Equine dermatology Flashcards
What are tap strips useful for identifying
Lice, oxyurid eggs
(may use for mites but they are often deeper)
What do we need to remember to do in weeks before taking a skin biopsy
Discontinue any anti-inflammatories as they can affect. the histopathology of the lesions
How might we take a different approach with biopsying the coronary band
Use a shave biopsy rather than full skin thickness to avoid changing the hoof growth
Or could sample from other spots e.g chestnuts often similarly affected
Two types of lice that are important in horses
Damalinia equi = biting louse
Haematopinus asini = sucking louse
Treatment of lice in horses
Permethrin or cypermethrin twice, two weeks apart
Which mite species that affect horses are zoonotic
Sarcoptic scabei
Tombicula (= chiggers/harvest mite)
Which mite typically affects the legs esp in feathered breeds
Chorioptes equi
= ‘feather mite’
Mite lesions on body is suggestive of which mite species
Psoroptes equi
Mite lesions on head is suggestive of which mite species
Sarcoptes scabei
Treatment of chorioptes
mites
CLipping feathers before doing topical fipronil spray
Injectable doramectin subcut twice, 2 weeks apart
Selenium shampoo washing
Mite lesions on legs/face/muzzle/ventral abdomen is indicative of which species
Trombicula
What is oxyuris equi and what are the signs and treatment
Pinworm
Gravid females in the GI tract stick eggs to the perineal skin causing itching, tail rubbing and self-trauma of rump
Treat with ivermectin/moxidection (if resistant to this go for pyrantel/fenbendazole)
What are ‘summer sores’
Nodular, ulcerated skin lesions around muco-cutaenous junctions caused by Habronema L3 larvae
How can we diagnose habronemiasis
Can do impression smear to look for L3 s
Gold standard is histopath; often taken to differentiate from sarcoids (a tumour)
What is onchocerciasis
Itchy skin due to onchocerca cervicalis microfilaria
= vector born nematode spread by culicoides
Life cycle of onchocerca cervicalis
Adults live in nuchal ligament and produce microfilaria
Microfilaria migrate to the skin
Get ingested by culicoides midges and transform into L3 larvae
Midges bite horse and deposit L3 larvae into bloodstream; migrate to nuchal lig as adults
Treatment of onchocerciasis
Ivermectin or moxidectin
What are aural plaques
Growths in pinna of ears due to papillomaviruses
These are progressive and don’t spontaneously regress
Which horses do we typically see warts from papillomaviruses in and how do we deal with them
Young horses 6 months - 4 years
Typically they spontaneously regress so leave alone
Which species cause ringworm in horses+ how to treat
Trichophyton (equinum, verrucosum) and microsporum (gypseum, equinum)
Identify which one via qPCR
Treat with topical enilconazole washes
What is cellulitis and which organisms typically cause it
Bacterial infection of the subcut tissue or deep dermis
Typically due to staphs or may be streps secondary to wound/puncture injury
Usually distal limb; can present with severe lameness
What infection can cause ‘paintbrush crusts’ of skin
Dermatophilus congolensis
= branching gram +ve facultative anaerobe
What would branching filaments of parallel cocci rows tell you was causing the skin issue
Dermatophilus congolensis
What is mud fever
PAstern dermatitis; syndrome with lots of potential causes
Treating staphylococcal pyoderma
Systemic antimicrobials can use flamazine topically too
What is urticaria
Hives
i.e raised circular wheals due to type 1 immune reaction
What are possible causes of urticaria
Immunological i.e insect bites, allergens in environment, food allergies, drugs
Non-immunological e.g cold/heat exposure, intense exercise, dermatographism
Treating urticaria in horses
Steroids if severe; do IV if extreme due to risk of resp tract obstruction
What is sweet itch
Insect bite hypersensitivity (culicoides midges)
= type 1 hypersensitivity
esp in icelandic ponies, shetland, welsh ponies
Should we advise against breeding a horse with sweet itch
Yes - there is a genetic ocmponent
What does atopy mean
Itchy skin disease due to cumulative allergens exceeding a pruritic threshold
What must we do before carrying out intradernal skin testing
Stop any medicated esp steroids for 2 weeks or so before testing
What are eosinophilic granulomas
Firm nodules of collagen degeneration below the skin with unknown aetiology
What is pemphigus foliaceus
Rare life threatning disease where the body forms auto-antibdies against keratinocyte proteins
Get pustules and blisters, itching, alopecia
Need steroids for life
Which breeds is chronic progressive lymphoedema seen mostly in
Heavy horse breeds e.g shites, clydesdales, freisians, cobs
How does chronic progressive lymphoedema work
Altered lymphatic function and elastin metabolism
cause progressive distal limb swelling and hypereratosis then get skin fold dermatitis, secondary infections etc
= welfare issue
Type 1 vs Type 2 photosensitisation
1 = primary due ot ingestion of photodynamic agents
2 = hepatogenous; due to liver disease preventing excretion of phylloerythrin (from chlorophyll)
What could cause liver disease and hepatogenous photosensitisation
Cholestasis
Mycotoxin ingestion
Ragwort ingestion
Cholestasis causes increased retension of phytoporphoryn in blood
What plant classically causes type 1 photosensitisation
St John’s wort
Are antihistamines useful in horses
Not really
Need high doses for an effect and then they get very drowsy
Where do we classically see sweet itch lesions in the UK and which syndrome is this
Syndrome 1; dorsal lesions esp on mane and tail head
