgical removal/ debulking (varying efficacy) +/- laser therapy or cryotherapy
24
Q

What is the range of presentation of Equine Sarcoids?

A
  • 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
25
Q

Are melanomas usually benign or metastatic in horses?

A

Usually benign and slow-growing, but can become problematic depending on their location

Can become malignant and can metastasize though

26
Q

What are the treatment options for melanomas in horses?

A
  • Surgery
  • Cryosurgery
  • Injection with Cisplatin
  • Medical treatment with Cimetidine: may prevent growth of the tumors, but doesn’t cause regression of the tumor
27
Q

Where on the horse is squamous cell carcinomas usually seen?

A

Non-pigmented areas of the face or on the penis

28
Q

What is the rate of metastasis of squamous cell carcinoma in horses?

A

~20%

Usually travels to the draining lymph nodes

29
Q

What is the treatment options for Squamous cell carcinoma in horses?

A
  • Surgical removal
  • Cryosurgery
  • Radiation therapy
30
Q

You notice a horse has a tumor-like mass close to its eye, what are the potential tumors that can grow here?

A
  • Squamous Cell Carcinoma
  • Melanoma
  • Sarcoids
31
Q

What is the cause of Pemphigus foliaceus?

A

An Autoimmune disease, where antibodies are produced against the epidermal cell membranes

32
Q

What is the common presentation of Pemphigus foliaceus in horses?

A
  • Exfoliative dermatitis
  • Flaky, crusts, vesicles
  • Coronary band inflammation
  • Alopecia
  • Painful pruritis in 1/3 of cases
33
Q

How can Pemphigus foliaceus be diagnosed?

A
  • Biopsy: looking for epidermal separation and blistering

- Direct immuno-fluorescence to pick up the antibodies

34
Q

How can Pemphigus foliaceus be treated in horses, and what is the prognosis?

A

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

35
Q

What is the difference between Pemphigus foliceus, Pemphigus vulgaris and Pemphigoid?

A

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.