Which of the following diseases affects the respiratory system?

Aspergillosis is a fungal infection that primarily affects the respiratory system of birds, including falcons. The disease is caused by the Aspergillus fungus, which can be found in various environments, often in decaying organic material or dust. When birds are exposed to this fungus, they can develop respiratory issues such as coughing, wheezing, and difficulty breathing. The condition can lead to serious complications if not treated, as it can cause pneumonia and other respiratory diseases.

In contrast, the other diseases listed pertain to different systems or issues. Coccidiosis is a parasitic infection affecting the gastrointestinal tract, primarily resulting in diarrhea and digestive upset. Frounce, also known as thrush or candidiasis, is a type of infection that affects the mouth and throat, often associated with a protozoan parasite but not primarily respiratory. Bumblefoot is a condition that affects the feet of birds, often leading to sores and infections, unrelated to respiratory health. Understanding these distinctions is key to recognizing the impact of various diseases on bird health, particularly in the context of falconry.