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Histoplasmosis

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

Diagnosis

History
Clinical signs
Physical exam
Radiography
Lab tests

Treatment

Name	Summary
Supportive care	Isolate 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 B	1 mg/kg administered IT TID + 1.5 mg/kg IV	K Marx

Support

Prevention

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

Kipyegon, K. E., Musyoki, S. K., & Kariuki, S. M.. Detection of Histoplasma Capsulatum in Domestic Chicken Droppings in Olenguruone, Nakuru County. European Scientific Journal, ESJ, 13(15) (2017)
Duc Tan Nguyen, Ivana Bilic, Barbara Jaskulska, Michael Hess, Duc Quyet Le, Luc Ngoc Le Hua, Vu Vy Huynh, Sam Thi Nguyen and Hung Vu-Khac Prevalence and Genetic Characterization of Histomonas meleagridis in Chickens in Vietnam. Avian Dis (2015)
Quist, E. M., et al. Disseminated histoplasmosis with concurrent oral candidiasis in an Eclectus parrot (Eclectus roratus) Avian pathology 40.2 (2011)
Richter, Marianne, et al.. Keratitis due to Histoplasma spp. in a horse Veterinary ophthalmology 6.2 (2003)
Hoff, G. L., & Bigler, W. J. The role of bats in the propagation and spread of histoplasmosis: a review.. Journal of wildlife diseases, 17(2), 191-196. (1981)
Ajello, Libbero. Geographic distribution of Histoplasma capsulatum Mycoses 1.5 (1958)

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

Avian tuberculosis