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Bacterial dermatitis is ALWAYS...
secondary to another process, which may be metabolic, immunologic, cutaneous!!
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Occurence of bacterial dermatitis is linked to... (3)
poor nutrition and husbandry, season, physical trauma (abrasions, insect bites)
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What is the etiology of dermatophilosis?
Dermatophilus congolensis, gram + facultative anaerobe actinomycete
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What are the 3 conditions for dermatophilosis to cause disease?
carrier animal (chronically infected), moisture, skin abrasions (clipping, insect bites, trauma)
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Dermatophilosis usually has a(n) ___________ distribution and lesions include...
dorsum and legs; follicular and tufted papules, removal of crusts exposes erythematous skin with suppurative material +/- ulceration
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What is the chronic presentation of dermatophilosis?
moth-eaten haircoat (loss of suppuration, left with thick crust and alopecia)
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What other signs may be present with dermatophilosis (other than skin lesions)? (3)
fever, lymphadenopathy, pain associated with removal of crusts
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How is dermatophilosis diagnosed?
microscopic examination of impression smear made from fresh scab, exudate: rows of coccoid bodies, termed "branching railroad organism"
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Describe the treatment of dermatophilosis? (3)
- remove to wet weather, remove crusts with care (painful, contagion), bathes with 2% chlorhexidine (+/- salicylic acid mixed in) daily for a week
- [systemic pen G RARELY required]
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What are common ringworm agents in horses? (4)
Trichophyton equinum (most common), Microsporum equinum, T. mentagrophytes, T. verrucosum
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What are characteristics of infection with ringworm in horses? (3)
- usually animals <2 years old
- tranmitted by contact with infected carriers, fomites, or soil
- Fall/ winter
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What is the major presenting different between dermatophilosis and dermatophytosis?
- Dermatophilosis starts dorsally
- Dermaophytosis starts in the girth and thorax area
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What are predisposing factors to dermatophytosis? (2)
- damp/ crowded/ dark stalls
- debilitation/ malnutrition
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What are clinical signs of ringworm? (4)
- focal, sharply demarcationscaling or crusting
- tufted papules (saddle and girth area)
- chronic- thick crusts, moth-eaten alopecia
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How is ringworm diagnosed? (3)
- DTM
- T. verrucosum doesn't grow on DTM, so if your horses are around cattle, tell the microbiologist
- add niacin to grow T. equinum
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What is the treatment for ringworm? (4)
- may resolve spontaneously in sunshine 6-12 weeks
- isolation to limit spread, treat ALL in contact horses
- topical lime sulfur or chlorhex with an -azole
- treat environment with Enilconazole, undiluted bleach works but is corrosive
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What is the most common immune-mediated dermatosis in horses, and how is it unique?
pemphigus foliaceous; affects foals 6 months- 1 year old
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What is important to know about pemphigus in horses? (2)
- lesions exacerbated by sun and humid warm weather
- signs wax and wane- fever, anorexia
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What lesions are present with pemphigus foliaceous in horses? (6) What other clinical signs accompany these lesions? (5)
- primary lesions (not usually seen)- pustules, vesicles
- urticaria, alopecia, scaling, crusts
- edema of ventrum and distal limbs, fever, weight loss, lethargy, depression
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How is pemphigus foliaceous diagnosed? (2)
- Impression smears show acantholytic cells (increases suspicion)
- Definitive- biopsy under crusts for histopathology and bacterial and fungal cultures
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Describe the reaction pattern associated with pastern dermatitis. (3)
plantar/ palmar aspects of pastern, bulbs of heels, +/- extension to mid-cannon
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Pastern dermatitis is preceded by...
mechanical injury to the stratum corneum.
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Early clinical signs of pastern dermatitis. (7)
- [depends on etiology and stage of dz]
- bilaterally symmetrical hind limbs- crusts, alopecia, seborrhea, hyperkeratosis, hyperplastic plaques, +/- pruritus and pain
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What is the most common signalment associated with pastern dermatitis?
heavy draft breeds most common, mean age of onset 9 years
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Chronic clinical signs of pastern dermatitis. (11)
- PROLIFERATIVE FORM
- excessive granulation tissue, nodular proliferations of hyperkeratosis, distal limb edema, lameness, greasiness, malodor, erosion, ulceration, fissures, +/- cellulitis
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How can you categorize factors that lead to pastern dermatitis? (3)
- factors/ patient characteristics that provide the basis for development of PD
- factors that initiate dermatitis (primary disease etiologies)
- features of the dermatitis that maintain, reinforce, and strength the disease process
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What chronic, inherited condition of draft breeds should be a high differential for pastern dermatitis?
chronic progressive lymphedema- insufficient lymphatic transport due to unidentified genetic mutation possibly in elastin gene--> increased degradation of vessels--> disfigurement, disability of legs, premature death
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Describe the diagnostic plan for pastern dermatitis. (7)
superficial and deep skin scrapes, cytology, DTM, tissue biopsy for culture +/- histopath, CBC/Chem (helps r/o hepatogenous photosensitization and vasculitis)
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What nursing care measures can be taken for animals with pastern dermatitis? (4)
- debridement- remove crusts, hair with keratolytic/plastic shampoos; blot dry (don't rub!)
- for exudative, use astringents
- dry environment
- keep out of UV light until you r/o photosensitization
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What advice should you give the owner of a horse with pastern dermatitis? (5)
- takes time to get primary dx
- some cases are idiopathic
- address stable management
- likely to recur if they aren't diligent
- can require lifelong txt
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