Staphylococcus hyicus

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Exudative epidermitis (Greasy pig disease)

  • Worldwide disease of pigs under 3 months of age caused by S. hyicus
  • Highly contagious and persists in the environment for long periods
  • S. hyicus produces exfoliative toxin that causes separation of cells in stratum spinosum resulting in rapid intraepidermal spread of organisms
  • Similar to “scalded skin syndrome” in human neonates, due to skin infection by exfoliative toxin-producing Staphylococcus aureus
  • Excessive sebacious secretion and exudation on surface of skin
  • Pigs are anorexic, febrile, depressed and have a greasy, non-pruritic dermatitis
  • SKin thickened, wrinkled and scaley
  • Acute death in piglets under 3 weeks due to dehydration and septicaemia
  • 20-100% morbidity; up to 90% mortality
  • Organism enters skin via abrasions e.g. bite wounds
  • Carried in vaginal mucosa and skin of sows
  • Predisposed by lack of milk, weaning and other infections
  • Piglets from non-immune sows are predisposed
  • Passive transfer of antibodies from immune sows and development of immunity with age protect against disease
  • Isolation from skin lesions
  • Early systemic antibiotics amd topical antiseptics/antibiotics useful
  • Disinfection after outbreak
  • Wash sows before farrowing
  • Differential diagnosis:
    • Mange (Sarcoptes scabiei var. suis)
    • Swine parakeratosis (zinc and essential fatty acid deficiency)
    • Porcine juvenile pustular psoriasiform dermatitis (collarettes or rings typically on the ventrum of young pigs)
    • Dermatosis vegetans (associated with a giant cell pneumonia)
    • Dermatophytosis (most commonly Microsporum nanum)

Pathology

  • = Exudative epidermitis of pigs
  • Caused by Staphylococcus hyicus
  • Affects neonatal piglets - often fatal, older piglets - milder disease
  • Focal erosion of stratum corneum
  • Brown exudate
  • Dermatitis around eyes, ears, snout, chin and medial legs, may spread to ventral abdomen and thorax
  • Rapidly becomes generalised -> greasy exudate over red skin -> hardened, cracked exudate
  • In older piglets, milder localised disease develops around eyes, ears and face
  • Grossly:
    • Thickened epidermis, scaling
  • Microscopically:
    • Early - subcorneal pustular dermatitis extending to hair follicles -> superficial suppurative folliculitis
    • Late - hyperplastic epidermis, thick keratin crusts with cocci, microabscesses