Common skin conditions in horses Flashcards
What are common skin conditions in horses?
- Conditions that cause pruritus
- Conditions that cause crusting, scaling, erosion and/or ulceration
- Cutaneous swellings, nodules and tumours
What are the 2 causes of pruritus?
- Parasitic skin disease
- Hypersensitivities (allergies)
What are the parasitic causes?
- Lice (pediculosis) - most common
- Mites (mange)
- Ticks
- Nematodes
What are the 2 types of lice + where are they found?
- Werneckiella (previously Damalinia equi)
- Biting louse: feeds on epidermal debri
- Dorsolateral trunk, neck, and face
- Haematopinus asini
- Sucking louse: feeds on blood
- Mane and tail, fetlock and pastern
When are lice more common?
Winter - bigger coats
How are lice diagnosed?
*Coat brushes
*Hair plucks
How are lice treated?
pyrethrins
pyrethroids
permethrin
fipronil
*Treat originally + again 2 weeks later
What are the different mites that can cause pruritus?
- Dermanyssus gallinae
- Trombicula autumnalis
- Psoroptes equi
- Sarcoptes scabiei
- Chorioptes equi
Where is chorioptes seen?
- Distal limbs –lots of feathers (Draft
breeds and Cobs)
What does chorioptes equi cause?
- Intense pruritus with stamping/scratching/chewing of
feet
Where does sarcoptes affect? Why is it a concern?
*Affects entire body
*Problem as zoonotic
What parts of the body does Psoroptes equi affect?
- Forelock, main and tail
→ Trunk - Ears: headshaking
Where does trombicula affect? Why is it different?
*Different - larvae of free living mite = problem
* Face, distal limbs, ventral
thorax and abdomen
What is Dermanyssus gallinae? Where does it affect?
*Poultry mite
*Head + legs
How are mites diagnosed?
Skin brushings
How are mites treated?
*NO LICENSED PRODUCTS
– Inject macrocyclic lactones
* 2 injections, 2 weeks apart (SubCut)
– Topical macrocyclic lactones
* Once every 4 weeks
– Topical shampoos: lime sulphur shampoo, selenium sulphate shampoo, topical ivermectin
What nematodes can cause pruritus?
Oxyuris equi - pinworm
Where does the pinworm cause itching?
Perianal pruritus
What are different causes of hypersensitivities? (5)
- Insect hypersensitivity
- Food allergy
- Contact allergy
- Atopy
- Urticaria
What causes insect bite hypersensitivity?
*Culicoides spp
‘sweet itch’
Where does culicoides affect?
What are risk factors?
What is the treatment?
- Main, back, tail, ventrum
- Risks: standing water, dawn
and dusk - Treatment:
1. Avoid midge contact
2. Improve skin integrity
What does food allergy cause?
- Pruritus
± diarrhoea
± respiratory signs
How is atopy hypersensitivity diagnosed?
- Diagnosis: EXCLUSION
(intradermal skin testing can help
identify allergens)
How is atopy hypersensitivity treated?
- Treatment:
- Avoid allergen
- Immunotherapy
- Corticosteroids/Antihistamines
- Improve Skin Barrier Function
What does urticaria/hives hypersensitivity cause?
*Wheals
*Oedema
*Pruritus
How is urticaria / hives hypersensitivity treated?
*Corticosteroids
*Antihistamines
What is the difference between scaling + crust?
Scale = dry + grey - excess keratin
Crusting = yellow, red, brown - wet + damp
What is the difference between erosion+ ulceration?
Erosion = superficial
Ulceration = deeper
What can cause crusting, scaling, erosion or ulceration?
- Dermatophilosis (Rain Scald)
- Bacterial folliculitis
- Dermatophytosis (Ringworm)
- Photosensitization
- Leukocytoclastic vasculitis
- Pastern dermatitis
- Pemphigus foliaceous
What causes rain scald?
Dermatophilus congolensis
What area is affected by rain scald?
- Chronic moisture + skin damage
- Lesion: crust, moist mats of hair
- Back, gluteal area, face, neck extremities
How is rain scald diagnosed?
Cytology - smear pus on slide
How is rain scald treated?
- Topical: mild cases
- Systemic antimicrobials: severe cases
What causes bacterial folliculitis?
Staphylococcus (+streptococcus)
-Painful lesions
How is bacterial folliculitis diagnosed?
Cytology
Culture
What is the treatment of bacterial folliculitis?
