In a flock with acute mortality and a range of signs from none to conjunctivitis, depression, neurologic and/or respiratory signs, which diagnoses should be included in the differential?

In a flock with acute mortality and a range of signs from none to conjunctivitis, depression, neurologic and/or respiratory signs, which diagnoses should be included in the differential?

• A. Highly pathogenic avian influenza and Newcastle disease
• B. Marek's disease and Infectious laryngotracheitis
• C. Fowl cholera and management problems
• D. A, B, and C

Answer: (D)

When mortality is sudden and the flock shows a wide range of signs—from eye involvement to depression, neurologic or respiratory signs—the differential must cover multiple pathogen types and even noninfectious problems. Highly pathogenic avian influenza and Newcastle disease can both cause abrupt death and a mix of signs, including conjunctivitis, respiratory distress, and nervous system involvement, so they are essential to consider. Marek’s disease can present with neurologic abnormalities and ocular signs as well, and Infectious laryngotracheitis commonly causes conjunctivitis along with coughing and respiratory signs. Fowl cholera is a classic septicemic cause of sudden death and can present with depression and respiratory or systemic signs in an outbreak. Management problems, such as poor ventilation, heat or cold stress, and nutritional deficits, can mimic disease and contribute to sudden mortality as well. Because each group can produce the described clinical picture, all should be included in the differential. That broad approach ensures you don’t miss a plausible cause just because it isn’t the most common culprit in a given outbreak.

When mortality is sudden and the flock shows a wide range of signs—from eye involvement to depression, neurologic or respiratory signs—the differential must cover multiple pathogen types and even noninfectious problems. Highly pathogenic avian influenza and Newcastle disease can both cause abrupt death and a mix of signs, including conjunctivitis, respiratory distress, and nervous system involvement, so they are essential to consider. Marek’s disease can present with neurologic abnormalities and ocular signs as well, and Infectious laryngotracheitis commonly causes conjunctivitis along with coughing and respiratory signs. Fowl cholera is a classic septicemic cause of sudden death and can present with depression and respiratory or systemic signs in an outbreak. Management problems, such as poor ventilation, heat or cold stress, and nutritional deficits, can mimic disease and contribute to sudden mortality as well.

Because each group can produce the described clinical picture, all should be included in the differential. That broad approach ensures you don’t miss a plausible cause just because it isn’t the most common culprit in a given outbreak.