Canis ISSN: 2398-2942

Nocardiosis

Contributor(s): Stephen Barr, Alexander German, Danielle Gunn-Moore, Kim Willoughby

Introduction

  • Uncommon bacterial disease of dogs.
  • Cause: infection with Nocardia spp Nocardia spp (usually Nocardia asteroides, occasionallyN. brasiliensis and N. otitidis-caviarum).
  • Signs: vague signs of illness, dyspnea.
  • Diagnosis: pyogranulomatous lesions detected, bacterial culture.
  • Treatment: surgical drainage (or excision), antibiotic therapy.
  • Prognosis: variable to poor (depending on underlying cause).

Pathogenesis

Predisposing factors

General

  • Opportunistic infections in most cases.
  • Immunosuppressed individuals (particularly cell-mediated immunity) are at particular risk.
  • Immunosuppressive drug therapy.
  • Concurrent disease, eg pulmonary disease, metabolic disease (diabetes mellitus Diabetes mellitus , hyperadrenocorticism Hyperadrenocorticism ), neoplasia, immunologic disease, etc.

Pathophysiology

  • Organism is a ubiquitous soil saprophyte and can survive for a long time in the environment.
  • After infection, it becomes an intracellular pathogen.
  • Three forms are recognized:
    • Pulmonary nocardiosis.
    • Systemic nocardiosis.
    • Solitary extrapulmonary nocardiosis.
  • Coinfection with canine distemper virus Canine distemper disease has been reported.
  • Inhalation of soil organisms leads to the involve lungs and contiguous structures (pleura, mediastinum, pericardium). Secondary systemic spread and dissemination may then occur. Solitary extrapulmonary lesions may also arise when the organism infects wounds.
  • Pathogenicity depends upon the strain of the organism, the infective load and host susceptibility, eg presence of immunosuppression.
  • Initial host response involves neutrophil killing then cell-mediated immunity. Virulent strains can evade host defense mechanisms by inhibiting phagosome-lysosome fusion, neutralizing phagosomal acidifcation and resisting the oxidative burst.
  • In tissues, granulomatous reactions develop with exudate occasionally containing sulfur granules.
  • Not transmissible from infected animals but other susceptible animals could potentially be infected from the same source.

Diagnosis

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Treatment

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Outcomes

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Further Reading

Publications

Refereed papers

Other sources of information

  • Edwards D F (1998) Nocardiosis. In: Infectious diseases of the Dog and Cat. 2nd Edn. Ed. Greene C E. W B Saunders Co. pp 308-312.


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