IN-DEPTH: SELECTED TOPICS IN DERMATOLOGY Equine Dermatology Stephen D. White, DVM, Diplomate ACVD; and Anthony A. Yu, DVM, MS, Diplomate ACVD Authors’ addresses: Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California at Davis, Davis, CA 95616 (White); and Department of Clinical Studies, Ontario Veterinary College, University of Guelph, Guelph, Ontario N1G 2W1, Canada (Yu); e-mails:
[email protected] (White) and
[email protected] (Yu). © 2006 AAEP. I. Diagnosis and Treatment of the Pruritic Horse Pyoderma (Bacterial Skin Infections) ative border as seen in dogs with superficial pyoderma; Figs. 1 and 2), or encrusted papules sim- Stephen D. White, DVM, Diplomate ACVD ilar to the miliary dermatitis reaction pattern in cats.6 These infections tend to be variable in their 1. Introduction intensity of pruritus. Histology usually shows fol- Bacterial folliculitis (superficial pyoderma) is usu- liculitis and/or furunculosis, but bacterial colonies ally caused by a coagulase positive Staphylococcus are not always seen. A truncal form of bacterial species. Both S. aureus and S. intermedius have folliculitis (contagious acne, contagious pustular been isolated.1,2 In one study, S. aureus accounted dermatitis, or Canadian horsepox) is often associ- for twice as many isolates as S intermedius; the ated with poor grooming, trauma from tack and same study isolated some strains of S. hyicus as saddle, warm wet weather, and heavy work. It is well.3 Interestingly, in another study, lysozymes painful and interferes with working and riding. from equine neutrophils were only slightly bacteri- It is usually caused by a coagulase positive Staphy- cidal for S.