Vetnews | Augustus 2025 42 « BACK TO CONTENTS Deep pyoderma isn’t just a severe superficial pyoderma. It is a distinct, complex disease process driven by a vicious cycle of inflammation and infection. The initial trigger is often inflammation caused by follicular rupture, trauma, or chronic friction, which breaks down the skin’s natural defences and allows bacteria to invade deeper tissues. Without addressing both the infection and the underlying inflammation, treatment will be prolonged, frustrating, and prone to failure, resulting in recurrence. The Inflammation-Infection Cycle: The Root of Deep Pyoderma The hallmark of deep pyoderma is the inflammatory cascade that compromises local immune defences and tissue integrity. Common initiating factors include: • Furunculosis: ruptured hair follicles spill keratin and bacteria into the dermis, triggering intense inflammation. • Traumatic impaction of hair shafts, especially in shortcoated breeds, after grooming or lying on hard surfaces (think of these short hairs as little spears poking the dermis and subcutis, causing chronic irritation). • Chronic friction or pressure points: such as over bony prominences like hocks and elbows, or interdigital skin, axillae and even the inguinal area of obese dogs. Inflammation causes tissue damage and creates a hostile environment where bacteria flourish. Secondary bacterial invasion exacerbates inflammation further, creating a self-perpetuating cycle. Why Managing Inflammation is Just as Important as Killing Bacteria Antibiotics are vital, but deep pyoderma cannot be successfully treated without targeted inflammation control. Unchecked inflammation: • Delays healing by damaging healthy tissue • Fuels further follicular rupture and furunculosis • Sustains a chronic infection-prone environment Anti-inflammatory treatment strategies include: • Topical therapies: Use of antiseptic shampoos (chlorhexidine 2–4%) and topical glucocorticoids or calcineurin inhibitors can reduce inflammation and bacterial load locally. Shampoos are important adjuncts to systemic therapy, but be careful how these dogs are washed, as grooming can cause further trauma and spread infection. • Systemic anti-inflammatories: Short courses of systemic corticosteroids (e.g., prednisolone 0.5–1 mg/kg/day) may be warranted in severe, painful, or highly inflamed cases to break the cycle quickly. For chronic recurring cases, Cyclosporin can be considered, but bear in mind the onset of clinical effect is 3 – 6 weeks, therefore not ideal for acute severe inflammatory lesions. Also, due to immunosuppression, culture and sensitivity, and appropriate antimicrobial therapy are essential, as cyclosporin may unmask other resistant bacteria. • In patients with comorbidities that prevent corticosteroid use, one can consider Oclacitinib (Apoquel) at the higher end of the dose range (0.6mg/kg), twice daily to reduce some of the inflammation – this is off-label use and in the author’s experience not very effective in controlling severe inflammation. • Address underlying causes: Allergies, ectoparasites, conformational friction, or other primary diseases must be identified and managed to prevent recurrence. Cytology: Your Day One Diagnostic Cornerstone Cytology in the first consultation remains indispensable to confirm infection, identify bacterial morphology, and assess inflammatory cell types. Collect samples by: • Direct impression smears from moist lesions • Swabs from draining tracts or interdigital spaces • Fine needle aspirates from nodules – if nodules are painful, topical lidocaine cream can be applied and FNA reattempted 40-60 minutes later. Deep Pyoderma in Dogs: When Infection Gets Under the Skin By Monica Burger, BSc BVSc (UP) Figure 1: classic deep pyoderma on the elbow of a large breed dog. Elbow hygromas often present with deep pyoderma due to compromised skin, furunculosis and constant traumatic impaction of hair shafts when lying on hard surfaces.
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