L6 - Viral, Bacterial - Mycotic Skin Dz PDF

Integumentary system: Lecture 5 Contents  5.1 Viral diseases of skin  5.2 Bacterial diseases of skin  5.3 Mycotic diseases of skin - Superficial mycoses - Deep mycoses  5.1 Viral diseases  Intact integument is resistant to viral penetration  Prerequ...

Integumentary system: Lecture 5 Contents  5.1 Viral diseases of skin  5.2 Bacterial diseases of skin  5.3 Mycotic diseases of skin - Superficial mycoses - Deep mycoses  5.1 Viral diseases  Intact integument is resistant to viral penetration  Prerequisite for infection: eg. antropod bite / wound  Local: eg papovaviridae (papillomas)- epitheliotropic Systemic (viremia): eg. FMD, canine distemper, both Both cutaneous & systemic: poxvirus (poxviridae)  Lesions: origin not moplasian > - junto lesson a moplastic like -  Neoplastic: eg. Papilloma  Proliferative: eg. Poxvirus, Contagious ecthyma  Vesicular: eg. FMD, Vesicular exanthema  Viral diseases : Papilloma virus  Types: squamous papilloma, fibropapilloma. Eg: Papilloma in a dog  Gross; flat, raised, crusty, fissured, horny mass attached to the skin by a narrow or broad pedicle  Histo: mixtures of epidermal and dermal proliferation eg. squamous type; markedly thickened epidermis (hyperplasia; S. spinosum & corneum), hyperkeratosis, hydropic degeneration, inclusion bodies (rare; intracytoplasmic or intranuclear) Viral diseases : Papilloma  Viral diseases : Pox viral infection  Gross: erythematous macules - papular - vesicular -umbilicated pustules- pustule rupture – ulcer - crust (heal - scar)  Histo: epidermal cytoplasmic swelling vacuolation, multiloculated vesicles. Dermal: edema, vascular dilatation, perivascular mononuclear-cell infiltrate, & variable neutrophil infiltrate  Typical pox phases (vesicles / pustules / crusts) but more hyperplastic / proliferative  Others: crust, hyperkeratosis colonized by surface bacteria, intracytoplasmic inclusion bodies  Viral diseases interest balrowing plasmic animativ inclusion - - - body  Ballooning degeneration and intracytoplasmic inclusion bodies  Viral diseases shin startin vehagena tran anaty all casting  Schematic diagram of the development of a poxvirus lesion over time 9thS Viral diseases : Contagious ecthyma immere  A.k.a. Contagious Pustular Dermatitis  Gross: cutaneous abrasion, vesicular (transient), pustules (flat), layer of brown-gray crust - regression or epithelial proliferation & papillomatous growths  Histo: ???  marked proliferative keratinocytes, acanthosis, vacuolation/spongiosis of epidermal, intraepidermal microabscess, intracytoplasmic inclusion bodies. Dermal: superficial oedema, marked capillary dilatation, perivascular mononuclear infiltration  Viral diseases : Contagious ecthyma Scale  Lesions: vesicles-pustules-crust at feet and oral cavity such as eyelids, mouth; rarely GI tract / viscera localisi lessin Viral diseases : Contagious ecthyma Incanthosis] Viral diseases : Contagious ecthyma Haired skin, lip commissure. Epithelial hyperplasia (*) with increased thickness up to 10x normal (acanthosis) with prominent intracellular clear spaces/bridging (spongiosis), and a vesicle (arrow). Inset: rarely keratinocytes contain one or more 2–10 µm round, brightly eosinophilic intracytoplasmic inclusion bodies (arrowheads). * -> sathosis - > intracytoplastic Inclusi bodice Viral diseases : Foot and mouth disease  Viral diseases : Vesicular exanthema  Formation of vesicles on the snout, oral mucosa, soles of the feet, coronary band, and between the toes. VPM 3417: VETERINARY PATHOLOGY III  Pro Viral diseases : Canine distemper Raccoon – scale/crust on distal limbs “Hard pad” 5.2 Bacterial diseases  Intact integument remarkably resistant to bacteria invasion: lack of moisture, constant desquamation, pressures exerted by the normal flora induce damage  