Exudative epidermitis by Staphylococcus hyicus producing ExhC: control proposals against an emergent pathogen in intensive pig production

Abstract

Exudative epidermitis (EE) is an occasional infectious disease affecting suckling and weaned piglets, with severe presentation in outbreaks. We described the diagnosis and control measurements conducted after an outbreak of EE caused by Staphylococcus hyicus producing an exfoliative toxin type C (ExhC) in a commercial 4,000-head sow farm. Clinical disease was observed in suckling piglets, with a 70% of morbidity, and a significant increase of mortality rate of 5% during this period (p < 0.0001) was detected. The bacteria could be recovered from skin and internal organs of affected animals, and the pulsed-field gel electrophoresis (PFGE) analysis showed that all the isolates were genetically indistinguishable, suggesting a common origin. Certain deficiencies in the cleaning and disinfection protocols carried out in the farrowing unit could be responsible for the severity of the outbreak. The efficacy of autogenous vaccination in sows with an inactivated vaccine based on complete ExhC-positive S. hyicus isolates at five and two weeks before farrowing in combination with the improvement of managements measures and selection of healthy animals for replacement allowed the resolution of the outbreak, completely reducing the morbidity and mortality rates after three months. The importance of an adequate diagnosis, biosecurity evaluation and the use of appropriate immune prophylaxis based on autogenous vaccines, are essential tools for the rapid and effective resolution of disease outbreaks of EE.