Staphylococcus hyicus

Also known as: Exudative Epidermitis - Greasy pig disease

Introduction

Exudative epidermitis is a worldwide disease of pigs under 3 months of age caused by Staphylococcus hyicus. Infections are generally sporadic and can cause noticeable losses in non-immune herds.

Staphylococcus hyicus is highly contagious and persists in the environment for long periods of time, making control and prevention difficult. S.hyicus works by producing an exfoliative toxin that causes separation of cells in stratum spinosum resulting in rapid intraepidermal spread of organisms. In piglets, morbidity can range from 20 - 100% and mortality can reach 90%. Older pigs can also be infected but only mild clinical signs will occur.

The disease is usually brought into the herd and then passed on to non-immune sows, whose litters will then develop the disease. S.hyicus is found on the nasal and vaginal mucosa and from the skin of the ears and snout in healthy animals. It is spread by transmission into skin abrasions, such as that caused by mites, rough bedding or bite wounds and is predisposed to if the piglet is weak or has had a failure of passive transfer.

Clinical Signs

Its presentation is very similar to “scalded skin syndrome” in human neonates, due to skin infection by exfoliative toxin-producing Staphylococcus aureus. There are three different syndromes that occur with the exudative epidermitis disease:

Peracute - greasy, brown exudate on face, esp. behind ears, vesicopustular eruptions esp. coronets; epidermal splitting; becomes generalised over back and abdomen with the exudate causing matting of the hair. There is no pruritus. Systemic signs such as depression, fever, anorexia and possible septicaemia will then ensue and death will usually occur within 3-5 days.

Acute - signs as for the peracute disease but also skin thickening and crusting; death 4-8 days.

Subacute - lesions on the head and ears and may also involve the limbs; pigs may recover spontaneously but usually are stunted.

In adult pigs, mild skin lesions can develop, but no severe signs or systemic effects will occur.

Diagnosis

Clinical signs and the age of the pig usually are enough to make a presumptive diagnosis.

Differential diagnoses include 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) and dermatophytosis (most commonly Microsporum nanum).

Post mortem finding will show a thickened epidermis and scaling and when examined microscopically one will see subcorneal pustular dermatitis extending to hair follicles leading to superficial suppurative folliculitis. Also in later stages of the disease, hyperplastic epidermis, thick keratin crusts with cocci and microabscesses may be observed.

Bacteriological samples can be taken from the skin lesions and sent to a laboratory for isolation of S. hyicus from these lesions.

Treatment and Control

If caught early, the disease can be treated with antibiotics, such as fluoroquinolone, ampicillin, amoxycillin, ceftiofur and sulphonamides. Treatment must be carried out for at least 5 days and there is no guarantee that piglets will return to full health, with some remaining stunted for life.

Rehydration solutions and electrolytes are necessary and piglets should be washed in a mild disinfectant solution such as cetrimide. Disinfection of all farrowing crates and pens and other housing should be performed to try to eliminate the risk of further outbreaks.

Prevention measures include clipping of teeth in neonates, providing soft bedding and treatment for mites. Sows should be washed before entering the farrowing crates and all areas should be disinfected thoroughly before sow or litter are placed in there.

References

Cowart, R.P. and Casteel, S.W. (2001) An Outline of Swine diseases: a handbook Wiley-Blackwell
Jackson, G.G. and Cockcroft, P.D. (2007) Handbook of Pig Medicine Saunders Elsevier
Straw, B.E. and Taylor, D.J. (2006) Disease of Swine Wiley-Blackwell
Taylor, D.J. (2006) Pig Diseases (Eighth edition) St Edmunsdbury Press ltd