Staphylococcus hyicus

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