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German Shepherd dog pyoderma

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01 March 2016, at 12:00am

David Grant continues his series looking at dermatological conditions.

GSD PYODERMA IS CLASSIFIED AS A DEEP PYODERMA with furunculosis and cellulitis frequently observed. Although there are many underlying causes for deep pyodermas, in general the problem in 

German shepherd dogs is often idiopathic with a guarded outlook for cure. Many such cases require life-long therapy and euthanasia may be requested by the owner in severe cases. 

Cause

  • Staphylococcus pseudintermedius is considered to be the primary pathogen.
  • Other bacteria such as E. coli, Proteus and Pseudomonas can aggravate the clinical picture due to opportunistic infection.
  • Underlying allergic diseases to be considered include atopy, flea- bite hypersensitivity, and food hypersensitivity.
  • Underlying endocrine disorders, of which hyperadrenocorticism and hypothyroidism are the most important.
  • Parasitic infestation particularly Demodex canis and also fleas and Sarcoptes scabiei.

  • It is considered to be a familial immunologically mediated deep pyoderma in German shepherd dogs (Miller, Grif n and Campbell, 2013).
  • Studies have shown that affected dogs have an increased number of CD8+ and decreased numbers of CD4+ and CD21+ lymphocytes in their circulation. Immunopathological studies of skin biopsies have also demonstrated markedly fewer T lymphocytes in affected dogs. 

Clinical signs

  • Signs of German shepherd pyoderma are usually very severe and require intensive investigation and treatment. 
  • Lesions more typical of superficial pyoderma may exist initially. These consist of papules, pustules, epidermal collarettes and crusts. They may easily be missed in the early stages due to the thick coat. 
  • Later, and often quite quickly, the lesions progress to deep folliculitis/furunculosis, with exudation, a serosanguinous discharge and ulceration. These lesions can be quite extensive and demonstrable by clipping as in the figure. This dog had also lost weight and was systemically unwell. 

Diagnosis

  • The presence of blood and pus clearly identifiable on visual examination and made more obvious by squeezing the skin. There may be extensive crusting and ulceration. 
  • Cytology. There is a severe pyogranulomatous inflammation with many toxic neutrophils. Bacteria (cocci, and in severe cases rods) may be seen.
  • Skin scrapings for parasites. 
  • Biopsy. This may identify Demodex in cases of chronic cases where lichenification has made positive identification from skin scrapings difficult. 
  • Bacterial culture. This is essential in all cases as appropriate antibacterial therapy needs to be identified by antibacterial sensitivity testing.
  • A determined effort should be made to identify possible underlying factors. 
  • Routine haematology and biochemistry.
  • Dynamic function tests for hyperadrenocorticism.
  • Thyroid function tests. 
  • Allergy investigation to include food trials and possible allergy testing (intradermal testing or serology). These tests are best considered in those cases where remission has been obtained, though not maintained, and where the history, physical examination, and rule out of other causes suggests atopy and in addition immunomodulatory treatment has been discussed and agreed with the owner. 

Treatment

  • Identify underlying causes and treat them. Also ensure that parasite control is comprehensive. 
  • Systemic antibacterial treatment with antibiotics effective for Staphylococcus pseudintermedius, as identified from sensitivity testing, at the correct manufacturer’s dose and until remission from clinical signs with an additional two weeks. This may involve several months or more.
  • Topical therapy during this time with antibacterial shampoos such as chlorhexidine/miconazole (Malaseb, Dechra) and with whirlpool baths.
  • Topical therapy alone may help in preventing a relapse in recurrent cases 

Prognosis 

  • The clinical course is variable. Affected dogs have deep skin infections that resolve slowly and recur frequently. Either there is no definable cause of the infection or if one is defined, flea infestation for example, the severity of the infection is well out of proportion to the stimulus (Miller, Grif n and Campbell, 2013).
  • Where an underlying cause is found and treated aggressively, remission can be obtained and with treatment of the underlying cause recurrence prevented.
  • In other cases there is either a poor response to treatment or the problem recurs frequently.
  • For these frustrating cases life-long control is required, which may be difficult, often leading to requests for euthanasia. Many of these cases may be assumed to have a cell-mediated immune deficiency (Miller, W. H., 1991). 

References and further reading 

  1. Miller, W. H. (1991) Deep pyoderma in two German shepherd dogs associated with a cell mediated immunodeficiency. J Am Anim Hosp Assoc 27: 513. 
  2.  Miller, W. H., Grif n, C. G. and Campbell, K. L. (2003) In: Muller and Kirk’s Small Animal Dermatology, 7th edition, pp203-205. 
  3. Elsevier. Paterson, S. (2008) In: Manual of skin diseases of the dog and cat, 2nd edition, pp44-45. Blackwell Publishing.