Derm3- Equine Dermatoses

  1. Bacterial dermatitis is ALWAYS...
    secondary to another process, which may be metabolic, immunologic, cutaneous!!
  2. Occurence of bacterial dermatitis is linked to... (3)
    poor nutrition and husbandry, season, physical trauma (abrasions, insect bites)
  3. What is the etiology of dermatophilosis?
    Dermatophilus congolensis, gram + facultative anaerobe actinomycete
  4. What are the 3 conditions for dermatophilosis to cause disease?
    carrier animal (chronically infected), moisture, skin abrasions (clipping, insect bites, trauma)
  5. 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
  6. What is the chronic presentation of dermatophilosis?
    moth-eaten haircoat (loss of suppuration, left with thick crust and alopecia)
  7. What other signs may be present with dermatophilosis (other than skin lesions)? (3)
    fever, lymphadenopathy, pain associated with removal of crusts
  8. How is dermatophilosis diagnosed?
    microscopic examination of impression smear made from fresh scab, exudate: rows of coccoid bodies, termed "branching railroad organism"
  9. 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]
  10. What are common ringworm agents in horses? (4)
    Trichophyton equinum (most common), Microsporum equinum, T. mentagrophytes, T. verrucosum
  11. 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
  12. What is the major presenting different between dermatophilosis and dermatophytosis?
    • Dermatophilosis starts dorsally
    • Dermaophytosis starts in the girth and thorax area
  13. What are predisposing factors to dermatophytosis? (2)
    • damp/ crowded/ dark stalls
    • debilitation/ malnutrition
  14. What are clinical signs of ringworm? (4)
    • focal, sharply demarcationscaling or crusting
    • tufted papules (saddle and girth area)
    • chronic- thick crusts, moth-eaten alopecia
  15. 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
  16. 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
  17. What is the most common immune-mediated dermatosis in horses, and how is it unique?
    pemphigus foliaceous; affects foals 6 months- 1 year old
  18. What is important to know about pemphigus in horses? (2)
    • lesions exacerbated by sun and humid warm weather
    • signs wax and wane- fever, anorexia
  19. 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
  20. How is pemphigus foliaceous diagnosed? (2)
    • Impression smears show acantholytic cells (increases suspicion)
    • Definitive- biopsy under crusts for histopathology and bacterial and fungal cultures
  21. Describe the reaction pattern associated with pastern dermatitis. (3)
    plantar/ palmar aspects of pastern, bulbs of heels, +/- extension to mid-cannon
  22. Pastern dermatitis is preceded by...
    mechanical injury to the stratum corneum.
  23. 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
  24. What is the most common signalment associated with pastern dermatitis?
    heavy draft breeds most common, mean age of onset 9 years
  25. Chronic clinical signs of pastern dermatitis. (11)
    • excessive granulation tissue, nodular proliferations of hyperkeratosis, distal limb edema, lameness, greasiness, malodor, erosion, ulceration, fissures, +/- cellulitis
  26. 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
  27. 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
  28. 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)
  29. 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
  30. 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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Derm3- Equine Dermatoses
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