Skin conditions of the horse Flashcards
Differentials for pruritic skin disease.
Parasitic skin disease
Hypersensitivity
Name a sucking louse which feeds on the horses blood and can be found in the mane, tail, fetlocks and pastern
Haematopinus ascini
This biting louse is more common in young animals and is found on the dorsolateral trunk.
Weneckiela equi (aka damalinia)
Malophagia
Feeds on epidermal debri
How can lice be transmitted between horses?
Direct contact
Indirect contact - brushes, tack, rugs etc
What clinical signs are associated with a louse infection in the horse?
+/- Asymptomatic
Restless
Poor appetite
+/- Pruritis
Poor coat - dull, alopecia
Severe debilitation
Treatment: Synthetic pyrethroids
This mite species causes intense pruritis and is mostly found in the distal limbs of feathered horses.
Outline the morphological features
Chorioptes equi
Cup-shaped sucker on a segmented pedicle
This zoonotic mite is mostly found on the head, neck and ears (but can be the whole body) and is notably difficult to find on skin scrapings.
Sarcoptes scabei
This host-specific mite is a cause of head-shaking in the horse.
Morphologically you will find trumpet shaped suckers on the jointed pedicle.
Psoroptes equi
What sampling technique should be employed for finding mites?
Skin brushing
Outline several treatment protocol and control policies for getting rid of mites.
Treatment: Avermectins (not-liscenced), lime sulphur, diazinon etc
Control: clip feathers, dinifect all rugs, tack, stable
This free living adult mite lays eggs on the horse leading to papules containing small orange larvae on ventral areas of the body.
Trombicularis
This mite species is a poultry mite which can be transmitted to horses and causes severe pruritis.
Dermanyssus gallinae
This commensal mite often causes pathology if the patient is immunosuppressed.
Which species are involved and where are they found?
Demodex:
Equi: body
Caballi: eyelids and muzzle
AKA neck threadworm
Onchocerca cervicalis
How does the neck threadworm cause pruritis in the horse?
Microfilarie migrate from the nuchual ligament to the skin and cause hypersensitivity.
(Can also cause ocular lesions)
This nematode is transmitted by flies which deposit larvae around wounds.
What clinical lesions are seen?
Habronema
Lesions: ulcerative nodules which show exuberant growth of granulation tissue with yellow granules.
Pinworm
How does this nematode cause pathology?
Oxyuris equi
Female saliva causes perianal hypersensitivity
Seasonal recurrent dermatitis.
Spread by which fly species?
Sweet itch
Culicoides
With diet elimination therapy how long should the protocol last?
- 4-6 weeks on the basic diet (hay/grass)
- Reintroduce further foods
How can contact allergy by diagnosed or controlled?
Dx. Provocative exposure
Tx. Avoid contact
Type one hypersensitivity causing wheals, oedema and often pruritis/ discomfort.
Urticaria (aka hives)
Tx. steroids/ anti-histamines
What is the difference between scaling and crusting?
Scale is dry and grey
Crusting is yellow-red and is wet/ damp
Differentials for crusting, scaling, erosions and ulcerations.
- Viral papillomatosis
- Dermatophilosis
- Bacterial folliculitis
- Dermatophytosis
- Photosensitive
- Leukoclastic vasculitis
- Pastern dermatitis
- Pemphigus folliaceous
Viral papillomatosis is characterosed by what?
Pineal acanthosis
Aural plaques
Grass warts
Rain scald is caused by what bacteria?
What clinical signs are associated?
Dermatophilus congolensis
- Crusts
- Moist mats of hair
- Found on back, gluteals and face
What bacteria is depicted here?
Dermatophilosis tracks of bacteria
Which bacterial folliculitis is more painful? Staphs or streps?
Staphs
Ring worm
AKA
Which species are the cause?
What clinical signs are associated with the species?
Dermatophytosis
spp. Trichophyton and Microsporium
C/S: Cigarette ash circular patched of fragile hair
Differentials for photosensitisation
Hapatogenous
Ingestion/ application of photodynamic agents
What histological features are associated with leukoclastic vasculitis?
Perivascular cuffing of leukocytes
Vasculitis (hypersensitivity T3)
Affects only non-pigmented skin
Mud fever
What sequelae are associated?
Pastern dermatitis
Chronic hyperplastic haemorrhagic dermatitis.
What clinical signs are associated with pemphigous folliaceous?
What pathogenesis causes this?
Severe crusting
Autoimmunity against demoglein 1 (superficial skin) causing blistering/ sloughing of epidermis.
Warbles are caused by what species?
Hypoderma bovis/ lineatum
REPORTABLE
Dentigerous cyst
Nodular growth of dental tissue
Atheroma
Fatty lumps within arterial walls leading to nodular skin swelling
Dermoid cyst
Teratoma containing epithelium, hair follicles and sebaceous glands
Vascular harmatoma
Abnormal blood vessels which develop in utero
Eosinophilic granuloma
Collagen necrosis
Sarcoid
Definition and potential aetiologies
A fibroblastic skin tumour
Causes: genetic predisposition, bovine papilloma 1 and 2
Name the six different presentations of sarcoid
- Occult - ring, vessel associated
- Verrucose - warty
- Nodular - lump
- Fibroblastic - fleshy
- Mixed
- Malignant - very aggressive
What is the gold standard treatment option for sarcoid treatment?
Radiation therapy
This tumour type is mostly found in greay old horses around the perineum, tail head and parotid region.
Melanoma
This tumour type is mostly found in poorly pigmented animals (UV damage) and usually associated with external genitalia and eye (third eyelid)
Squamous cell carcinoma
