Aspergillosis is an infectious, non-contagious fungal disease. The disease is caused by infection with species belonging to the Aspergillus
genus. Aspergillus fumigatus
is the most common species isolated from infected birds, followed by A. flavus
. Aspergillosis primarily affects the respiratory tract however it can also cause eye infections. The disease manifests in two different forms---as an acute or chronic infection.
What are the clinical signs?
- Acute form: Acute aspergillosis, also referred to as Brooder pneumonia is characterized by severe outbreaks in newly hatched chicks and is associated with high morbidity and high mortality rates.
- Chronic form: Chronic aspergillosis, is a disease that occurs sporadically in adult chickens.
Clinical signs in chicks usually start to present within 3-5 days after exposure. Affected chicks will initially show signs that they are having difficulty breathing, with an increased respiratory rate and open-mouth breathing. If chicks survive (5 to 50% usually will die the first 1-3 weeks of life), they will develop a loss of appetite, increased thirst, lethargic behavior, and extreme weakness. Some will develop eye swelling leading to blindness, ascites, or torticollis (where they are observed twisting their neck to one side). In other cases, chicks may be subclinically affected initially, showing no signs of infection, but later develop breathing problems as they increase in body weight which proportionally increases demands on the functional capacity of their lungs.
Where is the fungus found?
spp. are naturally found in small concentrations throughout the environment---in the air, soil, bedding, etc. Higher amounts of Aspergillus
spp. develop through the presence of dust and mold.
How is it spread?
Aspergillosis is not a transmissible disease. Chickens are infected through environmental exposure. Aspergillus
are opportunistic invaders, and healthy birds are usually resistant to infection unless they are exposed to a massive number in the environment or are vulnerable due to age, concurrent illness, chronic inflammatory condition (such as bumblefoot or other prolonged condition) or stress. Sometimes multiple flock members become infected at the same time from exposure to the same source.