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Equine Dermatology

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Title: Equine Dermatology


1
Equine Dermatology
  • Nodular Skin Diseases

2
What are the major causes of Nodules?
3
What are the major causes of Nodules?
  • Inflammatory
  • Parasites
  • Collagenolytic Granulomas/Eosinophilic Granulomas
  • Habronema
  • Hypoderma
  • Tick bite granulomas
  • Infections (Fungal/Fungal-like)
  • Sporotrichosis
  • Phaeophymycosis
  • Eumycotic mycetomas
  • Zygomycosis
  • Other mycoses (dermatophyte kerion, blasto,
    crypto)
  • Pythiosis

4
What are the major causes of Nodules?
  • Inflammatory
  • Infections (Bacterial)
  • Furunculosis
  • Dermatophilosis
  • Ulcerative lymphangitis (Corynebacterium
    pseudotuberculosis)
  • Actinomycosis
  • Nocardiosis
  • Abscesses
  • Mycobacterial infections (TB)
  • Glanders

5
What are the major causes of Nodules?
  • Inflammatory
  • Viral
  • Vaccinia
  • Immunologic
  • Urticaria
  • Erythema multiforme
  • Amyloidosis

6
What are the major causes of Nodules?
  • Inflammatory
  • Miscellaneous
  • Dermoid/follicular cysts
  • Eosinophilic granulomas
  • Axillary nodular necrosis
  • Unilateral papular dermatosis
  • Exuberant granulation tissue
  • Panniculitis
  • Hematoma
  • Foreign body granulomas

7
What are the major causes of Nodules?
  • Neoplastic
  • Papilloma
  • Aural plaque
  • Squamous cell carcinoma
  • Sarcoid
  • Melanoma/melanocytoma
  • Mast cell tumor
  • Basal cell tumor
  • Fibroma/fibrosarcoma
  • Hemangioma/hemangiosarcoma
  • Lipoma
  • Lymphoma
  • Malignant fibrous histiocytoma

8
What are the basics of diagnosis?
9
What are the basics of diagnosis?
  • Signalment
  • History
  • Location and progression of the lesions(s)
  • Cytology/FNA
  • Biopsy (histopath, bacterial fungal culture)

10
23 yr Percheron Gelding
11
chief complaint nodules on penis and prepuce
12
Differential diagnosis?
13
Differential diagnosis
  • Melanomas
  • Inflammatory granulomas

14
Diagnostic Plan
  • Fine Needle Aspirate
  • Biopsy
  • Abdominal palpation/ultrasound exam for evidence
    of metastasis

15
Clinical Management
  • Observation
  • Cimetidine 5 mg/kg q 12 hrs for gt 3 months
  • ? intratumoral chemotherapy with cisplatin
  • ? immunotherapy with BCG

16
6 yr AQHA Mare Ulcerated nodule at medial canthus
17
Differential diagnosis?
18
Differential diagnosis
  • Inflammatory
  • Habronema
  • Fungal (histo, sporo)
  • Post injury exuberant granulation tissue
  • Neoplastic
  • Sarcoid
  • Squamous cell carcinoma
  • Basal cell carcinoma
  • Mast cell tumor

19
Diagnostic Plan
  • Impression smear cytology
  • Biopsy
  • Histopath
  • Fungal bacterial culture

20
Results
  • Cytology
  • Numerous eosinophils and macrophages
  • Histopath
  • Eosinophilic dermatitis with intralesional larvae

21
Clinical Management
  • Corticosteroids to decrease inflammation
  • 600 mg pred daily x 10 days then 300 mg daily for
    another 10-14 days
  • Fly mask to protect from flies
  • Ivermectin orally
  • Topical corticosteroid-antibiotic ointment or
    cream (ophthalmic)

22
8 yr AQHA Gelding
23
Differential diagnosis?
24
Differential diagnosis
  • Inflammatory
  • Habronema
  • Fungal (histo, sporo)
  • Post injury exuberant granulation tissue
  • Neoplastic
  • Sarcoid
  • Squamous cell carcinoma
  • Basal cell carcinoma
  • Mast cell tumor

