Bovine Listeriosis Study Guide

Overview and Clinical Importance

Listeriosis (also known as Circling Disease or Silage Sickness) is a sporadic but serious bacterial infection caused by Listeria monocytogenes, a gram-positive, facultatively anaerobic, intracellular coccobacillus. The disease primarily manifests as encephalitis or meningoencephalitis in adult cattle, though it can also cause abortion and septicemia. This condition is particularly important for the NAVLE because it requires differentiation from other neurological diseases including rabies, polioencephalomalacia, and thromboembolic meningoencephalitis.

Listeriosis is a zoonotic disease with significant public health implications. Veterinarians treating affected cattle must take appropriate precautions, as humans can become infected through contaminated milk or direct contact with infected animals and tissues. The disease is most commonly associated with feeding poorly preserved silage with a pH greater than 4.0 to 5.5.

Etiology

Causative Organism

Listeria monocytogenes is the primary causative agent. Key characteristics include: