Exudative epidermitis

In suckling piglets, reddened skin is often first seen in the armpits and groin. It turns scaly, then oozes serum, and within 24 to 48 hours a moist, greasy exudate and brown-black crusts can cover the whole body. Affected pigs become listless, depressed and stop eating. Lesions may instead form thick crusts in discrete, circumscribed patches. Severe outbreaks bring progressive dehydration and wasting, and young piglets can die within a day.

Exudative epidermitis, or greasy pig disease, is caused chiefly by virulent strains of Staphylococcus hyicus; Staphylococcus aureus, including methicillin-resistant strains, can join the infection. The disease is driven by exfoliative toxins, six of which are known (ExhA, ExhB, ExhC, ExhD, SHETA and SHETB). These toxins are serine proteases that cleave desmoglein-1, the protein holding keratinocytes together, so cells separate in the stratum spinosum and the skin blisters and peels. Sebaceous exudation follows, then erosions and crusts. Histology shows purulent dermatitis with masses of coccoid bacteria, neutrophil microabscesses, hyperkeratosis and erosion or ulceration. Widespread skin damage leads to fluid loss, dehydration and wasting.

The disease affects pigs, most severely piglets aged about 3 to 32 days, both suckling and recently weaned, and occurs up to around six weeks of age. Sows carry the organism, and it passes to piglets from these carriers and by direct contact with infected skin. Risk rises with skin trauma, concurrent viral disease, nutritional deficiencies, dermatophytosis, poor hygiene, poor ventilation, high humidity and genetic predisposition; mycotoxin-contaminated feed was a factor in one reported outbreak. Morbidity can reach 90 per cent. S. hyicus also infects horses, goats and cattle and is considered a zoonotic risk, and methicillin-resistant staphylococci from affected herds raise concern for farm workers. Antimicrobial resistance in S. hyicus is widespread.

Skin (epidermis, stratum spinosum, sebaceous glands), whole body surface, fluid and electrolyte balance

Strict hygiene with hot water, detergents and disinfection; mycotoxin-safe feed; topical chlorhexidine washing; autogenous herd vaccines given to sows, which in one herd roughly halved mortality from the disease in their weaned pigs.

Young piglets can die within 24 hours from anorexia and dehydration; mortality is high in severe outbreaks. Treatment that ignores susceptibility testing may fail because multidrug resistance is common; guided therapy plus hygiene resolved one outbreak.