Which disease primarily affects the respiratory system?

• A. Avian influenza
• B. Marek's disease
• C. Aspergillosis
• D. Newcastle disease

Answer: (C)

Aspergillosis is a fungal infection that primarily targets the respiratory system in birds. It is caused by Aspergillus species, usually inhaled from moldy bedding, dusty air, or contaminated feed. Once the spores lodge in the airways, they form nodules in the lungs and air sacs, leading to coughing, nasal discharge, wheezing, and labored breathing. Because the disease mainly involves the airways and lungs, respiratory symptoms are the hallmark, which is what makes it the best fit for a question asking about primary respiratory involvement.

The other diseases listed have different primary targets or patterns. Marek's disease mainly affects nerve tissue and the immune system. Newcastle disease can cause respiratory signs but often also affects the nervous system and can be systemic. Avian influenza can involve multiple body systems, though respiratory involvement is common; however, aspergillosis is distinguished by being a chronic, localized infection centered in the respiratory tract, not primarily a systemic viral disease. Prevention focuses on reducing exposure to mold and spores through good ventilation, dry, clean housing, and prompt antifungal treatment if infection is suspected.