Congenital/Environmental/Infectious

• Congenital Hypotrichosis

  Absence of hair follicles or abnormal follicular development
• Congenital Hypotrichosis in domestic species

  • Cattle
  • Dogs
  • Cats
• Congenital Hypotrichosis in Cattle

  • Hereditary vs acquired (BVD, iodine, pituitary hypoplasia, teratogens)
  • Rule out telogen or anagen defluxion
• Hereditary Collagen Dysplasia

  Distensible skin which tears easily
• Ichthyosis

  Fish scales
• Environmental Induced Skin Disease

  • Actinic (Sun) Injury
  • Chemical Injury
  • Physical Injury
• Actinic (Sun) Injury

  • Amount of light reaching skin depends on environmental factors (atmosphere, latitude, altitude, shelter) and host factors (hair, pigmentation, stratum corneum, genetics)
  • Visible light vs UV-A vs UV-B vs UV-C
  • Generates free radicals that damage nucleic acids, proteins and lipids
  • Causes mutagenesis through pyrimidine dimer formation in P53 gene
• Primary Phototoxicity (Sunburn)

  Direct endothelial damage and damage to keratinocytes with release of inflammatory mediators
• Photosensitization

  Photodynamic substances in skin are activated by UV-A or visible light
• Types of Photosensitization

  • Type I - exogenous origin of photodynamic agents
  • Type II - aberrant endogenous pigment synthesis
  • Type III - failure to remove phylloerythrin (hepatogenous type)
  • Type IV - idiopathic
• Chemical Injury

  Agent must penetrate hair and stratum corneum, enhanced by moisture and/or damage
• Chemical Injuries

  • Primary Contact Irritant Dermatitis
  • Gangrenous Ergotism
  • Fescue Toxicosis
  • Thallium, Selenium, Mercury, Arsenic
• Physical Injury

  Acral Lick Dermatitis, Callus/Hygroma, Abrasion/Laceration/Ulceration/Foreign Bodies, Radiation, Extremes in Temperature
• Types of Infectious Skin Disease

  • Viral
  • Bacterial
  • Mycotic
  • Parasitic
  • Algal
  • Protozoal
• Viral Skin Diseases

  • Local infection requires abrasion or arthropod bite
  • Systemic viral infection can be epitheliotropic or pantropic
• Viral Skin Diseases

  • Contagious Viral Pustular Dermatitis (Orf)
  • Canine Distemper
  • Scrapie
  • Vesicular Exanthema
• Diagnosis of Viral Dermatitides

  • History and clinical signs/lesions
  • Skin biopsy
  • Serology
  • Virus isolation or identification
• Bacterial Skin Diseases (Pyodermas)

  • Result depends on agent pathogenicity and host defence mechanisms
  • Healthy skin is resistant due to lack of moisture, continuous desquamation, and ecological pressure of normal flora
  • Factors assisting bacterial colonization include moisture, dirt, altered cornification, and physical damage
• Types of Bacterial Skin Diseases

  • Primary (one species, characteristic pattern, successful antibiotics, no scarring, short duration, no lymph node/systemic involvement)
  • Secondary (multiple species, not characteristic, unsuccessful antibiotics, scarring, chronic, lymph node/systemic involvement)
• Diagnosis of Bacterial Skin Diseases

  • History and lesions
  • Culture
  • Skin biopsy
• Bacterial Skin Diseases

  • Pyotraumatic Dermatitis (Hot Spots)
  • Puppy Pyoderma
  • Skin Fold Pyoderma
  • Subcutaneous Abscesses
  • Papillomatous Digital Dermatitis
  • Dermatophilosis
  • Exudative Epidermitis (Greasy Pig Disease)
  • Diamond Skin Disease
  • Septicemia
• Types of Mycotic Skin Diseases

  • Superficial Mycoses (Dermatophytosis, Dermatomycosis)
  • Subcutaneous Mycoses
  • Systemic Mycoses
• Dermatophytosis (Ringworm)


  Common, contagious, attacks keratinized layers, causes inflammation due to proteases
• Dermatomycosis

  Fungal infection of skin, hair or claws caused by a non-dermatophyte, e.g. Malasseziasis, Candidiasis
• Ringworm is the most commonly reported zoonosis in people working with cattle, and about 50% of people exposed to infected cats develop lesions
• Subcutaneous Mycoses involve traumatic implantation of saprophytic fungi
• Systemic Mycoses are usually due to compromised resistance and occur primarily by inhalation, e.g. Blastomycosis, Cryptococcosis