Equine dermatology Flashcards
What should you think of with older horses with derm disease?
- PPID
What should you think with Quarter Horses with skin disease?
- HERDA
History questions for equine dermatology
- Chronicity
- Initial distribution (where did it start?)
- Pruritic
- Treatments
Things to screen for during physical exam of horses with skin issues?
- Systemic diseases
- Nutritional imbalances
- Dermatological exam
Example history and PE of a horse with dermatophilosis
- 6 yo QH mare
- Winter
- Crusts and alopecia - clumps of hair like a paintbrush
- Very painful
- Starts on the dorsum
- Alopecic and non-pruritic
Dfdx for generalized exfoliation and crusts
- Dermatophilosis
- Dermatophytosis
- Contact dermatitis
- Bacterial infections (NOT COMMON)
- Immunologic
- Nutritional
Etiology of dermatophilosis
- Dermatophilus congolensis
Dermatophytosis etiology
- Trichophyton equinum or mentagrophytes
- Microsporum gypseum or canis
Which bacteria are most commonly responsible for bacterial infections?
- Staphylococcus
- Corynebacterium
- Streptococcus
Which immunologic diseases cause dermatologic conditions in the horse?
- Pemphigus foliaceus
- Equine eosinophilic dermatitis
- Stomatitis Sarcoidis
Which nutritional imbalances can lead to dermatologic conditions?
- Zn
- Iodine
- Protein
First step for a scaling/crusting disease?
What are you testing for?
- Saline mince prep of crust to test for dermatophilosis
- Stain with Diff quick
Second step for a scaling/crusting disease if the saline mince prep is negative?
- Fungal culture for dermatophytosis
Third step for a scaling/crusting disease if the saline mince prep and fungal culture are both negative?
- Biopsy and histopathology
- Testing for pemphigus foliaceus, bacterial folliculitis, granulomatous disease, others
What if all the ttests are negative?
- Recheck diagnosis and repeat tests
Locations of lesions in dermatophilosis
- Black, gluteal area, face, neck
Lesions with dermatophilosis
- Crusted, moist mats
- Paintbrushes
- Under the crust is a yellowish exudate
- Painful
Other clinical signs seen with dermatophilosis
- Fever
- Lethargy
- Anorexia
DIagnosis of dermatophilosis
- Crust mince
- Diff quick or gram stain: Gram positive
- Railroad tracks
Treatment for dermatophilosis
- Soak and remove crusts (PAINFUL)
- May need NSAIDs
- If severe cases, use antibiotics
What type of scrub do you use to remove dermatophilus crusts?
- Chlorhexidine scrub (2%)
- Benzoyl peroxide shampoo
- Once a day for a week
- 2 weeks until resolution
Case history and signs with an allergic reaction?
- Shortly after arrival had a “reaction”
- Not pruritic
- Not painful to palpation
- Urticaria
Urticaria clinical signs
Pruritic?
- Wheals and edema
- Variable pruritus
Antigens for urticaria
- Hard to identify
Treatment for urticaria
- Hard to identify
- Remove the cause if possible for 2-3 days
- corticosteroids
- Antihistamines (don’t help much)
How long can it take for urticaria to go away?
- It can take 2-3 days
Typical signalment and history for hereditary equine regional dermal asthenia (HERDA)
- 3 year old QH gelding
- Healthy
- Cutting
- Beginning work under the saddle
- Moderate to severe skin lacerations
WHo gets hereditary equine regional dermal asthenia?
- Quarter Horses from Cutting lines
Inheritance pattern for hereditary equine regional dermal asthenia?
- Autosomal recessives
- Both parents must be carriers
Testing for hereditary equine regional dermal asthenia?
Sample type?
- Genetic tests available
- Carrier vs affected
- Hair with roots
What is the underlying disease with hereditary equine regional dermal asthenia?
- Collagen defect (hyperextensible skin mostly on the dorsum)
When does hereditary equine regional dermal asthenia usually become apparent?
- Often when they go to saddle the horse
Diagnosis of hereditary equine regional dermal asthenia?
- Clinical signs
- Breed (QH)
- Biopsy
- DNA
Treatment for hereditary equine regional dermal asthenia?
- Nothing
- Often have to be put down
What are the four big categories for pruritic dermatoses
- Parasites
- Allergies
- Bacterial folliculitis
- Fungal infections
WHat is the most common cause of pruritic dermatosis in horses?
- Insect bite hypersensitivity
Parasites that can affect horses
- Lice
- Mites (draft horses)
- Ticks (uncommon here)
- Onchocerca
- Habronema
- Pinworms
When do most horses tend to get pinworms?
- During pregnancy
Insect-bite hypersensitivity time course
- Chronic and recurrent
- Often seasonal
Most common etiology of insect bite hypersensitivity
- Culicoides
What type of hypersensitivity is associated with Culicoides?
- Cell type involved and cytokine involved?
- Types I and IV hypersensitivity
- Eosinophils
- IL-5
Complications of insect-bite hypersensitivity
- Secondary infections
Diagnosis of insect bite hypersensitivity
- Serology not useful
- Intardermal testing has false positives
- CLinical signs and seasonality
- Response to management
Management for IBH
- Stable mid afternoon to mid-morning
- Screens and fans
- Fly sheets and fly masks
- Environment (fly predators, traps, sanitation)
- Long acting repellents (don’t work for her)
- Sheet blankets + repellent
- Zebra coats may help
What topicals for IBH?
- 2% permethrin
- Cypermethrin
Medications to decrease pruritus in horses?
- Corticosteroids
- Shampoo
- Omega-3 fatty acids
- Antihistamines not effective
Anti-IL5 vaccine for IBH prevention
- Not in the US yet
- 47% horses improved their clinical signs by 50%
- 13% of non-vaccinated horses improved
- Costs a lot of money
What should you think in a horse with dermatoses in the white portion of the skin only?
- Think sunburn
- But also think liver disease!
