Canine pyodermas are purulent infections of the skin. There are three classifications of canine pyoderma – surface, superficial and deep.
Surface pyoderma is a very common condition in small animal practice. A survey of 100 small animal vets found that 7% of all dogs seen in the summer exhibited surface pyoderma.1
In surface pyoderma, infection is confined to the interfollicular epidermal layers of the skin meaning that topical therapies are usually the most appropriate treatment choice. Canine pyoderma is generally associated with staphylococcal infection, principally S. pseudintermedius.
The most common forms of surface pyoderma are pyotraumatic dermatitis (also known as acute moist dermatitis, wet eczema or hot spots) and intertrigo (skin fold dermatitis).
1. Modus Market Research Report (2007)
The root cause of pyotraumatic dermatitis is unclear but it frequently involves opportunistic infection of the skin following a self inflicted trauma which impairs the barrier function of the skin. Triggers for self-trauma in dogs include atopic dermatitis, food hypersensitivity, flea allergy dermatitis, other ectoparasites, otitis externa or pain that causes a dog to chew, lick or scratch the skin.
Intertrigo develops as a result of friction between two skin surfaces. The condition is common in breeds with prominent skin folds and in obese dogs, which can develop additional skin folds. Microbial overgrowth in these areas is also increased when there is poor air ventilation and/or trapped moisture (skin secretions, tears, saliva or urine).
Hormonal disorders can also contribute to the proliferation of infectious organisms as they affect the immune mechanisms of the skin.
Lesions are typically erythematous, pruritic and exudative. Depending on the location they may be covered by matted fur.
Diagnosis of surface pyoderma is based on a review of the clinical signs and medical history. Cytology, bacterial culture and antibiotic sensitivity testing may also be considered. If an underlying allergic skin disease is suspected, then further tests/investigations may be performed to determine the dog’s specific allergies. Blood tests to establish if the dog has an endocrine disease such as hypothyroidism or hyperadrenocorticism (Cushing’s syndrome) may also be warranted if there are other clinical signs that suggest these may be the root cause of the problem.
For pyotraumatic dermatitis, clipping of the hair and washing of the affected areas are essential to increase skin ventilation, remove infectious debris and enable further assessment. In some cases, this will be sufficient to stop self-trauma and enable healing, although most cases require additional antimicrobial and anti-pruritic treatment. It is also important to address any underlying cause that has been detected.
The most effective way of treating intertrigo is removal or reduction of affected skin folds. Weight reduction can be an answer in some cases, but surgery may be necessary for severe, relapsing cases.
Clipping of the hair in skin fold infections is indicated in long-haired breeds to remove matted fur that traps debris to the skin surface and impairs ventilation. However, in short-coated breeds clipping can cause stubble that traumatises the skin on the opposing side of the fold, causing further irritation.
As in pyotraumatic dermatitis, cleaning of the skin is essential and topical antimicrobial products can be used for treatment of bacterial infection. Yeast infection with Malassezia pachydermatis is also frequently seen in intertrigo, either alone or in combination with bacterial infection, and for these cases preparations with antifungal efficacy should be selected.