Common Skin Conditions in Horses Flashcards
What are some causes of pruritis in horses?
- Lice
- Mites
- Ticks
- Nematodes
- Hypersensitivity
Name 2 lice of horses
Werneckiella
Haematopinus asini
Describe the features of Werneckiella and where it affects horses
- Biting louse
- Feeds on epidermal debris
- Dorsolateral trunk, neck and face
- Common in the winter when horses have a thicker coat
Describe the features of Haematopinus asini and where it affects horses
- Sucking louse
- Feeds on blood
- Mane, tail, fetlock and pastern
How are lice treated and diagnosed?
Diagnosis using coat brushing and hair plucks
Treated with pyrethroids, fipronil, pyrethrins
Name some examples of mites found on horses
- Chorioptes equi
- Sarcoptes scabei
- Psoroptes equi
- Trombiculidiasis
Where on a horses body is affected by Chorioptes equi?
- Distal limbs where there are lots of feathers, particularly in draft breeds and cobs
- Warm, damp area
How will a horse show signs/react when they have a Chorioptes equi infection?
Intense pruritus with stamping/scratching/chewing of feet
What features of Chorioptes equi make the mite distinguishable?
- Cup shaped suckers on the ends of its limbs
- Dorsal anus
- Limbs extend past the body margins
Trombiculidiasis is also known as?
Harvest mites
Name the poultry mite which also affects horses?
Dermanyssus gallinae
How are mites diagnosed?
Skin brushings
How are mites treated?
- Macrocytic lactone injections
- Topical macrocytic lactones
- Topical shampoos: lime sulphur, selenium sulphate
Name the pinworm of horses
Oxyuris equi
Describe the features of Oxyuris equi and how that causes clinical signs
- Perianal pruritus
- Migrates out of the anus to lay eggs
- The glue they use to stick the eggs onto the skin causes itch
How is Oxyuris equi diagnosed?
Clinical signs + cellophane tape for diagnosis
- Lemon shaped eggs
How is Oxyuris equi treated?
Oral anthelmintics
Ulcerative nodules in spring and summer caused by fly larvae in the skin are due to which parasite?
Habronemiasis
Name the neck worm of horses
Onchocerca cervicalis
Where is Onchocerca cervicalis found in the horse?
- Adult lives in nuchal ligament
- Microfilarie migrate to skin → hypersensitivity
What is the cause of ‘sweet itch’
Culicoides spp
What are the features of Culicoides insect hypersensitivity
- Main, back, tail, ventrum
- Seasonal
- Reaction to the midges saliva
How is Culicoides insect hypersensitivity prevented?
- Avoid midge contact – move to a drier, windier location, cover with rug
- Reduce immune reaction e.g. steroids
What is atopy?
Sensitivity to multiple allergens
How is atopy diagnosed?
EXCLUSION (intradermal skin testing can help identify allergens)
How is atopy treated?
- Avoid allergen
- Immunotherapy
- Corticosteroids/ Antihistamines
- Improve Skin Barrier Function
Compare scaling vs crusting
Scaling: - Dry and grey Crusting: - Yellow, red, brown - Wet and damp with a serous ooze
Rain scald is caused by?
Dermatophilosis
Describe the characteristics and location of lesions due to Dermatophilosis
- Chronic moisture + skin damage activate bacteria
- Lesion: crust, moist mats of hair
- Back, rump, gluteal area, face, neck extremities
- Can be quite focal or extensive lesions
How is dermatophilosis diagnosed and treated?
Diagnosis: Cytology (smear pus onto a slide and look for the typical ‘train track’ appearance of the bacteria )
Treatment:
- Topical: mild cases
- Systemic antimicrobials: severe cases
Ring worm is also called?
Dermatophytosis
Which animals are susceptible to Dermatophytosis?
Young and immunocompromised
What are the signs of ringworm?
Circular patches of alopecia
How is ringworm diagnosed and treated?
- Diagnosis: fungal culture, PCR, microscopy
- Treatment: Topical antifungals (natamycin, enilconazole, miconazole)
What are the two causes of photosensitisation?
- Hepatogenous e.g. liver failure
- Ingestion or application of a photodynamic agent e.g. certain plant spp
Name 2 examples of plants that cause photosensitisation
- St johns wort
- Ragwort
Which plant leads to toxicity and irreversible liver failure?
Ragwort
Name the common disorder that affects non-pigmented areas on distal limb (lateral)
Leukocytoclastic vasculitis
How is Leukocytoclastic vasculitis treated?
- Avoid exposure to light
- Corticosteroids
- Wash legs to remove crusts
What is pemphigus foliaceous?
- Rare, autoimmune disease against desmosomes that hold cells together over the skin
- Causes severe crusting
Name the condition that causes grass warts
Viral papillomatosis
How is Viral papillomatosis treated?
- cosmetic issue
- don’t need to treat
What is the cause of warbles?
Larval stages of Hypoderma bovis and lineatum
How does warbles present?
Nodules with a central pore that is often painful
Describe the features of eosinophilic granuloma
- collagen necrosis
- single or multiple
- 0.5-10cm in size
- non-painful
- non-pruritic
What is seen on the histology of an eosinophilic granuloma complex?
Flame figures (collagen) and lots of inflammatory cells
What are the most common skin tumours of horses?
Sarcoids
Name the 6 clinical sarcoid presentation
- Occult
- Verrucose
- Nodular
- Fibroblastic
- Mixed
- Malignant
What is the danger with biopsying a sarcoid?
Dangers of exacerbating them and making them more aggressive
How are Sarcoids treated?
- Surgery / Laser Removal
- ‘Immune’ therapy - BCG Injections
- Cytotoxics (topical & injection)
- Antimitotics (topical)
- Photodynamic therapy
- Lots of treatment failures
What are the 4 prognosis rules for 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
Which tumour is common in grey horses?
Melanoma
Where are melanomas most commonly located?
Perineum
Tail
Head
Parotid region
Where are squamous cells carcinomas most commonly located?
- Most common in poorly pigmented animals
- Most common locations: external genitalia, eye