Skin barrier damaged: bacteria from the transient flora & occasionally the resident flora may assume pathogenicity Bacterial diseases  Factors that assist bacteria colonization and invasion such as:  Continued moisture (leading to maceration of the S. corneum & leaching of the protective lipid coat)  Alterations in keratinization  Frictional damage and physical irritation (parasites & their secretion)  Accumulated dirt and excess sweating  Direct trauma  Bacterial diseases : Pyoderma  Canine skin fold pyoderma  Bacterial diseases - Pyoderma  2o pyoderma: occur in disease skin, cause by more than one bacterial spp. variable clinical appearance eg. ectoparasitism and seborrheic condition  Superficial pyoderma: involve epidermis, usually heal without scarring, short duration, not associated with systemic illness  Lesions: papules, transient pustules, crust  Histo: intraepidermal pustular dermatitis or/and superficial folliculitis.  Eg. Impetigo (subcorneal pustular dermatitis due to Staphylococcus aureus, Dermatophilosis due to Dermatophilus congolensis)  Bacterial diseases : Superficial pyoderma  Erythematous pustular dermatitis  Bacterial diseases : Deep pyoderma  Deep pyoderma: involve the dermis, with or without the subcutis, often heal with scarring, chronic, sometimes recurrent course, may involve regional lymph node & systemic illness  Lesions: papules or pustules, subcutaneous nodules, abscesses, ulcers or fistulous tracts  Histo: deep folliculitis, nodular to diffuse suppurative or pyogranulomatous dermatitis. Examples: - Feline leprosy due to Mycobacterium lepraemurium - Footrot due to Fusobacterium necrophorum  Bacterial diseases  Canine impetigo  Bacterial skin infection forming pustules and yellow crusty sores  Predisposed by moist / dirty environments, abrasions, parasitism, poor nutrition  Superficial pustular dermatitis  Bacterial diseases Canine impetigo  Bacterial diseases Dermatophilosis in ruminants  a superficial exudative dermatitis, seen most commonly in hot and humid areas  Bacterial diseases : Dermatophilosis  Characteristic branching filaments of D. congolensis; filaments undergo longitudinal & transverse septation to form parallel rows of coccoid bodiesa  Bacterial diseases Feline acne: a. Hair follicle in telogen. b. The hair has been shed and a corned ploys the follicular orifice. The epidermis is slightly acanthotic and a mild perifollicular infiltrate forms. c. As bacteria (black dots) invade the follicle, acanthosis and inflammation increase. The follicle dilates, and a pustule begins to form. At the same time the comedo disintegrates. d. Pustule formation is complete. The thin crust at the former follicular opening is breaking away as the first drop of pus oozes out. The former follicle is now a small intradermal abscess surrounded by a dense inflammatory infiltrate. This represents the severe form of feline acne on the chin. „544-4i, I:.  Bacterial diseases Canine pyotraumatic dermatitis  Intense pruritus, self- trauma and secondary bacterial infection  Focal alopecia, excoriation (erosion / ulceration), exudative lesion  Bacterial diseases “Diamond Skin Disease” in pig with Swine Erysipelas  Note rhomboid / diamond shaped erythematous plaques typical of infection with Erysipelothrix rhusiopathiae  Bacterial diseases Salmonellosis or other endotoxemias  Venous infarction of extremities due to endotoxin induced venous thrombosis  5.3 Mycotic diseases Superfical mycoses: Invade skin to a very limited extent; growth only in the non viable keratinized tissue  Dermatomycosis or dermatophytosis : eg. Microsporum spp. & Trichophyton spp.  Do not invade living tissue, but remain confined to the keratinized layers. The branching septae hyphae colonize the surface s. corneum, the follicular infundibula & hair shafts.  