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InFocus

Canine eosinophilic furunculosis

Canine eosinophilic furunculosis is a disease predominantly affecting the nasal area and occasionally elsewhere. It has an acute onset and is highly responsive to glucocorticoids (Miller et al., 2013). Although the exact aetiology of the condition is uncertain, it is thought that arthropod or insect bites are most likely incriminated in many cases.

Clinical features

  • Sudden onset.
  • Young dogs predisposed, possibly due to inquisitive behaviour.
  • Nodules, papules, crusts, ulceration and haemorrhage (Paterson, 2008) are all possible and depend on how rapidly veterinary advice is sought.
  • Lesions are painful, but not normally pruritic.
  • Typically affected areas include the bridge of the nose, muzzle, pinnae and periocular skin (Figures 1, 2 and 3).
  • In rare cases, the ventral abdomen, chest and pinnae are involved (Paterson, 2008).
  • Lesions are normally sterile with secondary bacterial infection uncommon, but more likely if veterinary advice is delayed.
FIGURE 1 Acute nasal lesions in a two-year-old Jack Russell terrier
FIGURE 2 Nasal lesions in a young Shih Tzu dog (courtesy of Anita Patel)

Differential diagnosis

(from Miller et al., 2013; Paterson, 2008)

  • Staphylococcal nasal folliculitis.
  • Dermatophytosis – especially to Trichophyton mentagrophytes, T. mentagrophytes var erinacei.
  • Burns.
  • Nasal solar dermatitis.
  • Drug eruptions.
  • Autoimmune disease-pemphigus foliaceus, discoid lupus erythematosus.

Diagnosis

  • History and physical examination.
  • Rule-out of differentials.
  • Cytological examination of impression smears. This is the most useful diagnostic test. Numerous eosinophils are usually present. In the later stages, there may be some degenerate neutrophils with intracellular bacteria representing secondary infection.
  • Histopathological examination. An eosinophilic infiltrative mural folliculitis and furunculosis are usually observed. There may be a mixed inflammatory infiltrate with dermal haemorrhage and collagen degeneration (Paterson, 2008). Marked dermal and subcutaneous mucinosis, and ulceration and flame figures are often noted (Miller et al., 2013).
FIGURE 3 Pinnal lesions in the young Shih Tzu (courtesy of Anita Patel)

Clinical management

  • Systemic glucocorticoids are very effective for therapy and induce a rapid response. Topical glucocorticoid therapy, although undoubtedly potentially effective, suffers from the fact that the lesions are painful, and therapy may therefore be resented.
  • Prednisolone (1-2mg/kg every 24 hours) is administered until a response is noted (usually seven to 10 days), then the same dose is given every other day for a further seven to 10 days (Miller et al., 2013).
  • Antibacterial therapy is only needed when secondary infection is detected by cytological examination and confirmed on culture. A three- to four-week course of antimicrobials effective against Staphylococcus pseudintermedius is recommended in these cases.
  • The prognosis is excellent (Figure 4).
FIGURE 4 Improvement in the same dog as Figures 2 and 3 following a 10-day course of prednisolone (courtesy of Anita Patel)

References

Miller, W. H., Griffin, C. E. and Campbell, K. L.

2013

Muller and Kirk’s Small Animal Dermatology, 7th ed., pp. 418-419.

Paterson, S.

2008

Manual of Skin Diseases of the Dog and Cat, 2nd ed., pp. 185-186.

David Grant

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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