Which of the following is/are a differential for a pet bird with ruffled feathers, diarrhea, mild respiratory signs and neurologic signs?

• A. Aspergillosis, chlamydiosis, avian influenza, calcium deficiency, and salmonellosis
• B. Avian influenza, encephalomalacia, and virulent Newcastle’s disease, systemic organ disease, and parasitism
• C. Lead toxicity, Pacheco’s disease, avian influenza, virulent Newcastle’s disease and aspergillosis
• D. Avian influenza, Pacheco’s disease, salmonellosis, and virulent Newcastle’s disease

Answer: (D)

When a pet bird shows a mix of ruffled feathers, diarrhea, mild respiratory signs, and neurologic signs, think of diseases that can affect multiple organ systems and spread beyond one body system. The strongest differential set includes avian influenza, Pacheco’s disease, salmonellosis, and virulent Newcastle disease because each can produce a combination of gastrointestinal, respiratory, and neurological signs in birds.

Avian influenza can cause respiratory manifestations and systemic involvement, and neurologic signs can appear with certain strains or advanced disease, making it a relevant differential for multisystem signs. Pacheco’s disease, caused by a herpesvirus in parrots, commonly presents with acute illness that can include gastrointestinal signs like diarrhea, and hepatic involvement can lead to systemic illness with potential neurologic manifestations. Salmonellosis is a bacterial infection that characteristically causes diarrhea and can progress to septicemia, which may involve the nervous system and other organs, aligning with the observed signs. Virulent Newcastle disease frequently causes respiratory and GI symptoms and has pronounced neurologic signs such as tremors, incoordination, and paralysis, fitting the neuro component of the presentation.

The other options mix diseases that don’t consistently produce the full combination of signs seen here. For example, some include primarily respiratory or ocular diseases, or include a nutritional deficiency or non-contrasting elements that don’t explain the neurologic signs as well.