Gross: erythema, folicular papules, scaling, crusting & alopecia (alopecia due to breakage of the brittle, & is not permanent unless a secondary bacterial folliculitis destroys the root of the hair follicle)  Mycotic diseases Superfical mycoses  Classical lesions is circular patch of alopecia, with peripheral expansion and central healing producing the "ring“ appearance  Histo: contact irritant dermatitis (initial) – epidermal hyperplasia (acanthosis), ortho- and parakeratotic hyperkeratosis, exocytosis of neutrophils, intracorneal microabscess, organism around the hair shaft Mycotic diseases Dermatophytosis  A.k.a. ringworm  Common / worldwide distribution  Mainly Microsporum & Trichophyton in young/ immunocompromised animals  Predisposing factors include overcrowding, high humidity, poor sanitation / nutrition  Contagious direct or fomites attacks keratinized layers, cause inflammation  Mycotic diseases Dermatophytosis  Circular patches of scaling / alopecia to papules / pustules / furunculosis / crusting  Canine pinna: focal alopecia, erythema and scaling VPM 3417: VETERINARY PATHOLOGY III  Mycotic diseases Dermatophytosis  Circular patches of scaling / alopecia to papules / pustules / furunculosis / crusting bovine head  Multifocal alopecia with scaling/crusting  Mycotic diseases Dermatophytosis  Multiple to coalescing areas of alopecia with scale & crust  Mycotic diseases Dermatophytosis  One study indicated ~50% of people exposed to either symptomatically or asymptomatically infected cats develop lesions  Arthrospores surrounding and hyphae within hair shaft Mycotic diseases Dermatomycosis. a. Normal hair follicle. b, There is invasion of the hair follicle by a dermatophyte. Mycelia and spores can be seen affecting only the keratinized portions of the skin and appendages. There are acanthosis and inflammatory infiltration. The third hair is broken off, but hair roots are intact. Fungi are growing downward on the hair, stopping at Adamson's fringe—a zone just above the area of keratin synthesis. No fungi can be seen in the living cells of the dermis or epidermis. c, Secondary bacterial infection has caused partial destruction of the hair a, follicle. Hairs have been lost, a follicular plug has formed and crusts appear on the epidermal surface. The general histologic picture is that of a subacute to chronic dermatitis  Mycotic diseases Subcutaneous or intermediate mycoses  Mostly saprophytic fungi, introduced into the s/c by penetrating cutaneous wounds Sporotrichosis (Sporotherix schenkii)  10 of skin and cutaneous tissues  Gross: formation of single or multiple subcutaneous nodules, tend to ulcerate & discharge a small amount of thick, red-brown purulent exudate, deep ulcer & heal slowly  Mycotic diseases : Sporotrichosis Impression smear from ulcerated skin lesion in cat with sporotrichosis showing numerous cigar-shaped to oval or round budding yeast-like organisms filled with blue cytoplasm with a single round pink nucleus surrounded by a nonstaining cell wall within macrophages and extracellularly.  Mycotic diseases : Sporotrichosis  Histo: Intense pyogranulomatous dermatitis and numerous cigar- shaped to oval or round budding yeast-like organisms (pink-stained) within macrophages, scattered multinucleated giant cells & usually marked fibrosis around the granulomatous infiltrate (PAS stain)  Organisms may be intracellular following engulfment by phagocytes, or extracellular, or in the center of microabscesses  Mycotic diseases Deep mycoses  Mostly by saprophytic fungi, inhalation or skin penetration  eg. Cryptococcosis, systemic sporotrichosis  Gross: nodules, ulcers, fistulas, abscesses  Histo: granulomatous or pyogranulomatous dermatitis, panniculitis (occur as part of systemic disease) Circulatory disturbances VPM 3417: VETERINARY PATHOLOGY III