- Topical: mild cases
- Systemic antimicrobials:
severe cases
What causes ringworm?
Trichophyton
Microsporum
What animals are affected by ringworm?
Young
Immunocompromised
What are the clinical signs of ringworm?
Circular patches of alopecia
How is ringworm diagnosed?
Fungal culture
PCR
microscopy
What is the treatment of ringworm?
Topical antifungals (natamycin, enilconazole, miconazole)
What are the 2 causes of photosensitization?
1.Hepatogenous - liver failure - ragwort
2. Ingestion / application of photodynamic agent - St. John’s wort
Where are lesions of photosensitization most common?
White areas
How is photosensitization diagnosed?
Signs
Blood tests
How is photosensitization treated?
*Treat liver disease
*Removal of agent
What parts of the body does leukocytoclastic vasculitis affect?
-non pigmented areas of distal limb (lateral)
-V PAINFUL
How is Leukocytoclastic vasculitis diagnosed?
Clinical signs
Skin biopsy
How is Leukocytoclastic vasculitis treated?
*Avoid exposure to light
*Corticosteroids
What can cause pastern dermatitis?
*Infectious agent
*Inflammatory
*Chronic disease
Where does pastern dermatitis affect?
Between hoof + fetlock
What is pemphigus foliaceous + what does it cause?
*Rare - autoimmune disease
*Causes severe crusting
How is pemphigus foliaceous diagnosed?
Skin biopsy
How is pemphigus foliaceous treated?
Immunosuppressive drugs
What can cause cutaneous swellings, nodules + tumours? (5)
- Viral Papillomatosis
- Warbles
- Genetic / developmental
- Eosinophilic granuloma
- Tumours
- Sarcoid
- Melanoma
- Squamous cell carcinoma
- Other: mast cell tumour, lymphoma
What are the causes of viral papillomatosis? How is it treated?
1.Grass warts - muzzle + face of young horses
2. Pinnal Acanthosis / aural placks
NO TREATMENT NEEDED
What are warbles?
Hypoderma bovis
HYpoderma lineatum
NOTIFIABLE
What is the treatment of warbles?
*Enlargement of pore to remove central grub
*Surgical removal
What are the genetic/ developmental causes of cutaneous swellings + nodules + tumours?
- Dentigerous cyst
- Atheroma
- Dermoid cyst
- Vascular hamartoma
What is an eosinophilic granuloma?
Collagen necrosis
-0.5-10cm
-non painful + non pruritic
How is an eosinophilic granuloma diagnosed + treated?
- Diagnosis: skin biopsy
- Treatment: surgical removal
What is the most common skin tumour in horses?
Sarcoid
What are sarcoids/ causes??
- Fibroblasts
- Bovine Papillomavirus 1 and 2
- Genetic predisposition
- Flies
What are the 6 clinical presentations of sarcoids?
*Occult sarcoid
*Verrucose sarcoid
*Nodular sarcoid
*Fibroblastic sarcoid
*Mixed sarcoid
*Malignant sarcoid
How is a sarcoid diagnosed?
Biopsy
How are sarcoids treated?
– Surgery / Laser Removal
– ‘Immune’ therapy = BCG Injections
– Cytotoxics (topical & injection)
– Antimitotics (AW4/5) (topical)
– Photodynamic therapy
– Brachytherapy = Iridium-wires (not available, but>90% successful)
What are the 4 rules of sarcoids?
– RULE 1:
The more they have the more they get
– RULE 2:
The fewer they have the fewer they get
– RULE 3:
Multiply over summer & grow over winter
– RULE 4:
A single sarcoid implies (genetic) susceptibility
How common are melanomas? Benign/malignant?
Where are they found?
*V common - (80% of grey horses >15y/o)
*Mostly benign
*Locations = perineum, tail head, parotid region
How is a melanoma diagnosed?
Clinical signs
Biopsy
How is a melanoma treated?
Surgical excision
Immunotherapy
What animals are squamous cell carcinoma most common in?
Poorly pigmented animals
What are the common locations of squamous cell carcinoma?
External genitalia
Eye
How is a squamous cell carcinoma diagnosed?
Clinical signs
Biopsy
What is the treatment of squamous cell carcinoma?
*surgical excision
*cryotherapy
*chemotherapy
What tumours are less common but found solitary on head + proximal limb and males are predisposed?
Mast cell tumours
When do melanomas tend to be more aggressive?
When not in a grey horse