25
Diagnostic Plan
  • Impression smear cytology
  • Biopsy
  • Histopath
  • Fungal bacterial culture

26
Fibroblastic Sarcoid
  • Probable viral etiology (related to bovine
    papillomaviruses)
  • Types
  • Verrucous (wart-like)
  • Fibroblastic (proud flesh-like)
  • Mixed
  • Occult (flat)

27
Management Options
  • Cyrosurgery
  • CO2 Laser Surgery
  • Intralesional cisplatin
  • Intralesional BCG
  • Topical Imiquimod (Aldara)
  • Topical XXTERRA (bloodroot ZnCl)

28
14 yr Paso Fino Mare
29
Presenting Complaint
  • Inspiratory stridor
  • Mass in right nostril
  • Also has partial alopecia over withers and
    thickening of skin in that region

30
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31
Differential diagnosis?
32
Differential diagnosis
  • Inflammatory
  • Bacterial infections
  • Fungal infections
  • Amyloidosis
  • Neoplastic
  • Lymphosarcoma
  • Fibroma/fibrosarcoma
  • Mast cell tumors

33
Diagnostic Plan
  • Impression smears/FNA
  • Biopsies
  • Histopath
  • Bacterial Fungal Cultures

34
Amyloidosis
  • May be primary or secondary to chronic infections
  • Primary is most likely when the skin and upper
    respiratory tract are affected
  • Fibrils are composed of AL amyloid (monoclonal
    immunoglobulin light chains)

35
Amyloidosis Clinical Management
  • Treat secondary infections
  • Surgical excision of nodules interfering with
    respiration
  • ? Topical DMSO (may promote amyloid degradation)

36
10 yr AQHA gelding
37
Differential Diagnoses?
38
Differential Diagnoses
  • Inflammatory
  • Bacterial granulomas
  • Dermatophyte kerions
  • Warbles
  • Tick bite granulomas
  • Erythema multiforme
  • Dermoid/follicular cysts
  • Eosinophilic granulomas
  • Collagenolytic granulomas
  • Panniculitis

39
Differential Diagnoses
  • Neoplastic
  • Basal cell tumors
  • Hair follicle tumors
  • Mast cell tumors

40
Diagnostic Plan
  • FNA
  • Biopsy
  • Histopath
  • Bacterial fungal cultures

41
Histopath
  • Multiple foci of collagenolysis
  • Inflammatory infiltrate is predominantly
    eosinophilic
  • No larval fragments

42
Collagenolytic Granulomas/Eosinophilic Granulomas
  • Most common in spring summer
  • Most common on back, withers and neck
  • Not painful or pruritic
  • Likely a consequence of fly or mosquito bites

43
Clinical Management
  • Observation
  • Surgical excision
  • Sublesional injections of triamcinolone acetonide
    (3-5 mg/lesion) repeated q 2 wks for max of 3
    times
  • Fly mosquito control (fly sheets/repellants)

44
24 yr AQHA gelding
45
Differential Diagnosis?
46
Differential Diagnoses
  • Inflammatory
  • Bacterial granulomas (dermatophilosis)
  • Dermatophyte kerions
  • Warbles
  • Tick bite granulomas
  • Erythema multiforme
  • Dermoid/follicular cysts
  • Eosinophilic granulomas
  • Collagenolytic granulomas
  • Panniculitis

47
Differential Diagnoses
  • Neoplastic
  • Basal cell tumors
  • Hair follicle tumors
  • Mast cell tumors
  • Sarcoids

48
Diagnostic plan
  • Impression smears/FNA
  • Biopsies
  • histopathology
  • Fungal and bacterial culture

49
Cytology
50
Dermatophilosis Clinical Management
  • Keep dry
  • Remove crusts (2-4 chlorhexidine shampoo)
  • Chlorhexidine cream or spray daily
  • If does not resolve with topical treatment
    systemic penicillin or oral TMS until lesions
    resolve

