To elucidate morphologic lesion of porcine exudative epidermitis which is occurred sporadically in Korea, Staphylococcus hyicus subsp. hyicus isolated from the naturally affected pigs was inoculated to suckling pigs. The infected piglets were observed grossly and histopathologically.
Although affected piglets were taking acute, subacute, or chronic course, some piglets suffered from chronic disease showed poor prognosis and marked growth depression. Affected peglets had erythematous skin on the face, ear, and abdomen and these localized lesions appear as brownish spots of exudative epidermitis and fromed crust in the early stage. But, after this stage, the skin were covered by viscous greasy exudate and formed blackish brown crust and appeared fissures and hypertrophy.
Grossly, there has been hemorrhage with the removal of crust-like materials of epidermis and edematous subcutis. The superficial lymph nodes were edematous and swollen or congested and hemorrhagic. Some piglets had swollen ureters, cysts in the renal cortex, or polyarthritis. A few cases had mild edematous swelling of kidney, intestinal catarrh and congestion of brain.
Microscopically, skin lesions had detachment of keralinized layer and parakeratosis of epidermis, hydropic degeneration of epidermal cell, and retrogressive degeneration of hair root sheath. Dermis had edema, and infiltration of neutrophils and mononuclear cells. As the disease was proceeded, there was marked perivasculitis with lots of mononuclear inflammatory cells. More chronic lesions formed granuloma-like bodies(nodules) due to more mononuclear, perivascular inflammatory cell infiltration and proliferation of fibroblast. Lots of plasma cells and eosinophils were also present in dermis. Epidermis was hyperplastic by proliferation of basal cells stratum germinativum and epidermal pegs often extended into the dermis. In secondary infection, lots of neutrophils could be seen in epidermis and derms. Kidney had neutrophilic infiltration, necrotic and cystic glomeuuli, and dilation of renal tubules and ureters. Purulent arthritis was sometimes observed in joints.
Three days old mice administrated Staphylococcus hyicus subsp hyicus subcutaneously before had focal congestion and hemorrhage, necrosis, and subcutaneous edema of the skin. This observation was also seen in the study of mice administrated exfoliatin toxin of Staphylococcus which evoked human staphylococcal scalded skin syndrome.
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