Bacterial dermatitis is ALWAYS...
secondary to another process, which may be metabolic, immunologic, cutaneous!!
Occurence of bacterial dermatitis is linked to... (3)
poor nutrition and husbandry, season, physical trauma (abrasions, insect bites)
What is the etiology of dermatophilosis?
Dermatophilus congolensis, gram + facultative anaerobe actinomycete
What are the 3 conditions for dermatophilosis to cause disease?
carrier animal (chronically infected), moisture, skin abrasions (clipping, insect bites, trauma)
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
What is the chronic presentation of dermatophilosis?
moth-eaten haircoat (loss of suppuration, left with thick crust and alopecia)
What other signs may be present with dermatophilosis (other than skin lesions)? (3)
fever, lymphadenopathy, pain associated with removal of crusts
How is dermatophilosis diagnosed?
microscopic examination of impression smear made from fresh scab, exudate: rows of coccoid bodies, termed "branching railroad organism"
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]
What are common ringworm agents in horses? (4)
Trichophyton equinum (most common), Microsporum equinum, T. mentagrophytes, T. verrucosum
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
What is the major presenting different between dermatophilosis and dermatophytosis?
- Dermatophilosis starts dorsally
- Dermaophytosis starts in the girth and thorax area
What are predisposing factors to dermatophytosis? (2)
- damp/ crowded/ dark stalls
- debilitation/ malnutrition
What are clinical signs of ringworm? (4)
- focal, sharply demarcationscaling or crusting
- tufted papules (saddle and girth area)
- chronic- thick crusts, moth-eaten alopecia
How is ringworm diagnosed? (3)
- T. verrucosum doesn't grow on DTM, so if your horses are around cattle, tell the microbiologist
- add niacin to grow T. equinum
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
What is the most common immune-mediated dermatosis in horses, and how is it unique?
pemphigus foliaceous; affects foals 6 months- 1 year old
What is important to know about pemphigus in horses? (2)
- lesions exacerbated by sun and humid warm weather
- signs wax and wane- fever, anorexia
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
How is pemphigus foliaceous diagnosed? (2)
- Impression smears show acantholytic cells (increases suspicion)
- Definitive- biopsy under crusts for histopathology and bacterial and fungal cultures
Describe the reaction pattern associated with pastern dermatitis. (3)
plantar/ palmar aspects of pastern, bulbs of heels, +/- extension to mid-cannon
Pastern dermatitis is preceded by...
mechanical injury to the stratum corneum.
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
What is the most common signalment associated with pastern dermatitis?
heavy draft breeds most common, mean age of onset 9 years
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
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
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
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)
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
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