Which set of diseases should be considered in the differential diagnosis for a pet bird with ruffled feathers, diarrhea, and mild respiratory and neurologic signs?

• A. Avian influenza, Pacheco's disease, Salmonellosis, & Exotic Newcastle's Disease
• B. Aspergillosis, Chlamydiosis, Avian influenza, Calcium deficiency, and Salmonellosis
• C. Lead toxicity, Pacheco's disease, avian influenza, exotic Newcastle's disease and aspergillosis
• D. Avian influenza, Pacheco's disease, salmonellosis, and exotic Newcastle's disease

Answer: (A)

When a pet bird shows ruffled feathers with diarrhea, plus mild respiratory and neurologic signs, think of illnesses that can cause multi-system disease affecting the GI tract, airways, and nervous system. The best differential set includes diseases that are known to produce a combination of these signs and are commonly considered in birds.

Avian influenza can cause respiratory involvement and, depending on the strain, neurologic signs; it’s a top infectious concern because it can spread quickly and has zoonotic importance. Pacheco’s disease, caused by a herpesvirus, often leads to systemic illness with liver involvement and can present with malaise, ruffled feathers, and non-specific GI signs like diarrhea, making it a key consideration in psittacine birds. Salmonellosis directly causes diarrhea and can lead to septicemic, multi-organ disease, which matches the GI and systemic aspects observed. Exotic Newcastle’s disease, another avian virus, frequently presents with respiratory and neurologic signs and is highly contagious, making it an essential part of the differential in birds with these symptoms.

Other options include diseases or conditions that don’t align as neatly with the full pattern. For example, calcium deficiency is nutritionally driven and not typically tied to an acute multi-system presentation with neuro signs. Lead toxicity can cause GI and neurologic signs but is a toxin rather than an infectious differential; aspergillosis and chlamydiosis are important respiratory diseases but don’t as reliably encompass the diarrhea and the combined respiratory-neurologic picture seen here.

So, focusing on infectious diseases that commonly produce respiratory, GI, and nervous system signs in birds yields avian influenza, Pacheco’s disease, Salmonellosis, and Exotic Newcastle’s disease as the most appropriate differential set.