Small Animal Dermatology, 3rd edition

CHAPTER 36 NOCARDIOSIS AND ACTINOMYCOSIS 537

Bite wound abscesses

Draining tracts resulting from foreign bodies.

DIAGNOSTICS

 Nocardiosis:
Neutrophilic leukocytosis
Nonregenerative anemia with long-standing infections (anemia of chronic

disease)

Chemistries: usually normal; hypergammaglobulinemia may be seen with long-

standing infections; hypercalcemia with renal dysfunction

Radiographs: may reveal pleural or peritoneal effusion, pleuropneumonia, or

osteomyelitis

Cytology: fine-needle aspirate; thoracentesis or abdominocentesis for samples;

stain these or other exudates with Romanowsky, Gram or Brown-Brenn, and

modified acid-fast stains for rapid diagnosis; may reveal gram-positive branching

filamentous rods and cocci

Tissue culture: diagnostic; aerobic culturing on Sabouraud medium

Tissue PCR testing of 16S ribosomal DNA to permit speciation: assists in selec-

tion of antimicrobial therapy

N. asteroides:more suppurative pyogranulomatous reaction than withActino-

mycesspp.

N. brasiliensis:granulomatous reaction with extensive fibrosis

Histopathology: nodular to diffuse dermatitis; panniculitis; with or without tis-

sue grains

Although the organism is usually present, it cannot be distinguished in cytology

or histopathologically fromActinomycesspp.

Hypercalcemia may be present and impair renal function.

 Actinomycosis:
Tissue culture; anaerobic culture may take several weeks
Histopathology: nodular to diffuse pyogranulomatous dermatitis and panni-

culitis

Sulfur granules noted in approximately 50% of cases

Stain with Gram, Brown-Brenn, or Gomori methanamine silver.

THERAPEUTICS

 Pleural or peritoneal effusions and disseminated form: inpatient until clinically stable

and effusion removed; fluid therapy for rehydration and maintenance often needed.

 Long-term antibiotic therapy and draining fistulous tracts: outpatient.

 Diet: encourage consumption by offering foods with appealing tastes and smells;

forced enteral feeding for anorectic inpatients essential; orogastric tube feeding

preferred.