Skin Disorders Flashcards
General skin disorders characteristics
-time of year
-itching
-crusts, scales, loss of hair
-1 location or multiple
-what structures are involved
Causes of skin disorders:
-mange
-pediculosis
-onchocerca
-culicoides
-food allergy
-atopy
-dermatophytosis
-dermatophilosis
-folliculitis
-malassezia
-seborrhea
-pemphigus foliaceus
-papillomavirus
-habronema
-sarcoid
-sporotrichosis
-screwworm
Papillomavirus
cutaneous papillomas (warts) are proliferative skin lesions caused by equus caballus papillomavirus type 1 (EcPV-1)
What age does papillomavirus most effect?
most horses are <3 years old
How is papillomavirus spread?
by fomites or close contact
How long do papillomavirus warts last?
warts disappear spontaneously 1-6 months after they appear
Clinical findings of papillomavirus
-warts on muzzle, lips, sometimes distal limbs, ears, eyelids, genitalia
-cauliflower-like appearance
How is papilloma virus diagnosed?
obvious lesions, sometimes cutaneous biopsy to differentiate from verrucous sarcoids (older horses)
How is papilloma virus treated?
resolves spontaneously
-it is difficult to determine if therapy actually helps
When is treatment generally done for papillomavirus?
for esthetic reasons:
-freeze warts
-chemical cauterization
-surgical excision
-immunostimulants
How can papillomavirus be prevented?
affected horses should be isolated
-disinfect the premises and equiptment
What is dermatophilosis?
-rain rot
-mud fever
-dew poisoning
What is dermatophilosis caused by?
Dermatophilus congolensis:
falcultative anaerobic
shares characteristics with bacteria and fungus (hyphae and zoospores)
What is the natural habitat of dermatophilosis?
unknown
How can infections of dermatophilosis spread?
crusts from infected animals can infect the same animal on a different spot and other animals
What does the establishment of dermatophilosis infection depend on?
depends on the virulence of strain, health of horse, skin trauma, and moisture
What happens when dermatophilosis infections start?
-zoospores germinate, producing hyphae under favorable conditions
-hyphae penetrate the skin
-hyphae breaks down and forms coccoid cells
-those cells are released from the crusts to infect new areas
How does dermatophilosis survive?
D. congolensis break keratin and function at a wide pH range, enabling the disease to survive in inflammed skin
Can D. congolensis infect intact skin?
no
What makes skin susceptible to D. congolensis infection?
insects and ticks cause trauma making the skin susceptible to the infection
What is one of the main causes of dermatophilosis?
moisture
-rain increases blood sucking flies, creates moist environment under hairs with low oxygen
Clinical signs of dermatophilosis:
-lesions are exudative
-hairs are matted together forming thick crusts
-underlying skin under crusts is eroded, painful, and may bleed
-new lesions can be purulent and old lesions are dry and hairless
Where is dermatophilosis often found?
-rump
-dorsal thorax
-face
(from heavy rainfall)
-saddle area (when pad rubs and injures the skin)
How is dermatophilosis diagnosed?
cytology and clinical signs
Treatment of dermatophilosis
-parenteral administration of antibiotics (penicillin, SMZ-TMP)
-topical benzoyl peroxide shampoos (antibacterial and keratolytic, breaking down the crusts) (MTG, Kinetic products)
-most horses recover after 1 month of being kept at a dry place
Prevention of dermatophilosis:
-keep animals dry
-don’t share grooming tools
-insect repellent
-groom horse routinely to air out the skin
Dermatophytosis
ringworm
How long can fungus survive on an infected ringworm girth?
for 1 year
Is dermatophytosis contagious?
yes by indirect and direct contact
What % of horses with suspected ringworm actually have ringworm?
5%
-majority are dermatophilus or staph infection of the skin
What can lead to dermatophytosis lesions?
abrasions of the skin (important in heartgirth area)
What can predispose horses to dermatophytosis?
stress
What happens to some horses after a dermatophytosis infection?
they develop a strong immunity against it, they clear the infection and never develop it again
Lesion characteristics of dermatophytosis:
-may present with circular patches of alopecia
-surrounded by erythema and scaling
What may be observed in the early stages of dermatophytosis?
urticaria-like lesions
Where are the most frequent sites of dermatophytosis?
girth and shoulder
How is dermatophytosis diagnosed?
-cytology (bacteria, fungus)
-skin scraping (fungus, mange, other mites)
-histology (pemphigus foliaceus)
-culture of fungus
-determining what it isn’t first
How are most cases of dermatophytosis resolved?
spontaneously
Treatment of dermatophytosis:
-topical: povidine-iodine, 2% lime sulfur dip, ketoconazole shampoos
-bleach environment
-spray horses that were in contact with the infected horse
Is dermatophytosis zoonotic?
yes it can be passed to humans
Why are ketoconazole shampoos not very effective?
they have to sit for awhile on the skin in order to work, they no longer work after getting rinsed off
Urticaria (hives)
multiple plaque-like eruptions formed by localized edema (often develop and disappear suddenly)
Is hives exogenous or endogenous?
both
What can exogenous hives be produced by?
toxic irritating products of the stinging nettle, the stings or bites of insects, medications, or chemicals
What can endogenous hives be produced by?
after inhalation or absorption of ingested allergens
What can hives be associated with?
intestinal parasites
How can present as urticaria (hives) early in the disease?
-dermatophytosis (ringworm)
-pemphigus foliaceus
Clinical signs of urticaria (hives)
-plaques appear within a few minutes or hours of exposure to the causative agent
-horses are often excitable or restless
-skin lesions are elevated, round, flat-topped, and may be slightly depressed in the center
-on any part of the body
-lesions disappear as rapidly as they arise (usually within a few hours)
-prognosis is favorable
-fatalities are rare
Clinical signs of severe cases of urticaria (hives)
-the cutaneous eruptions are preceded by fever, anorexia, or dullness
-they may be found on the mucous membranes of the mouth, nose, conjunctiva, rectum, and vagina
-death due to anaphylaxis
What is the treatment of acute urticaria?
it usually disappears spontaneously
Treatment of uticaria:
-dexamethasone
-antihistamines (Rocover-Kinetic)
-epinephrine to combat anaphylactic shock
-lesions will return if the allergen is not eliminated
