Histoplasmosis: Epidemiology

      • Histoplasma capsulatum
      o Worldwide distribution
      o Most prevalent: Missouri, Ohio, Mississippi River Valleys
      o Most commonly diagnosed human systemic mycosis
      o Sporulation enhanced in presence of bird and bat guano
      o Very environmentally resistant
      o Contaminated soil present >15 years after removal
      • Infection
      o Inhalational
      o Ingestion
      o (Disrupted skin)
      • Pathophysiology
     o Phagocytosis: RE system
     o Dissemination or pulmonary disease?
      o Lymphatics/hematogenously
      • Clinical presentation
      o Dogs
      ¢ <4 years of age
      ¢ Gender variable
      ¢ Pointers? Brittany spaniels?
      o Cats
      ¢ 2nd most commonly diagnosed
      ¢ Gender variable
      ¢ Persians
      • Clinical presentation
      • Pulmonary
      • Acute: uncommon (contrast to human)
      • Chronic: canine
      • Disseminated
      o Chronic Pulmonary
      ¢ Mild cough
      ¢ Weight loss/inappetance
      ¢ Hilar lymphadenopathy

      o Disseminated : feline
      ¢ GI NOT common
      ¢ Bony lesions (lysis)
      ¢ Weight loss
      ¢ Fever
      ¢ Lymphadenopathy
      ¢ Pulmonary: miliary interstitial, not lymphadenopathy
      ¢ Chorioretinitis
      ¢ Hepatic/icterus
      • Diagnosis
      o Travel history (not necc recent)
      o Demonstration of organism
      o 2-4 um
      o Shrinkage of capsule
      o Intracellular (or free)
      o Lymph node aspirate CBC Bone marrow Rectal scraping (dogs)
      o Diagnosis
      ¢ Serology (CF): false negatives and positives
      ¢ 9 of 11 negative in dogs