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Histoplasmosis is an infectious, but non-contagious fungal disease caused by Histoplasma capsulatum. It has reported commonly in birds at zoos, and occasionally in chickens and turkeys. The disease occurs worldwide, however it has been found to be indigenous in areas in the United States bordering the Missouri, Ohio, and Mississippi rivers.

Chickens become infected by inhaling dust containing H. capsulatum spores. In many cases, birds are concurrently infected with other fungi, usually Aspergillus spp. and have recently undergone some sort of stressful event.

The disease is diagnosed based on three criteria: culture of the organism, histopathology, and histoplasmin sensitivity. The characteristic histopathology is histiocytic to granulomatous inflammation with intracytoplasmic narrow-based budding yeasts measuring 2–4 µm in diameter.

Clinical Signs

Weight loss
Chronic respiratory signs
Loss of appetite


  • History
  • Clinical signs
  • Physical exam
  • Radiography
  • Lab tests


Supportive careIsolate the bird from the flock and place in a safe, comfortable, warm location (your own chicken "intensive care unit") with easy access to water and food. Limit stress. Call your veterinarian.
Amphotericin B1 mg/kg administered IT TID + 1.5 mg/kg IVK Marx



  • Decrease exposure to soil mixed with accumulation of feces from birds or bats.
  • Spraying infected soil and feces with 3% formalin destroys some spores.
  • Do not overcrowd or stress birds
  • Execute good management practices

Scientific References

Risk Factors

  • Birds living in warm, humid regions
  • Poor sanitary practices, allowing accumulation of feces in soil.
  • Presence of bats
  • Overcrowding
  • Recent stressful event (introduction to a new flock of birds, excessive bullying or fighting among flock members, exposure to extreme heat or cold, poor living conditions, overcrowded conditions, lack of resources such as feed or water, rough handling, predator attack or predator stalking, recent injury or sickness, etc.)

Also Consider