Exam #3: Equine Derm Flashcards
(57 cards)
Six main categories of equine derm problems
1) Pruritus
2) Crusting and scaling
3) Ulcers and erosions
4) Lumps and bumps
5) Discoloration
6) Hair coat changes
Main diagnostics tests for equine derm conditions (8)
- Similar to small animal derm
1) Skin scrape
2) Combings of mane, tail, feathers (ectoparasites)
3) Scotch tape preps (cytology)
4) Trichograms
5) Dermatophyte culture- monitor freq so it’s not overgrown by normal bacteria of saprophytic fungi
6) Impression smear or crust cytology
7) Culture for bacterial or fungus
8) Skin biopsy - Suspect systemic dz? run CBC, chem, diet elimination trials, intradermal testing
Top four differentials for pruritus in horses
1) Ectoparasites
2) Insect hypersensitivity
3) Allergic hypersensitivity
4) Urticaria
DDx? Pruritus of lower legs, tail, foot, (may become generalized), “scratches”, alopecia, crust formation
> Mites
- Most commonly in horses is Chorioptes (legs, tail, foot)
- Psoroptes (droopy ears, mane, trunk involvement)
Treatment of choice for mites
Ivermectin, others = 5% lime sulfur
Dx? Intense pruritus, beginning on the head, non-follicular papules, crusts, excoriations, alopecia
Mites = Sarcoptes
- Cross-species transmission possible
- Reportable and zoonotic
What time of year are parasitic skin pathologies more common?
Winter = often more severe then
Dx? Pruritus, restlessness, poor hair coat quality, alopecia, excessive grooming of mane, head, tail, fetlocks (affected animals may be asymptomatic and just “twitchy”)
> Lice (pediculosis)
- Common in young or old/debilitated animals
- Overcrowding predisposes
- Common in colder months
Common anatomic locations of biting and sucking lice
- Biting louse (Damalina) = dorsolateral trunk, mobile
- Sucking louse (Haematopinus) = mane, tail, fetlock, stationary
Difference in location on horse between Chorioptes and Psoroptes
1) Chorioptes = leg, tail, foot
2) Psoroptes = ears, mane, tail
Treatment of lice
- Treat all animals in contact = ivermectin
- Clean environment
Dx? Pruritus, papules, wheals on muzzle and distal limbs
Chiggers (common in late summer/fall)
Dx? Anal pruritus, tail rubbing and alopecia
Pinworms - Oxyuris equi
DDX: tail pyoderma, insect bite hypersensitivity, atopic dermatitis, food allergy, chorioptic/psoroptic mange
True or false - pinworms are species specific?
True
Dx? Pruritus, painful papules and wheals with a central crust
> Biting flies
- Tabanids = horse flies = ventrum, legs, neck, withers (individual strikes/bites)
- Stomoxys = stable flies = neck, back, groin, chest, legs
Dx? Ventral midline dermatitis
Horn fly bites
What is the most common allergic skin disease in horses?
Insect bite hypersensitivity
Dx? Pruritus (location varies, common face, mane, tail, ventrum, dorsum), papules, wheals, crusts, secondary alopecia, self trauma (etc.)
Hypersensitivity to Culicoides fly saliva
Treatment of insect bite hypersensitivity
1) Limit insect exposure
2) Environmental control
3) Anti-histamines
4) Topical and systemic steroids
+/- Immunotherapy (conflicting evidence)
Dx? Chronic urticaria, generalized pruritus, secondary excoriations, lichenification, alopecia
Atopic dermatitis to environmental antigens
Diagnosis and treatment of atopic dermatitis
- Dx: exclusion
- Tx: symptomatic (corticosteroids, anti-histamines), immunotherapy
Which is more common with pruritus in horses: food allergy or contact reactions?
- More common = contact reactions, Ex: tack, saddle, irritants.
- Rare = food allergy
How do we view urticaria in horses?
> REACTION PATTERNS from different etiologies or pathogeneses (angioedema)
+ Wheal (flat topped with steep walled sides)
*Should “pit” with pressure
DDx for urticaria (6)
1) Hypersensitivity reactions
2) Drug rxns
3) Physical = cold temp, exercise induced, dermatographism
4) Stress
5) Vasculitis
6) Arthropods
