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Flashcards in skin disorders Deck (17)
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what is papillomavirus?

cutaneous papillomas (warts) are proliferative skim lesions caused by equus caballus papillomavirus type 1, most horses are


clinical signs of papillomavirus

warts on muzzle, lips, occasionally in distal limbs, ears, eyelids and genitalia, cauliflower like appearance, diagnosed by obvious lesions or sometimes cutaneous biopsy to differentiate from verrucous sarcoids


treatment of papillomavirus

resolve spontaneously, difficult to know if any therapy actually helps, may freeze warts, chemical cauterization, surgical excision or immunostimulants


what is dermatophilosis?

rain rot, mud fever, dew poisoning caused by dermatatophilus congolnesis (facultative anaerobic, shares characteristics with bacteria and fungus), unknown natural habitat, crusts from the infected animal can infect the same animal on a different spot and other animals


establishment of dermatophilosis infection

depends on virulence of strain, health of the horse, skin trauma, moisture
zoospores germinate, producing hyphae under favorable conditions, hyphae break down and produce coccoid cells which are released from the crusts and infect new areas
d. congolnesis break keratin and function at a wide pH range, enabling them to survive in inflamed skin


what does d. congolnesis infect?

unable to infect intact skin, insects and ticks cause trauma, making skin susceptible to the infection, rain increases blood sucking flies, creates a moist environment under hairs with low oxygen


clinical signs of dermatophilosis

lesions are exudative, hairs are matted together forming thick crusts. when crusts are removed the underlying skin is eroded, painful and may bleed. New lesions can be purulent, where as old lesions are dry and hairless


location of dermatophilosis

rump, dorsal thorax, face, saddle area, diagnosed by cytology and clinical signs


treatment and prevention of dermatophilosis

keep animal dry, most horses recover after being kept in a dry place for 1 month, use topical benzoyl peroxide shampoos (antibiotic and keratolytic) to break down the crusts, should be left on skin for 15 minutes before rinsing. do not excessively scrub (leads to new lesions), Mtg and other products may be used, parenteral administration of antibiotics (penicillin, SMZ-TMP), don't share grooming tools, insect repellent, groom horse routinely to air out skin


what is dermatophytosis?

ring worm (round lesions), highly contagious through direct or indirect contact, fungus can survive for 1 year, study showed only 5% of horses that appear to have ringworm actually have it, majority are staph infection of the skin


how do horses get dermatophytosis?

abrasions of skin may lead to lesions (important in heart girth area), stress may predispose (32% of animals in training are clinically infected and 1% of breeding animals are infected), some horses develop a strong immunity against dermatophyte, clear the infection and never develop it again


how is dermatophytosis diagnosed

lesions may present with circular patches of alopecia, surrounded by erythema and scaling, urticaria-like lesions may be observed in early stages, most frequent sites: girth and shoulder
diagnosed with cytology, skin scraping, histology, culture of fungus


treatment of dermatophytosis

most cases resolve spontaneously, topical povidone-iodine, 2% lime sulfur (LymDyp), shampoos (not very effective because of residual effect), all horses that share space with infected horses should be sprayed because they may be silent carriers. bleach (1:40) premises and tack, can be contagious to humans


what is urticaria?

multiple plaque-like eruptions formed by localized edema-often develop and disappear suddenly, may be exogenous or endogenous, exogenous ehives may be produced by toxic irritating products of the stinging nettle, the stings or bites of insects, medications or chemicals


endogenous urticaria

after inhalation or absorption of ingested allergens, may be associated with intestinal parasites, ringworm and pemphigus foliates may present as urticaria early in the disease


clinical sings of urticaria

plaques appear within a few minutes or hours of exposure to the causative agent, in severe cases the cutaneous eruptions are preceded by fever/anorexia/dullness, horses often become excited and restless, the skin lesions are elevated, round, flat-topped and may be slightly depressed in the center, any part of the body, in severe cases lesions may appear in mucous membranes of mouth/nose/conjunctiva, rectum and vagina, lesions disappear usually within a few hours, prognosis is favorable, fatalities are rare but may be due to anaphylaxis


treatment of urticaria

acute urticaria usually disappears spontaneously, dexamethasone, antihistamines (questionable value), epinephrine may be given for anaphylactic shock, lesions disappear fast, but return if allergen is not eliminated