51
12 yr Clydesdale gelding
52
Differential Diagnosis?
53
Differential Diagnoses
  • Inflammatory
  • Bacterial granulomas
  • Fungal granulomas/dermatophyte kerions
  • Tick bite granulomas
  • Eosinophilic/collagenolytic granulomas

54
Differential Diagnoses
  • Neoplastic
  • melanocytomas
  • lymphosarcoma
  • Basal cell tumors
  • Hair follicle tumors
  • Mast cell tumors

55
Diagnostic Plan
  • Cytology/FNA
  • Biopsies
  • Histopathology
  • Bacterial and fungal cultures

56
Sporotrichosis
  • Iodides
  • NaI 20-40 mg/kg IV for 2-5 days then orally until
    cured
  • KI 1-2 mg/kg PO daily for 1 wk then 0.5-1 mg/kg
    daily until cured
  • Iodism scaling, alopecia, depression, anorexia,
    lacrimation, salivation
  • Itraconazole
  • 5 mg/kg PO daily

57
9 yr TB mare
58
Differential Diagnoses?
59
Differential Diagnoses
  • Inflammatory
  • Infectious bacterial, fungal, parasitic,
    pythiosis
  • Post traumaticexuberant granulation tissue
  • Parasitichabronema, hypoderma
  • Neoplastic
  • Squamous cell, sarcoid, mast cell tumor,
    malignant fibrous histiocytoma

60
Diagnostic Plan
  • Cytology
  • Biopsy
  • Histopathology
  • Bacterial fungal cultures

61
Fistulous Withers
  • Inflammation of the supraspinous bursae
  • Ruptures and drains a clear or purulent fluid
  • Occasionally associated with Brucella abortus or
    occasionally B suis infection
  • Run an agglutination titer for Brucella

62
Fistulous withers clinical management
  • Surgical debridement (remove infected bursa)
  • Systemic antibiotics based on CS
  • ?? Vaccinate with strain 19 brucella SQ or IV ??

63
4 yr old Belgian gelding
64
Differential diagnoses?
65
Differential Diagnoses
  • Inflammatory
  • Bacterial (especially Corynebacterium
    pseudotuberculosis)
  • Fungal (especially Basidiobolomycosis)
  • Pythiosis
  • Exuberant granulation tissue
  • Neoplastic
  • Fibroma/fibrosarcoma
  • Sarcoid
  • Squamous cell carcinoma

66
Diagnostic Plan
  • Cytology
  • Biopsy
  • Histopathology
  • Bacterial fungal cultures

67
Pythiosis
68
Pythiosis Clinical management
  • Surgical excision/debulking (laser?)
  • Immunotherapy with vaccine prepared from Pythium
    hyphal extract (2 ml SQ weekly for at least 3
    treatments)
  • Itraconazole Terbinafine are effective in
    20 of dogs but
  • Do not allow horses to stand in ponds!

69
Ventral Midline of 14 yr Tennessee Walker gelding
70
Differential Diagnoses?
71
Differential Diagnoses
  • Horn fly hypersensitivity
  • Culicoides hypersensitivity
  • Dermatophilosis
  • Dermatophytosis
  • Pelodera dermatitis
  • Onchocerciasis (? Usually dorsal)
  • Contact dermatitis
  • Bacterial pyoderma

72
Diagnostic Plan
  • Cytology
  • Skin scrapings
  • Biopsy
  • Histopathology
  • Bacterial fungal cultures
  • Intradermal skin testing for hypersenstivity to
    Culicoides and Horn Flies (Haemotobia irritans)

73
Results
  • Eosinophilic Dermatitis
  • 4 reaction to Culicoides

74
Ventral Midline Dermatitis Management
  • Topical corticosteroids /- antibiotics
  • Protect from gnats and flies
  • Check stable hygiene (remove straw bedding if
    diagnose Pelodera)

75
Culicoides Preventative strategies
  • Stable dusk to dawn
  • Fans in stalls
  • 32 mesh screens
  • Insecticides and repellants
  • Eliminate standing water (breeding areas for the
    gnats)

76
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