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Canine impetigo in puppies

How to diagnose and manage the condition commonly seen in puppies prior to puberty

14 September 2018, at 1:57pm
FIGURE 1 Interfollicular pustular lesions of sparsely haired regions are a clinical feature of the condition in puppies
FIGURE 1 Interfollicular pustular lesions of sparsely haired regions are a clinical feature of the condition in puppies

© Didier Carlotti

Canine impetigo is a common problem in young prepubescent dogs that have been kept in poor, unhygienic conditions. It is a non-follicular subcorneal pustular condition caused by coagulase-positive staphylococci. Bullous impetigo refers to a different condition seen in old dogs with debilitating or hormonal diseases such as hypothyroidism or hyperadrenocorticism.

Clinical features

Lesions are pustules (Figure 1), papules, epidermal collarettes and crusts (Figure 2), which are seen in sparsely haired regions such as the axillae and inguinal region, and especially in the non-haired (glabrous) region of the ventral abdomen. It typically affects puppies between three and six months old and occasionally older.

Canine impetigo is non-contagious, unlike impetigo in humans. The condition is relatively benign providing that underlying factors are eliminated with prompt treatment of the lesions. Spontaneous resolution is also possible with improvement in management alone.

FIGURE 2 Pustules, papules and crusts of the glabrous skin of the ventral abdomen can be seen in a nine-week-old Dalmatian puppy. The lesions were detected at first vaccination. The puppy had been bred in poor conditions, was inadequately fed, had a worm burden and Cheyletiella infestation
FIGURE 2 Pustules, papules and crusts of the glabrous skin of the ventral abdomen can be seen in a nine-week-old Dalmatian puppy. The lesions were detected at first vaccination. The puppy had been bred in poor conditions, was inadequately fed, had a worm burden and Cheyletiella infestation

Underlying factors include:

  • Internal and external parasitism (Figure 2)
  • Viral infection such as canine distemper. Impetigo used to be a common manifestation of canine distemper, a disease which is now uncommon in the UK
  • A dirty environment, for example, in poorly managed pet shops with overcrowding, puppies originating from puppy farms and those bred in poor conditions and imported from outside the UK

Differential diagnosis

  • Demodicosis
  • Superficial folliculitis
  • Dermatophytosis
  • Early scabies – consider if pruritus is present and there has been no acaricidal treatment
  • Pemphigus foliaceus (this is possible but more likely as a differential diagnosis of bullous impetigo in old dogs)

Diagnosis

  1. History. Look for poor husbandry, absence of prior parasitic treatment, evidence of inadequate diet or a history of living in a known poor environment
  2. Physical examination. Look for interfollicular lesions that do not involve the follicles. Folliculitis will involve pustules from which a hair may be seen protruding. An examination with a hand lens and good lighting is advised, as the distinction between follicular and non-follicular lesions is important. Folliculitis cases are more difficult to resolve
  3. Cytological examination. This may be performed by pricking a pustule and smearing the contents, or by tape stripping of superficial lesions. Diff-Quik staining will demonstrate degenerate neutrophils and intracytoplasmic and extracellular cocci
  4. Culture and sensitivity testing. This has traditionally not been performed commonly in these cases. It is never unjustified, however, and is advised if simple therapeutic measures do not result in a prompt response
  5. Histopathological examination. This is rarely performed in the routine case. The subcorneal nature of the pustules will be clearly outlined, and a biopsy may be useful if doubt exists of the diagnosis, or if there is a poor initial response to treatment

Clinical management

Attention to the underlying factors described above may be all that is necessary to achieve a satisfactory response. However, treatment will facilitate a more rapid resolution. Cases may be detected at the time of first vaccination, and a useful therapeutic aim will be to achieve resolution of the lesions before the second vaccination.

Shampooing with antibacterial shampoos containing chlorhexidine (with or without miconazole) or ethyl lactate should be undertaken three times a week. A good response to topical therapy should be expected within two weeks. In cases failing to respond in this timeframe, culture and sensitivity testing should be followed by three weeks of appropriate antibacterial therapy. This is rarely necessary and should be considered only if topical therapy is ineffective.

SUGGESTED READING

Miller, W. H., Griffin, C. and Campbell, K. (2013) Small Animal Dermatology, 7th ed. Elsevier, St Louis.

David Grant, MBE, BVetMed, CertSAD, FRCVS, graduated from the RVC in 1968 and received his FRCVS in 1978. David was hospital director at RSPCA Harmsworth for 25 years and now writes and lectures internationally, mainly in dermatology.

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