Week 2 PDF - Veterinary Skin Diseases

Alopecia (atrichia): absence of hair Hypotrichosis: less than the normal amount of hair. Animals with hypotrichosis are more susceptible to sunburn, temperature extremes, bacterial and fungal...

Alopecia (atrichia): absence of hair Hypotrichosis: less than the normal amount of hair. Animals with hypotrichosis are more susceptible to sunburn, temperature extremes, bacterial and fungal infections. 1 Collagen dysplasia ✓ connective tissue disorder ✓ Gross lesion: hyper- extensibility and laxity Epitheliogenesis Imperfecta (Aplasia Cutis) ▪ Results from failure of the stratified squamous epithelium of skin, adnexa, and/ or oral mucosa to develop completely 2- Environmental induced skin disease ❑Sun (Actinic) injury ❑Chemical injury ❑Physical injury  1. Sunburn and Solar Dermatosis / Dermatitis Sunburn due to: ▪ direct endothelial damage damage to keratinocytes with release of inflammatory mediators Solar dermatitis ▪ acutely see initial redness (sunburn erythema), followed by pain, ± edema, blistering, etc ▪ chronically see thickened inflamed skin +/- dysplasia / neoplasia Ventral abdomen and thorax. Solar dermatitis  2. Photosensitization Occurs when photodynamic substances in skin are activated by UV-A or visible light. Type I : exogenous origin of photodynamic agents, especially certain plant toxins and drugs Type II : aberrant endogenous Type III (hepatogenous type): failure to remove a photoreactive metabolite of chlorophyll Type IV : unknown etiology / pathogenesis Gross lesions: occur in areas with poorly pigmented hair & skin  Chemical Injury Local application : penetrate hair and stratum corneum; enhanced by the moisture and cause skin damage. Systemic absorption: ingestion of toxins with systemic effects on the skin and usually other organs ❑Physical injury ✓ Abrasion / Laceration / Ulceration / Foreign Bodies Radiation ✓ Extremes in Temperature ✓ Feline Psycogenic Dermatitis  Lick dermatitis / lick granuloma, neurodermatitis Psychogenic dermatitis Developing on an extremity Caused by persistent licking or chewing (form of repeated trauma and leads to gross and histological changes Causes: psychogenic disorders (emotional / psychological) usually results from: boredom: alone during day, Anxiety: new home, pet, baby, etc. / loss of companion, etc. / any other stress. 3- infectious skin disease ❑Viral skin diseases ❑ Bacterial skin diseases ❑Mycotic skin diseases ❑Parasitic skin diseases ❑Protozoal skin diseases  ❑Viral skin diseases Infectious agents enter the animal body via: Trauma to epidermal surface Hair follicles Ducts of glands Migrating via nerves or hematogenous route Types of viral skin diseases Local viral infection of the skin Systemic viral infection with skin involvement  1) Local viral infection of the skin Poxviruses Infect most domestic animals, wild, laboratory animals and birds. Can be specific and zoonotic Contagious Pustular Dermatitis Common / worldwide parapoxvirus infection of sheep and goats Cause significant mortality especially in young animals as a result of systemic disease Typical pox phases (vesicles / pustules / crusts) but more hyperplastic / proliferative Lesions most commonly on the lips (initiated by abrasions from pasture /forage) Contagious ecthyma, skin, lamb. Note crusts around nose and lips. the lesions are the late stage of the disease, formed after rupture of vesicles and pustules, and are responsible for the common name scabby mouth.  2) Systemic viral infection with skin involvement Viremic phase of a systemic infection Examples: Epitheliotropic viruses such as poxviruses, vesicular viruses (FMD, VS), BVD Pantropic viruses such as canine distemper, hog cholera Diagnosis: history and clinical signs / lesions. skin biopsy - mostly vesicular to pustular dermatitis, ± viral inclusion bodies. serology / virus isolation / virus identification (i.e., PCR) Foot and Mouth Disease (FMD) Canine Distemper Scrapie Scrapie has also been called mad sheep disease, and is a brain disease similar to BSE or mad cow disease. Canine: ✓ Papilloma virus ✓ Canine distemper virus Cattle: ✓ Bovine mammillitis virus ✓ Pseudocowpox ✓ Papilloma virus ✓ Horses: Papilloma virus B, Head, cow. Note multiple, irregular, alopecic, verrucous papillomas Horses: Papilloma virus Superficial Pyoderma. Erythematous dermatitis with epidermal collarettes formation is apparent. 20 Factors assisting bacterial colonization / proliferation: moisture and dirt altered cornification physical damage Result depends on agent pathogenicity / host defense mechanisms 21 1. Cutaneous (Superficial) Mycoses 22